TEDS Data Dictionary

TEDS Spin-Offs and Sub-Studies

This page describes sub-studies that have involved relatively small subsets of the TEDS families.

A spin-off study generally refers to a research study involving a selected sub-sample of TEDS twins, administered and funded independently of the main TEDS studies. The PI of the spin-off is generally a collaborator who is not part of the TEDS team. Some spin-offs have been administered within KCL (for example, E-Risk, ECHO, SAIL, the autism studies) while a few have been administered at other universities (for example, Eating, OSCCI). Except in unusual cases where the spin-off has been administered within TEDS, the spin-off study data are the intellectual property of the study's PI, not of TEDS, and cannot be shared by TEDS.

Sub-studies more generally include not just the spin-offs but also relatively small studies within TEDS, involving selected sub-samples of twins. Where spin-off studies have been administered by TEDS, the data may in some cases be shared by TEDS with collaborating researchers. Also, materials such as information sheets, consent forms and questionnaires have generally been retained in these cases. Where available, these are reproduced in pdf documents which are linked in the relevant sections of the page below. Where the data have been retained within TEDS, some documentation of the datasets is provided below in the form of annotated pdfs, in so far as the relevant information is available.

In a few cases, TEDS-administered sub-studies have been fully documented within this data dictionary, as parts of a broader study. In these cases, there are links to the relevant study pages. Examples include the 4 year in-home visit study, the 14 year SLQ study and the age 19/20 web studies (perception, spatial, FFMP).

To find out more about a given study, click on one of the links in the table below to go to a table of information about each study. Alternatively, simply scroll down the page, where studies are listed in alphabetical order of study name. The tabulated information shown for each study includes:

Study name, PI, and administrative location
Dates when the study took place, given as a range of years
Information about the sample: number of families included (for invitation not necessarily participation), TEDS cohorts that were involved.
Outline of sample selection and exclusion criteria
Outline of the types of data collected
Whether or not the data are available for sharing by TEDS
Links to relevant documents, if available.

Main area of study	Spin-off study name	Year started
Autism	Autism (SCQ)	2001
	DOH	2003
	DAWBA	2005
	SRS (SRS, SRS-2 and SRS-3)	2008 (phase 1), 2013 (phase 2), 2017 (phase 3)
	Autism Speaks (GEMS)	2009
Hyperactivity, ADHD	SAIL	2003
	PHAD	2003
	EEG (NEAAT)	2009
	IDEAS	2015
Anxiety	Anxiety	2000
	ECHO	2002
	FLARe	2019
Psychopathy traits	MRI Conduct	2005
Language development	OSCCI	2000 (phase 1) and 2003 (phase 2)
	Stories (TEDS study, age 9)	2002
	SLQ (TEDS study, age 14)	2008
	Language telephone tests (TEDS study, age 14)	2008
	SLI	2011
	SLA	2012
Cognitive abilities	In-home tests (TEDS study, age 4)	1998
	LINCS	2005
	MRI Maths	2005
	Perception (TEDS study, age 19)	2013
	Spatial (Three consecutive TEDS studies, age 19-20: Bricks, Kings Challenge, Navigation)	2015
Eating, diet, lifestyle, health	Eating Study (Eating-1 and Eating-2)	1998 (phase 1) and 2005 (phase 2)
	Eating Questionnaire	2005
	Weight Discordance (Eating-3)	2006
	Stuttering	2006
	Twitter (Social Media)	2013
	Myopia	2012
	Music Quotient	2013
	Fashion, Food and Music Preferences (FFMP, TEDS study, age 19)	2015
Gene expression	RNA	2007
Gene expression	Biomarkers	2010
MZ discordance in achievement	Diary	2005
MZ discordance in achievement	Nuffield	2012
Siblings	Young Sibs	1997
Environmental risk	E-Risk	1998
Adolescent-parent attachment	Attachment	2010
Wellbeing	Wellbeing	2011
Wellbeing	Daily Mood	2014
Engagement in TEDS	Engagement	2014
Being a twin	TAMBA	2010

Anxiety

Study names:	Anxiety, Emotions and Development Study
Principal investigator:	Patrick Bolton
Location:	IOP (KCL)
Focus of study:	Anxiety traits
Year(s) of study:	2000 to 2002
Number of TEDS families:	1169
TEDS cohorts:	1994 and 1995
Families excluded from sample:	Withdrawn No TEDS 1st contact data Medical exclusions and perinatal outliers Unknown zygosity E-Risk families No TEDS data at 4
Selection criteria:	Selection was based on a number of anxiety measures in the TEDS 4 year dataset. There were several sample groups, possibly including controls.
Data collection:	Parent-completed booklets administered by post, followed up with telephone interviews.
Data available in TEDS:	No
Documents:	-

Attachment

Study names:	Attachment Study
Principal investigator:	Pasco Fearon
Location:	SGDP Centre, IOP (KCL) and Anna Freud Centre, London (study staff operation from both locations)
Focus of study:	Adolescent-parent attachment
Year(s) of study:	2010 to 2012
Number of TEDS families:	1265
TEDS cohorts:	School cohorts 3 and 4 (twins born between September 1995 and December 1996)
Families excluded from sample:	Withdrawn Inactive Medical exclusions and special cases Address and phone problems E-Risk families
Selection criteria:	Same-sex twin pairs Initial selection was families living in London or nearby counties (Middlesex, Kent, Surrey, East & West Sussex, Berks, Hants, Wilts, Bucks, Berks, Beds, Oxon, Herts, Essex, Cambs) Later topped up with families having good rail links to London (Avon, West Midlands, other parts of the Midlands and the north and east of England)
Data collection:	Parent and twin booklets sent by post. In-person visits, either to the SGDP Centre or to the Anna Freud Centre or to the families' homes, for twin attachment interviews (with videos).
Data available in TEDS:	No
Documents:	-

Autism

Study names:	Autism Study, SCQ study
Principal investigator:	Francesca Happe and Greg Wallace
Location:	IOP (KCL)
Focus of study:	Autistic traits
Year(s) of study:	2001
Number of TEDS families:	352 (72 cases, 280 controls)
TEDS cohorts:	All
Families excluded from sample:	Withdrawn E-Risk families OSCCI families ECHO families No TEDS data at 4 (for controls)
Selection criteria:	Cases: twins known or suspected to have autism/ASD from parent reports Controls: matched and unmatched categories based on 4 year data; also Downs syndrome twins
Data collection:	Parents questionnaire (SCQ) administered by post or by phone
Data available in TEDS:	No
Documents:	-

