CATSS18 - The Child and Adolescent Twin Study in Sweden (18 years)
CATSS18 - The Child and Adolescent Twin Study in Sweden (18 years)
Overview CATSS
The Child and Adolescent Twin Study in Sweden (CATSS) is an ongoing longitudinal twin study that targets all twins born in Sweden since July 1, 1992. Since 2004, parents of twins have been interviewed about the children's somatic and mental health and social environment in connection with their 9th birthday (CATSS9). At ages 15 (CATSS15) and 18 (CATSS18), twins and parents complete a web questionnaire that, in addition to assessments of somatic and mental health, includes measures of personality development and psychosocial adaptation. At the age of 24 (CATSS24), only twins participate in a web survey that mainly focuses on mental health.
CATSS18:
CATSS18 started in 2011. The study includes all 18-year-old twins and their parents, regardless of their participation in CATSS9 or CATSS15. The response rate is 50% for the twin survey and 40% for the parent survey. The sample comprises both identical (monozygotic) and fraternal (dizygotic) twins, including same-sex and opposite-sex pairs. The total number of participating twins (through parent and/or twin participation) is currently 22,000 out of 38,400 invited twins (December 2025). The combined response rate is 57%. Participants who have not yet provided a DNA sample via saliva are requested to do so. The saliva sample is used for zygosity determination and genotyping. Currently, 13,700 twins have been genotyped in CATSS18 (December 2025).
The question areas in the CATSS18 surveys are listed below. For detailed information about variables, visit strdata.se.
Question areas in parent survey:
ABCL - Adult Behavior Checklist
A-TAC - Autism - Tics, ADHD and other Comorbidities inventory (only Autism-questions)
Demography
Asthma
Eating disorders
LEC - Life Events Checklist
LSC-R - Life Stressor Checklist
MDQ - Mood Disorder Questionnaire
PCR - Parent Child Relationship
PPCP - Parents' Perception of Child's Peers
PLE - Psychotic-like Experiences
Parents physical activity
Social Interventions
Spare Time Activities
Question areas in twin survey:
AUDIT - Alcohol Use Disorders Identification Test
A-TAC - Autism - Tics, ADHD and other Comorbidities inventory (only Autism-questions)
BOCS - Brief Obsessive Compulsive Scale
CES-D - Center for Epidemiologic Studies Depression Scale
CMRS- Child Mania Rating Scale
Demography
DAWBA - Development and Well-Being Assessment
DUDIT - Drug Use Disorders Identification Test
DSM-IV Criteria for Major Depressive Episode
DCQ - Dysmorphic Concerns Questionnaire
EDI-2 - Eating Disorder Inventory - 2
Friends' Behavior
HRS-I - Hoarding Rating Scale-Interview
LEC - Life Events Checklist
LHA - Life History of Aggression
LSC-R - Life Stressor Checklist- Revised
Love Relationship
MDQ - Mood Disorder Questionnaire
Nicotine Use
PCR - Parent Child Relationship
Phobias
Physical Activity
PLE - Psychotic-like Experiences
Premenstrual syndrome
Quality of Friendship
SCARED - Screen for Child Anxiety Related Emotional Disorders
SRD - Self-Reported Delinquency
Sexuality
Social Interventions
Spare Time Activities
Synesthesia
TCI - Temperament and Character Inventory
YPI - Youth Psychopathic Traits Inventory
Weight & height
Go to data source
https://ki.se/en/research/research-infrastructure-and-environments/core-facilities-for-research/swedish-twin-registry-core-facility
Documentation files
Documentation files
- SMART (2009) - Best Practices for Asking Questions about Sexual Orientation on Surveys.pdf885.51 KiB
Citation and access
Citation and access
Data access level:
Creator/Principal investigator(s):
Research principal:
Data contains personal data:
Yes
Type of personal data:
Pseudonymised, health data, social security number, lifestyle, exposures, names, addresses, survey responses
Code key exists:
Yes
Sensitive personal data:
Yes
Citation:
Method and outcome
Method and outcome
Unit of analysis:
Population:
18-year-old twins born in Sweden on or after July 1, 1992.
Study design:
- Cohort study
- Observational study
Description of study design:
Data collection is conducted through a web survey. Until 2020, participants had the option to choose a paper survey if they preferred. Participation in the study is based on informed consent.