Autism Speaks

Study names:	Autism Speaks, GEMS
Principal investigator:	Angelica Ronald
Location:	Administered by TEDS
Focus of study:	Autistic traits
Year(s) of study:	2009
Number of TEDS families:	298 (41 cases, 257 controls)
TEDS cohorts:	All
Families excluded from sample:	All groups: Withdrawn Ethnic origin not known to be white English not the only language used at home Overseas families Address and phone problems Special cases DZ twins, or unknown sex/zygosity Additional exclusions for control groups: No TEDS CAST data at 8 No TEDS 1st Contact data Suspected or known ASD cases Medical exclusions and perinatal outliers Birthweight difference between twins >1SD
Selection criteria:	MZ Cases: twins with autism/ASD confirmed by TEDS study (DAWBA or SRS). Two groups: concordant and discordant for ASD. Controls: selected on the basis of 8 year CAST scales. Four groups: discordant social, discordant non-social, discordant communication, concordant low-CAST. Control group 6 (concordant low-CAST): addresses in London and home counties only
Data collection:	Families visited the SGDP Centre to give samples of blood and saliva (for DNA and RNA)
Data available in TEDS:	No
Documents:	-

Biomarkers

Study names:	Biomarkers pilot
Principal investigator:	Andrea Danese
Location:	Administered by TEDS
Focus of study:	Gene expression
Year(s) of study:	2010 to 2011
Number of TEDS families:	798
TEDS cohorts:	School cohort 2 (twins born between September 1994 and August 1995)
Families excluded from sample:	Withdrawn families Inactive families and special cases Address and phone problems Medical exclusions, and other medical conditions considered case-by-case E-Risk families Analysis exclusions (no 1st Contact data, perinatal outliers, unknown zygosity, non-white ethnic origin, home language not English)
Selection criteria:	Same-sex twin pairs Families living in London or in south and east England (as far west as Somerset, Avon, Glos and Worcs, and as far north as W Midlands, Leics, Warks, Northants and Norfolk)
Data collection:	After an initial mailing of an information pack with consent form, families were contacted by phone to establish verbal consent and for health screening. Suitable families were sent twin questionnaires and kits for collecting saliva samples, all of which were returned by post.
Data available in TEDS:	Yes (questionnaires only). The twin questionnaire data were entered in TEDS, and are available in a double entered dataset for roughly 230 twin pairs. The biological data derived from saliva samples have not been retained in TEDS.
Documents:	Information sheet and twin questionnaire sent with the initial pack. Annotated twin questionnaire showing dataset variable coding.

Daily Mood

Study names:	Daily Mood
Principal investigator:	Yao Zheng (supervised by Robert Plomin)
Location:	Administered by TEDS
Focus of study:	Wellbeing/mood
Year(s) of study:	2014
Number of TEDS families:	610
TEDS cohorts:	School cohort 4 (twins born between September and December 1996)
Families excluded from sample:	Withdrawn families Inactive families and special cases Address and phone problems Overseas families Medical exclusions and special cases Unknown zygosity
Selection criteria:	Same-sex twin pairs
Data collection:	On line and verbal consents were collected from the parents of the selected families. Twins of the consenting families were then invited to log in daily, at roughly the same time each day, for 40 consecutive days. On each of these days, twins were asked to complete a brief on line questionnaire relating to their moods. The same 10 items were presented every day, although the order of the items was randomised each day. The questionnaire could only be completed between 3pm and 3am each day.
Data available in TEDS:	Yes. The electronic web data were collected on the TEDS web server, and are available in a double entered dataset of 275 twin pairs. Yao Zheng should be included as co-author in any collaborative project.
Documents:	Information sheet as linked to the twin web consent page. Annotated twin web questionnaire showing dataset variable coding.

DAWBA

Study names:	DAWBA (Development and Well Being Assessment), Social Skills and Relationships
Principal investigator:	Francesca Happe
Location:	Administered by TEDS
Focus of study:	Autism
Year(s) of study:	2005 to 2007
Number of TEDS families:	433
TEDS cohorts:	All
Families excluded from sample:	Withdrawn families
Selection criteria:	EITHER autism/ASD known or suspected from parent reports OR possibility of autism/ASD suggested by high 8 year CAST scores
Data collection:	Parent telephone interviews conducted using the DAWBA instrument
Data available in TEDS:	No
Documents:	Information sheet sent with the initial postal invitation.

Diary

Study names:	Diary Study
Principal investigator:	Kathryn Asbury
Location:	Administered by TEDS
Focus of study:	School environments and achievement
Year(s) of study:	2005
Number of TEDS families:	145 (25 in feasibility study, 120 in pilot study)
TEDS cohorts:	School cohort 2 (twins born between Sep-94 and Aug-95)
Families excluded from sample:	Withdrawn Medical exclusions Families involved in any other current spin-off study Overseas families Phone problems
Selection criteria:	MZ twin pairs Both twins known to be taught in the same classroom
Data collection:	Twin telephone interviews daily over a period of two weeks (10 consecutive school days)
Data available in TEDS:	No
Documents:	Script showing the questions asked in twin interviews each day. Annotated script showing dataset variable coding.

DOH

Study names:	DOH (Department of Health) Study, Thinking and Feeling study
Principal investigator:	Essi Viding
Location:	Administered by TEDS
Focus of study:	Theory of Mind, in relation to verbal ability and ASD traits, with cases selected on psychopathic traits.
Year(s) of study:	2003 to 2004
Number of TEDS families:	1645 (769 cases, 876 controls)
TEDS cohorts:	School cohorts 1 and 2 (twins born Jan-94 to Aug-95)
Families excluded from sample:	Withdrawn Medical exclusions E-Risk families OSCCI families Overseas families Phone problems No TEDS teacher data at 7 Unknown twin sex
Selection criteria:	Cases: high scores in 9 year teacher callous-unemotional scale Controls: low scores in 9 year teacher callous-unemotional scale
Data collection:	Parents and twins were interviewed by telephone (administered by TEDS callers). The twin interview data were coded and entered in TEDS. Parent interview data were recorded using the "DAWBA" instrument, which is not documented in TEDS. In a small number of cases, questionnaire data were collected from twins' teachers, if not already collected during the preceding TEDS 9 Year study. This helped to categorise participating families as cases or controls. These additional teacher data have not been retained in TEDS.
Data available in TEDS:	Yes: coded twin interview data only, in a dataset of roughly 1200 twin pairs. The DAWBA parent interview data are not available. Essi Viding should be included as co-author in any collaborative project.
Documents:	Script showing the questions asked in twin interviews. Scoring rules for the Theory of Mind, Moral and Conventional, and Emotion Attribution measures in the twin interviews. Annotated script showing dataset variable coding for the twin interview data.

Eating Questionnaire

Study names:	Eating Questionnaire
Principal investigator:	Jane Wardle
Location:	Administered by TEDS, data sent to UCL.
Focus of study:	Eating/diet/weight
Year(s) of study:	2005
Number of TEDS families:	12212
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Inactive Address Problems
Selection criteria:	The questionnaire was sent to the entire sample of contactable TEDS families.
Data collection:	Parent questionnaire sent by mail. The data from returned questionnaires were entered by optical scanning.
Data available in TEDS:	Yes. The double entered dataset contains data from nearly 6000 parents. Any collaborative project should involve the research team at UCL.
Documents:	Questionnaire, completed by parents. Annotated questionnaire showing dataset variable coding.

Eating Study

Study names:	Eating Study, Eating-1 (phase 1), Eating-2 (phase 2)
Principal investigator:	Jane Wardle
Location:	University College, London
Focus of study:	Eating/diet/weight
Year(s) of study:	1998 to 2005 (Phase 1: 1998-99; Phase 2: 2005)
Number of TEDS families:	861 in phase 1 (531 controls, 330 cases), 204 in phase 2 (109 controls, 95 cases)
TEDS cohorts:	1994, 1995
Families excluded from sample:	Exclusion criteria not recorded for phase 1. Phase 2 families were a subset of the phase 1 families, with these exclusions: Withdrawn Medical exclusions Not visited in phase 1
Selection criteria:	Phase 1 cases: 3 and 4 year parent weights overweight/obese Phase 1 controls: 3 and 4 year parent weights normal Phase 2: subset of phase 1 cases and controls (see exclusions above)
Data collection:	Home visits for face-to-face testing.
Data available in TEDS:	No
Documents:	-

ECHO

Study names:	ECHO (Emotions, Cognitions, Heredity and Outcome)
Principal investigator:	Thalia Eley
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Anxiety
Year(s) of study:	2002 to 2005 (Phase 1: 2002-03; Phase 2: 2004-05)
Number of TEDS families:	374 (307 cases, 67 controls)
TEDS cohorts:	1994, 1995
Families excluded from sample:	Withdrawn Medical exclusions E-Risk families OSCCI families No TEDS parent data at 7
Selection criteria:	Address in south-east England Cases: high scores in 7 year parent anxiety scales Controls: low scores in 7 year parent anxiety scales
Data collection:	Families visited the SGDP Centre for face-to-face testing. DNA collected on visit.
Data available in TEDS:	No
Documents:	-

EEG

Study names:	EEG (electroencephalogram study), NEAAT (Neurophysiology of Attention and Activity in Twins), Centre Study
Principal investigator:	Grainne McLoughlin
Location:	SGDP Centre, IOP (KCL)
Focus of study:	ADHD
Year(s) of study:	2009 to 2010
Number of TEDS families:	301 (230 cases, 71 controls)
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Address and phone problems Overseas families E-Risk families SRS families Autism Speaks families Previously refused to give DNA samples Medical and other special cases
Selection criteria:	Address in south-east England given higher priority (families from further afield included where necessary) Cases (4 groups): MZ and DZ, concordant and discordant for ADHD, based on TEDS data at various ages Controls (2 groups): MZ and DZ, no ADHD indications
Data collection:	Families visited the SGDP Centre for face-to-face testing, including EEG measurements and questionnaires. DNA (blood and saliva) collected on visit.
Data available in TEDS:	No
Documents:	-

Engagement

Study names:	Engagement
Principal investigator:	Robert Plomin
Location:	TEDS
Focus of study:	Engagement of twins in TEDS activities, use of social media
Year(s) of study:	2014
Number of TEDS families:	393 (250 "engaged", 143 "disengaged")
TEDS cohorts:	School cohort 1
Families excluded from sample:	Withdrawn No email addresses recorded
Selection criteria:	"Engaged" sample: both twins had participated in the Perception web study in 2013 and had email addresses. "Disengaged" sample: only one twin had participated in the Perception web study, although both had been invited and both had email addresses.
Data collection:	Web questionnaires. The "Engaged" twin pairs were presented with a longer "SE" questionnaire. The "Disengaged" twin pairs were presented with a shorter "SD" questionnaire, in one of two versions: one version designed for the "disengaged" twin, and the other version designed for the "engaged" twin. The two versions of the SD questionnaire had essentially the same questions but with modified wording: disengaged twins were asked about themselves, while engaged twins were asked about their disengaged cotwins.
Data available in TEDS:	Yes. The SE questionnaire dataset has doubled entered data for roughly 60 twin pairs and 60 unpaired twins. The SD questionnaire dataset has unpaired data for roughly 60 twins (40 engaged and 20 disengaged).
Documents:	Engagement questionnaires, document including all three versions. Annotated questionnaire showing variables in the SE and SD datasets. Engagement information sheet.

E-Risk

Study names:	E-Risk (Environment-Risk), TEDS-Environment Includes sub-sample studies: Germ-Fighter Study (150 families, in 2009), Peers Study (87 families, in 2007)
Principal investigator:	Terrie Moffitt and Avshalom Caspi
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Environmental risk
Year(s) of study:	1998 onwards
Number of TEDS families:	1116
TEDS cohorts:	1994, 1995
Families excluded from sample:	Withdrawn No TEDS 1st Contact data
Selection criteria:	Same-sex twin pairs Cases (high risk): mother had her first child when she was 20 years or younger Controls: mother ages representative of general population
Data collection:	Home visits at several ages for face-to-face testing. DNA collected during visits. Teacher questionnaires at several ages; school visits for testing involving teachers at age 12.
Data available in TEDS:	No
Documents:	-

Fashion, Food and Music Preferences

Study names:	Fashion, Food and Music Preferences (FFMP), Fashion web study
Principal investigator:	Andrea Smith (UCL) compiled the measures. The study was administered in TEDS with Robert Plomin as PI.
Location:	Administered at the SGDP Centre, IOP (KCL), in collaboration with Andrea Smith (UCL)
Focus of study:	Twin preferences for types of fashion, food and music
Year(s) of study:	2015
Number of TEDS families:	3166
TEDS cohorts:	School cohort 3
Families excluded from sample:	Withdrawn Medical exclusions Twins uncontactable by mail or email
Selection criteria:	All twins in this cohort were invited.
Data collection:	Web questionnaire, administered by TEDS and treated as a main TEDS study.
Data available in TEDS:	Yes. This sub-study has been treated as a major TEDS study, forming part of the 18 year dataset. There are data for roughly 1300 twin pairs plus 400 unpaired twins. Andrea Smith (UCL) should be included as a co-author in any collaborative project.
Documents:	See the 18 year study page for full documentation.

FLARe

Study names:	FLARe (Fear Learning and Anxiety Response)
Principal investigator:	Thalia Eley
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Anxiety responses
Year(s) of study:	2019
Number of TEDS families:	2957
TEDS cohorts:	All
Families excluded from sample:	Withdrawn No TEDS-21 data Specific medical conditions such as epilepsy, heart problems, neurological conditions Twins without viable email addresses Twins living outside the UK
Selection criteria:	Twin pairs were selected in which both twins had completed phases 1 and 2 of TEDS21 prior to October 2018 (the TEDS21 study was still in its closing stages when FLARe started).
Data collection:	Mobile phone app, using headphones, and involving responses to fear-conditioning stimuli.
Data available in TEDS:	No
Documents:	-

IDEAS

Study names:	IDEAS (Individual Differences in EEG in Young Adults Study)
Principal investigator:	Grainne McLoughlin
Location:	SGDP Centre, IOP (KCL)
Focus of study:	ADHD and its overlap with ASD
Year(s) of study:	2015 to 2019
Number of TEDS families:	1154
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Severe medical conditions and special cases Uncontactable twins Twins living outside the UK E-Risk families, except with prior agreement
Selection criteria:	Families who previously participated in the NEATT/EEG study (2009-2010) and/or in the SRS study (2008-2010) supplemented by new families in which one or both twins had high scores in measures of ADHD or ASD traits.
Data collection:	EEG measurements using mobile equipment, administered in visits to the twins' homes or in visit of twins to the SGDP Centre. Also, in-person interviews and questionnaires (for twins, not parents).
Data available in TEDS:	No
Documents:	-

In-Home Study

Study names:	In-Home Study, 4 Year In-Home Testing
Principal investigator:	Robert Plomin
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Language and cognitive testing
Year(s) of study:	1998 to 2001
Number of TEDS families:	992 Note that this was effectively treated as a main TEDS study, even though it involved only a subsample of the families.
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Medical exclusions and known hearing problems Address and phone problems Twins living outside the UK No 1st Contact data
Selection criteria:	Selected families had (recently) completed the 4 Year booklets. Selection was then based on the language and cognitive data from these booklets. Families were selected as 'lows' if either or both twins met specific criteria for low-scoring in either the Parca cognitive tests or the MCDI language measures. In addition to the 'lows', some 'control' families were selected in which neither twin met the 'low' criteria. Further explanation of selection can be found on the in-home study page.
Data collection:	A battery of cognitive and language tests, administered by TEDS researchers during visits to family homes. In addition, there was a parent questionnaire and researcher-based assessments of the home environment and aspects of twin behaviour.
Data available in TEDS:	Yes. This sub-study has been treated as a major TEDS study, forming the in-home dataset. There are data for roughly 800 twin pairs.
Documents:	See the in-home study page for full documentation.

Language telephone tests

Study names:	Language tests (part of the TEDS age 14 battery)
Principal investigator:	Emma Hayiou-Thomas
Location:	York
Focus of study:	Language/verbal abilities
Year(s) of study:	2008
Number of TEDS families:	649
TEDS cohorts:	School cohort 1
Families excluded from sample:	Withdrawn Severe medical conditions and special cases Phone problems Twins living outside the UK Families who had opted out of other 14 year study activities
Selection criteria:	Families in cohort 1 were selected if both twins had previously completed the language web tests at age 12.
Data collection:	Telephone tests administered by phone to twins and recorded onto audio CDs. The tests were administered in TEDS, then the CDs were transported to York University for transcription, coding and analysis.
Data available in TEDS:	No
Documents:	The actual tests are not documented here, but some details about the administration of the study can be found on the 14 year study page.

LINCS

Study names:	LINCS (Linking Cognitive Styles)
Principal investigator:	Francesca Happe
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Cognitive abilities
Year(s) of study:	2005
Number of TEDS families:	1393 (broadly unselected, no cases or controls)
TEDS cohorts:	1996
Families excluded from sample:	Withdrawn Medical exclusions and perinatal outliers E-Risk families OSCCI families SAIL families PHAD families Unknown twin sex or zygosity No TEDS 1st Contact data No TEDS data at 4 or 7
Selection criteria:	(none)
Data collection:	Twin computer activities at home (activities run from a CD sent by post; data retrieved via Internet). A minority of families were subsequently contacted by phone for parent and twin telephone interviews.
Data available in TEDS:	No
Documents:	-

MRI Conduct

Study names:	MRI Conduct, Emotions and Behaviour Neuroimaging Study, Psychopathy MRI
Principal investigator:	Essi Viding
Location:	SGDP Centre, IOP (KCL) and the MRI Unit, Maudsley Hospital
Focus of study:	Psychopathy traits
Year(s) of study:	2005 to 2006
Number of TEDS families:	195 (100 CU+CP, 38 CP-only, 57 controls)
TEDS cohorts:	School cohorts 1 and 2 (twins born between January 1994 and August 1995)
Families excluded from sample:	Withdrawn Overseas families Address and phone problems E-Risk families Medical exclusions and perinatal outliers Unknown twin sex or zygosity No TEDS 1st Contact data No TEDS data at 9
Selection criteria:	Same-sex male twins (MZ or DZ) Cases: high scores in combined parent-teacher CU (callous-unemotional) and/or CP (SDQ conduct problems) scales at 9 Controls: low CU and CP "Normal" scores for hyperactivity and emotion (parent/teacher SDQ at 9) and IQ ('g' at 9)
Data collection:	Families visited the MRI Unit (Centre for Neuroimaging Sciences, Maudsley Hospital) for twin MRI scans with test activities.
Data available in TEDS:	No
Documents:	-

MRI Maths

Study names:	MRI Maths, Quantitative Neuroimaging of Mathematics Ability, Maths Neuroimaging Study
Principal investigator:	Yulia Kovas
Location:	SGDP Centre, IOP (KCL) and the MRI Unit, Maudsley Hospital
Focus of study:	Mathematics abilities
Year(s) of study:	2005
Number of TEDS families:	68 (39 lows, 29 highs)
TEDS cohorts:	1994 and 1995
Families excluded from sample:	Withdrawn Medical exclusions and perinatal outliers E-Risk families OSCCI families ECHO families LINCS families SAIL families PHAD families Overseas families Unknown twin sex or zygosity No TEDS 1st Contact data No TEDS data at 7
Selection criteria:	Low or high maths teacher ratings at 7 Maths scores at 9 (teacher ratings) and 10 (web test) were also considered on a case-by-case basis "Normal" scores for hyperactivity (teacher SDQ at 7) and IQ ('g' at 7, or Ravens test at 10)
Data collection:	Families visited the MRI Unit (Centre for Neuroimaging Sciences, Maudsley Hospital) for twin MRI scans with test activities.
Data available in TEDS:	No
Documents:	-

Music Quotient Pilot

Study names:	Music Quotient pilot study
Principal investigator:	Marcel Zentner (York University)
Location:	Administered by TEDS as a pilot study with retest. The activities were located on a web server administered by York University.
Focus of study:	Musical abilities
Year(s) of study:	2013
Number of TEDS families:	100
TEDS cohorts:	School cohort 1 (twins born between January and August 1994
Families excluded from sample:	Withdrawn Medical exclusions and special cases Address and phone problems Inactive Twins live apart (not at parent address)
Selection criteria:	100 twin pairs were randomly selected from cohort 1.
Data collection:	Twins were invited individually (not as pairs) by post. The invitation included login details for participation in the web study. A single postal reminder was sent, two weeks after the initial invitation. Participating twins were rewarded with Flexecode vouchers. 45 early participants were re-invited for a re-test, with the same activities, two weeks after completing the initial test; these twins were contacted using email addresses collected in the initial testing; up to three email reminders were sent, and participants were again rewarded with vouchers. Participating twins were asked for feedback at the end of the web activities. Non-participating twins were contacted for feedback about why they chose not to take part.
Data available in TEDS:	No.
Documents:	-

Myopia

Study names:	Myopia Study
Principal investigator:	Katie Williams, Chris Hammond
Location:	Administered partly by TEDS and partly by Katie Williams at St Thomas' Hospital
Focus of study:	Cognitive, behavioural, environmental and genetic associations with myopia
Year(s) of study:	2012
Number of TEDS families:	2625
TEDS cohorts:	School cohorts 2, 3 and 4 (twins born between September 1994 and December 1996)
Families excluded from sample:	Withdrawn Medical exclusions and special cases Address and phone problems Inactive Overseas (except for Eire) Not involved in the concurrent wave of the Wellbeing Study Not involved in more than one other concurrent or recently concluded sub-study (E-Risk, Attachment, Biomarkers, SLI, SLA, Wellbeing Pilot)
Selection criteria:	Twin pairs were selected if they met either or both of the following criteria: In cohort 2, one or both twins completed the "About You" web questionnaire at age 16 (this questionnaire included eyesight questions) In any cohort, either twin was in the discovery sample of genetic data from the WTCCC study
Data collection:	TEDS sent consent forms and questionnaires to the families; these were returned to TEDS, then forwarded to Katie Williams at St Thomas' Hospital. For consenting families, Katie Williams used the questionnaire information to contact opticians, in order to collect eye test prescription results.
Data available in TEDS:	No, except for the screening questions about eyesight in the 16 year web dataset.
Documents:	Combined letter, consent and initial questionnaire and the information sheet sent in the invitation pack.

Nuffield

Study names:	Nuffield Study
Principal investigator:	Kathryn Asbury
Location:	Administered partly by TEDS and partly by Kathryn Asbury at York University
Focus of study:	Discordance in MZ twin pairs
Year(s) of study:	2012 to 2014
Number of TEDS families:	2316
TEDS cohorts:	School cohorts 2 and 3 (twins born between September 1994 and August 1996)
Families excluded from sample:	Withdrawn Inactive Medical exclusions and special cases Address and phone problems Overseas Cohort 1 (because of concurrent 18 Year study) Cohort 4 (had not yet taken their GCSEs in 2012/13) Involved in other concurrent sub-studies (e.g. Wellbeing, E-Risk)
Selection criteria:	Phase 1 (parent and twin questionnaires): MZ twin pairs Cohorts 2 and 3 Phase 2 (phone interviews): Discordant twin pairs selected by Kathryn on the basis of the questionnaire data collected in phase 1. Phase 3 (twin questionnaires), pilot and main study: Same-sex MZ and DZ pairs Cohort 3, aged 18 or over (born before March 1996).
Data collection:	In phase 1, 2162 families in cohorts 2 and 3 were sent parent and twin questionnaires which were returned to the TEDS office; the data from the questionnaires (consisting entirely of text responses) were entered and forwarded to Kathryn at York for coding and analysis. These data have not been retained in TEDS. In phase 2, 120 families selected from the phase 1 questionnaire data were contacted by telephone to arrange in-person interviews. The interviews were recorded and later transcribed and coded at York. These data have not been retained in TEDS. Responses from phases 1 and 2 were used to create a structured questionnaire for phase 3. In the phase 3 pilot study, 300 families from cohort 3 were sent twin questionnaires which were returned to the TEDS office. The data were coded and entered in TEDS then transferred to Kathryn at York. These data have not been retained in TEDS. The phase 3 main study used a significantly altered and shortened version of the pilot questionnaire. This questionnaire was sent to a larger sample of 2152 families, again from cohort 3, including those families who had participated in the phase 3 pilot. The data were entered by optical scanning. The dataset was transferred to Kathryn at York and a copy of the dataset was retained in TEDS.
Data available in TEDS:	Yes, for the phase 3 main study only. The questionnaire data form a double-entered twin dataset for roughly 900 twin pairs. Data have not been retained in TEDS for phases 1 and 2, nor for the phase 3 pilot study. Kathryn Asbury should be included as co-author in any collaborative project.
Documents:	Phase 1 parent questionnaire, twin questionnaire and information sheet. Phase 3 pilot twin questionnaire, main study twin questionnaire, coding in the main questionnaire.

OSCCI

Study names:	OSCCI (Oxford Study of Children's Communication Impairments) OSCCI-2 for phase 2 of study
Principal investigator:	Dorothy Bishop
Location:	University of Oxford
Focus of study:	Language development
Year(s) of study:	Phase 1: 2000 to 2003; Phase 2: 2003 to 2006
Number of TEDS families:	Phase 1: 747 (285 cases, 462 controls) Phase 2: 305 (all cases)
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Medical exclusions E-Risk families (phase 2) Address problems No TEDS data at 4 (for phase 1) or 7 (for phase 2)
Selection criteria:	Same-sex twin pairs White ethnic origin English is the only language spoken at home Phase 1: categorised as cases or controls on the basis of TEDS 4 year data Phase 2: EITHER cases from phase 1 OR low scores in the TEDS 7 year TOWRE reading test
Data collection:	Home visits for face-to-face testing. School visits for testing involving teachers.
Data available in TEDS:	No
Documents:	-

PHAD

Study names:	PHAD (Pathways to Hyperactivity and Attention Deficit), Hyperactivity Study
Principal investigator:	Eric Taylor
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Hyperactivity
Year(s) of study:	2003 to 2006
Number of TEDS families:	817 (all cases)
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Medical exclusions E-Risk families OSCCI families ECHO families Autism study (2001) families SAIL families No TEDS parent or teacher data at 7
Selection criteria:	Same-sex twin pairs High score in 7 year hyperactivity scales (parent and/or teacher) for one or both twins
Data collection:	Screening questionnaire (sent by post) followed by home visit involving computer activities. DNA collected on home visit. Visit followed up by MRI scan at the IOP in some cases.
Data available in TEDS:	No
Documents:	-

Perception

Study names:	Perception Study, Face Perception, Faces web study
Principal investigator:	Nic Shakeshaft, under the supervision of Robert Plomin
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Visual perception and memory
Year(s) of study:	2013
Number of TEDS families:	2382
TEDS cohorts:	School cohort 1 (plus 100 families from cohort 2 in the pilot phase)
Families excluded from sample:	Withdrawn Medical exclusions Twins uncontactable by mail or email
Selection criteria:	All twins in cohort 1 were invited, along with 100 randomly selected twin pairs from cohort 2. The study comprised a pilot phase with 100 twin pairs from each of cohorts 1 and 2, followed by a main study phase with the remainder of cohort 1. The measure was not changed after the pilot phase, and the dataset contains data from both the pilot and the main phase.
Data collection:	Web battery (tests and questionnaire), administered by TEDS and treated as a main TEDS study.
Data available in TEDS:	Yes. This sub-study has been treated as a major TEDS study, forming part of the 18 year dataset. There are data for just under 1000 twin pairs plus 300 unpaired twins. Nic Shakeshaft should be included as a co-author in any collaborative project.
Documents:	See the 18 year study page for full documentation.

RNA

Study names:	RNA Study, Gene Expression Study
Principal investigator:	Emma Meaburn
Location:	Administered by TEDS
Focus of study:	Gene expression
Year(s) of study:	2007
Number of TEDS families:	5
TEDS cohorts:	1994
Families excluded from sample:	Withdrawn Overseas families Medical conditions Involved in other spin-off studies
Selection criteria:	MZ twin pairs Discordant reading scores at 12
Data collection:	Families visited the SGDP Centre for face-to-face testing and blood sampling. Visits were repeated (with identical activities and blood sampling) later the same year for reliability testing.
Data available in TEDS:	No
Documents:	-

SAIL

Study names:	SAIL
Principal investigator:	Jonna Kuntsi
Focus of study:	ADHD
Location:	SGDP Centre, IOP (KCL)
Year(s) of study:	2003 to 2005
Number of TEDS families:	1444 (broadly unselected; no cases or controls)
TEDS cohorts:	School cohorts 3 and 4 (twins born between September 1995 and December 1996)
Families excluded from sample:	Withdrawn Medical exclusions and perinatal outliers E-Risk families OSCCI families ECHO families No TEDS data at 4 or 7 No TEDS 1st Contact data Unknown zygosity
Selection criteria:	Address in south-east England White ethnic origin
Data collection:	Families visited the SGDP Centre for face-to-face testing. DNA collected on visit. Parent questionnaire administered during visit. Teacher questionnaires administered by post.
Data available in TEDS:	No
Documents:	-

SLA

Study names:	SLA (Second Language Acquisition)
Principal investigator:	Philip Dale
Location:	Administered by TEDS
Focus of study:	Learning a second language (German)
Year(s) of study:	2012
Number of TEDS families:	146
TEDS cohorts:	School cohort 4 (twins born between September and December 1996)
Families excluded from sample:	Withdrawn Overseas families (except Eire) Uncontactable families (both phone and address problems) Medical exclusions and special cases Families in which either twin had previously learned either German or Dutch
Selection criteria:	The initial sample comprised families in which the parent had completed and returned the language questionnaire (SLQ) at age 14
Data collection:	Twins were asked to spend a minimum of 5 hours learning German using the 'Rosetta Stone' software package. Data were collected (on the Rosetta Stone server) by means of tests incorporated within the software package. The data comprised scores for tests at the first four levels of learning in the software. The scores at each level were for topics such as vocabulary, grammar, writing, listening and speaking. Data were collected from 26 twin pairs and 1 unpaired twin. The data from this pilot study were not fully documented and they have not been retained in TEDS.
Data available in TEDS:	No
Documents:	Information sheet

SLI

Study names:	SLI (Specific Language Impairment)
Principal investigator:	Philip Dale
Location:	Administered by TEDS
Focus of study:	Language impairment
Year(s) of study:	2011 to 2012
Number of TEDS families:	670
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Overseas families (except Eire) Uncontactable families (both phone and address problems) Medical exclusions
Selection criteria:	The initial sample comprised families who were visited in the TEDS 4 year In Home study (minus exclusions as above)
Data collection:	Short telephone test administered to twins.
Data available in TEDS:	Yes. The telephone test responses were scored and entered in TEDS, and are available in a double entered dataset for just over 400 twin pairs. Philip Dale should be included as co-author in any collaborative project.
Documents:	Twin interview script used by callers. Twin score sheet used by callers to record responses, annotated to show item response and score variables. Dataset variables including derivation of scores.

SLQ

Study names:	SLQ (Second Language Questionnaire)
Principal investigator:	Philip Dale
Location:	Administered by TEDS
Focus of study:	Second language acquisition
Year(s) of study:	2008 to 2011
Number of TEDS families:	10,936
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Address problems Medical exclusions and special cases
Selection criteria:	The initial intended sample was school cohort 1. However, over the following three years it was extended to cohorts 2, 3 and 4, hence included the entire TEDS sample. This was at least partly because the same questionnaire was used to collect KS3 assessment data.
Data collection:	Parent questionnaire.
Data available in TEDS:	Yes. This now forms part of the main TEDS 14 year dataset. There are data for roughly 3500 twin pairs. Philip Dale should be included as co-author in any collaborative project involving the second-language measures.
Documents:	See pages relating to the 14 year study.

Spatial

Study names:	Spatial web studies. Included three consecutive web studies: Bricks, Kings Challenge and Navigation.
Principal investigator:	Nic Shakeshaft, under the supervision of Robert Plomin
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Spatial cognitive abilities
Year(s) of study:	2015
Number of TEDS families:	2184 (Bricks), 3042 (Kings Challenge), 5509 (Navigation)
TEDS cohorts:	School cohorts 1 and 2
Families excluded from sample:	Withdrawn Medical exclusions Twins uncontactable by mail or email
Selection criteria:	Bricks: only families in which both twins had completed the entire battery of 16 year web tests. Kings Challenge: only families in which both twins had completed at least part of the 16 year web battery. Navigation: all twins in cohorts 1 and 2 were invited. Hence the sample was progressively widened from Bricks to Kings Challenge to Navigation, but all were within cohorts 1 and 2.
Data collection:	Batteries of web tests, administered as three independent studies by TEDS (and treated as a main TEDS study).
Data available in TEDS:	Yes. This sub-study has been treated as a major TEDS study, forming part of the 18 year dataset. There are data for roughly 1300 twin pairs (Bricks), 1100 pairs (Kings Challenge) and just under 1000 pairs (Navigation), plus varying numbers of unpaired twins. Nic Shakeshaft should be included as a co-author in any collaborative project.
Documents:	See the 18 year study page for full documentation.

SRS

Study names:	SRS (Social Relationships Study), SRS-2 (for phase 2), SRS-3 (for phase 3)
Principal investigator:	Francesca Happe
Location:	SGDP Centre, IOP (KCL)
Focus of study:	Autism
Year(s) of study:	Phase 1: 2008 to 2010 Phase 2 (SRS-2): 2013 to 2014 Phase 3 (SRS-3): 2017 to 2019
Number of TEDS families:	Phase 1: 1094 (222 cases, 171 unmatched controls, 701 matched controls) Phase 2: 219 (cases) Phase 3: 531 (cases and high-trait twins)
TEDS cohorts:	All
Families excluded from sample:	All families: Withdrawn Overseas families Phase 1 control families (matched and unmatched): E-Risk families OSCCI families Medical exclusions Analysis exclusions (perinatal, unknown sex/zygosity, no 1st Contact data, non-white ethnic origin) Address and phone problems
Selection criteria:	Cases (phases 1 and 2): all families with known or suspected autism/ASD, from parent contacts and from previous autism studies. Phase 3: additional cases from more recent family reports, plus high-trait twins from TEDS ASD trait measures in more recent studies. Phase 1 all controls (matched and unmatched): address in south-east England Phase 1 unmatched controls: low CAST scores at 8 Phase 1 matched controls: low IQ, special needs or learning difficulties (assessed from various sources)
Data collection:	Home visits for face-to-face twin testing and parent questionnaires (in phases 2 and 3, families had the option of visiting the SGDP Centre instead). Phase 1 cases followed up with a second home visit. DNA collected during visit. Teacher questionnaires administered by mail. Siblings assessed initially by postal questionnaire, then followed up at visit if suspected of autism/ASD.
Data available in TEDS:	No
Documents:	-

Stories

Study names:	Stories task from twin 9 year booklet
Principal investigator:	Bonny Oliver
Location:	Administered by TEDS
Focus of study:	Writing abilities
Year(s) of study:	2002 to 2004
Number of TEDS families:	4076
TEDS cohorts:	School cohorts 1 and 2
Families excluded from sample:	Withdrawn Address problems Medical exclusions
Selection criteria:	Twin booklets were sent to all families who had given initial consent to participating in the 9 year booklet study.
Data collection:	A measure within the twin booklet.
Data available in TEDS:	Yes. The hand-written stories were scanned and have been saved in pseudonymous pdf files, one per twin. Each such file is identified by its file name, which is the pseudonymous identifier for the twin. The scanned image within each file is of the hand-written story, with any other potentially identifying information removed. These scanned files exist for roughly 2800 twin pairs. Bonny Oliver should be included as co-author in any collaborative project.
Documents:	See pages relating to the 9 year study.

Stuttering

Study names:	Stuttering, Speech Fluency Study
Principal investigator:	Katharina Dworzynski
Location:	Administered by TEDS
Focus of study:	Stuttering
Year(s) of study:	2006
Number of TEDS families:	321
TEDS cohorts:	All
Families excluded from sample:	Withdrawn Medical exclusions and perinatal outliers No TEDS 1st contact data Languages other than English used at home Unknown twin sex/zygosity No TEDS data at 3, 4 or 7
Selection criteria:	Twins reported to have stuttering problems at 3, 4 or 7
Data collection:	Parents interviewed by telephone
Data available in TEDS:	No.
Documents:	Information sheet sent with the initial consent mailing. Rating scale used by callers to rate and code responses. (Unfortunately, no copy of the script or interview questions has been retained.)

TAMBA

Study names:	TAMBA, What is it like to be a twin?
Principal investigator:	Robert Plomin
Location:	Administered by TEDS
Focus of study:	Feelings about being a twin
Year(s) of study:	2010
Number of TEDS families:	122
TEDS cohorts:	all
Families excluded from sample:	Uncontactable families (withdrawn, address problems)
Selection criteria:	A subset of twin pairs participating in the Attachment sub-study, described elsewhere on this page.
Data collection:	This small study was carried out at the request of the Twins and Multiple Births Association (TAMBA). Questions were supplied by TAMBA and edited by TEDS researchers to create a brief paper questionnaire. Data from returned questionnaires were manually entered in the TEDS office. The data collection was not documented in detail. Apparently, the questionnaire was passed to staff involved in the Attachment sub-study (described elsewhere on this page), in the hope that participating Attachment families would also complete the TAMBA questionnaire.
Data available in TEDS:	Yes. The questionnaire data have been used to make a double-entered twin dataset for roughly 120 twin pairs.
Documents:	TAMBA questionnaire annotated to show dataset variables and coding

Twitter

Study names:	Twitter, Social Networks Study
Principal investigator:	Claire Haworth, Oliver Davis
Location:	Administered by TEDS
Focus of study:	Wellbeing measurements from Twitter feeds
Year(s) of study:	2013
Number of TEDS families:	1553
TEDS cohorts:	all
Families excluded from sample:	-
Selection criteria:	Twins from cohorts 2, 3 and 4 who recorded their Twitter usernames in the 16 Year Leap booklet. Twins from all cohorts who sent their Twitter usernames (by email) after an invitation to participate that was advertised in the 2012 TEDS newsletter.
Data collection:	Twins who had supplied valid Twitter usernames in the LEAP-2 booklet at age 16 (2012) were supplemented by a further request sent with the TEDS newsletter in 2013. These twins, and their co-twins, were asked to complete a Social Media questionnaire in 2013. This questionnaire was collected by TEDS, and entered by means of optical scanning. For twins found to have valid usernames, Tweets (Twitter messages) were collected and analysed programmatically without the need for further contact with the families. This latter part of the study was administered by Oliver Davis at UCL.
Data available in TEDS:	Yes (questionnaire only, not Twitter data). These questionnaire data are available in a double entered twin dataset, for roughly 1200 twin pairs. The data harvested electronically from Twitter are not available in TEDS.
Documents:	Twin questionnaire and the accompanying invitation letter and information sheet. Annotated version of the twin questionnaire, showing dataset coding. References for questionnaire measures.

Weight Discordance

Study names:	Weight Discordance Study, Eating-3
Principal investigator:	Jane Wardle
Location:	University College, London
Focus of study:	Eating/diet/weight
Year(s) of study:	2006
Number of TEDS families:	24
TEDS cohorts:	All
Families excluded from sample:	Families were apparently hand-picked by Joanna Ashcroft, then vetted by TEDS on a case-by-case basis.
Selection criteria:	Selection criteria are unclear, but they are based on the 2005 Eating Questionnaire. The selection is unrelated to the earlier Eating Study.
Data collection:	Telephone interviews with parents.
Data available in TEDS:	No
Documents:	-

Wellbeing

Study names:	Wellbeing
Principal investigator:	Claire Haworth
Location:	Administered by TEDS
Focus of study:	Twin wellbeing
Year(s) of study:	2011 to 2013
Number of TEDS families:	1552
TEDS cohorts:	School cohorts 3 and 4 (twins born between September 1995 and December 1996)
Families excluded from sample:	Withdrawn Inactive Address and phone problems Overseas Unknown twin sex Unknown zygosity (pilot sample and wave 2 only) Medical exclusions and special cases Perinatal outliers (pilot sample only) Missing SES data from 1st Contact (pilot sample only) Participants in other concurrent sub-studies (this varied between phases of the Wellbeing study; relevant sub-studies were Attachment, E-Risk, SLI, SLA)
Selection criteria:	Same-sex twin pairs Twins participated in the 12 year web study (pilot sample only) 113 families from cohorts 3 and 4 were selected for the pilot study in 2011; 437 families from cohort 4 were selected for wave 1 of the main study in late 2012; 1002 families from cohort 3 were selected for wave 2 in early 2013. The initial selection for the pilot study included 20 families in each of 10 groups (5 quintile groups for SES variable 'ases', each divided into two male and female groups). The families in each group were selected at random from larger available numbers meeting the criteria above. In the main study (waves 1 and 2), an initial pool of families was selected according to the criteria above. Equal numbers of male and female twin pairs were then selected randomly from this pool. In wave 2, as a further constraint, equal numbers of MZ and DZ twin pairs were selected.
Data collection:	A series of time-sensitive questionnaires, and requests to carry out practical wellbeing activities, was administered via the web over a period of 9 weeks. The activities were refined between the pilot study and the main study. In the main study, for twins, a questionnaire was administered in week 0, at the time of initial login, followed by further activities (questionnaires and other tasks) at weekly intervals for weeks 1, 2, 3, 4, 5 and 6, then a final questionnaire in week 9. For parents, the questionnaires were much shorter (with no practical activities) and only administered in weeks 0, 3, 6 and 9. Further details can be found in the documents linked below. The data were collected via a web application on the TEDS web server. In each family, the parent was required to log in and consent before each twin could proceed; and twins were then required to give their own consent. The text data entered by twins in certain activities were subsequently programmatically coded, but the text data and the resulting codes have not been retained; the coding process is not documented in TEDS.
Data available in TEDS:	Yes: for the main study only (not for the pilot study). The dataset contains data for roughly 450 families (parent and both twins). The variables are double entered. Claire Haworth should be included as co-author in any collaborative project.
Documents:	Weekly order of activities. Twin activities and parent activities. Timing and other rules.

Young Sibs

Study names:	Young Sibling Study
Principal investigator:	Robert Plomin
Location:	Administered by TEDS
Focus of study:	Comparison of non-twin siblings with twins
Year(s) of study:	1997 to 2004
Number of TEDS families:	1350
TEDS cohorts:	All
Families excluded from sample:	Younger siblings who were themselves twins In families with more than one younger sibling, only one was chosen for data collection (preferably the one closest in age to the twins) For the 7 year young sib study, sibs of twins who did not supply data at age 7 were excluded Withdrawn families Address/phone problems Families in which twins were medical exclusions
Selection criteria:	In general, all families of known young siblings of the appropriate age were contacted and asked to participate at each age (2, 3, 4 and 7).
Data collection:	Questionnaires and other instruments were equivalent to those used for the twin data collections at ages 2, 3, 4 and 7. At 2, 3 and 4, the child booklet was the same as for the respective twin studies (but the parent booklet was not used). At age 7, telephone interviews by TEDS staff were used to collect twin test data and child-specific measures from the parent questionnaire, as for the twins at age 7. Where parents gave consent, siblings' teachers were also contacted by post for the 7 year teacher questionnaire. All data were coded and entered within TEDS, as for the twin data.
Data available in TEDS:	Yes. The sibling datasets at ages 2, 3, 4 and 7 have been retained in a single dataset (not double entered because they are not twins). These datasets include essentially the same variables as in the equivalent twin datasets at these ages. The sibling datasets can be merged with the twin datasets by matching on the family identifier id_fam. There are data for roughly 500 siblings at age 2, 600 siblings at age 3 and 550 siblings at age 4; there are 275 siblings with data at all three ages. There are parent and child data for roughly 240 siblings at age 7, with additional teacher data for 175 of them.
Documents:	The materials used for the young sibling study (booklets, questionnaires, telephone tests) were the same as those used in the corresponding twins studies: see the 2 Year, 3 Year, 4 Year and 7 Year study pages for details. Outline of measures and variables included in the young sibling datasets.