Sampling procedure:
Description of sampling:
All 18-year-old twins born in Sweden on or after July 1, 1992, according to the Medical Birth Registry (the National Board of Health and Welfare), and living in Sweden at the time of the study invitation are included. Twins who have declined further participation in the Swedish twin registry, have protected identity, have emigrated, or have passed away are excluded. Only complete twin pairs are invited to participate, although data from both complete twin pairs and individual twins are collected.
Time period(s) investigated:
Number of individuals/objects:
22000
Response rate/participation rate:
57%
Description of the response rate/participation rate:
The total number of participating twins (through the participation of twin and/or parent) is 22,000 out of 38,400 invited (December 2025), resulting in a response rate of 57%
Samples/material - Collected from scientific collection/biobank
Samples/material - Collected from scientific collection/biobank
Name:
KI Biobank
Type(s) of sample:
DNA from saliva
Data collection - Self-administered questionnaire
Data collection - Self-administered questionnaire
Mode of collection:
Self-administered questionnaire
Description of the mode of collection:
Paper or web questionnaire
Time period(s) for data collection:
2011-01 - Ongoing
Data collector:
- Karolinska Institutet
Opens a new window at ror.org.
ROR
Source of the data:
- Registers/Records/Accounts: Medical/Clinical
- Registers/Records/Accounts
Instrument
Instrument
Name:
EDI-2
Type:
Structured questionnaire
Description of the instrument:
The Eating Disorder Inventory (EDI) is a self-report questionnaire designed to assess the presence of eating disorders.
DOI: 10.1002/1098-108X(198321)2:23.0.CO;2-6
DOI: 10.1080/08039480500504537
Name:
LSC-R
Type:
Structured questionnaire
Description of the instrument:
The Life Stressor Checklist-Revised (LSC-R) is a self-report measure used to assess traumatic or stressful life events.
DOI: 10.1017/S0033291711003060
Name:
PLE
Type:
Structured questionnaire
Description of the instrument:
Psychotic-Like Experiences (PLE) - Five items adapted from the Diagnostic Interview Schedule for Children (DIS-C) are used to screen for psychotic-like experiences in children.
DOI: 10.1016/j.schres.2006.11.006
Name:
TCI
Type:
Structured questionnaire
Description of the instrument:
The Temperament and Character Inventory (TCI) is a self-report questionnaire based on Cloninger's psychobiological model of personality.
DOI: 10.1001/archpsyc.1993.01820240059008
DOI: 10.1016/0959-4388(94)90083-3
DOI: 10.1027/1015-5759.24.1.14
DOI: 10.1016/s0010-440x(98)90070-0
Name:
HRSI
Type:
Structured questionnaire
Description of the instrument:
Hoarding Rating Scale-Interview (HRS-I) is a five-item semi-structured interview designed to assess the features of compulsive hoarding (clutter, difficulty discarding, acquisition, distress and impairment).
DOI: 10.1016/j.psychres.2009.05.001
Name:
AUDIT
Type:
Structured questionnaire
Description of the instrument:
Alcohol Use Disorders Identification Test (AUDIT) is an instrument used to identify risky and harmful alcohol consumption. The instrument was originally developed by the World Health Organisation (WHO). The questions are asked in the parent survey and addresses the parent's own drug consumption.
DOI: 10.15288/jsa.1995.56.423
DOI: 10.1093/alcalc/37.3.245
DOI: 10.1111/j.1530-0277.1997.tb03811.x
DOI: 10.1111/j.1360-0443.1993.tb02093.x
Name:
DUDIT
Type:
Structured questionnaire
Description of the instrument:
Drug Use Disorders Identification Test (DUDIT) is an 11-item, self-administered screening instrument designed for drug-related issues. It provides information of the level of drug intake and selected criteria for substance abuse/harmful use and dependence, based on the ICD-10 and DSM-IV diagnostic systems. The questions are included in the parent survey and concerns the parent's drug consumption.
DOI: 10.1159/000081413
Name:
DCQ
Type:
Structured questionnaire
Description of the instrument:
DCQ is a self-report measure consisting of seven items that assess cognitive and behavioural aspects of dysmorphic concern. See document YATSS_Instrument_DCQ_svensk.pdf
DOI: 10.3109/00048679809062719
DOI: 10.1046/j.1440-1614.2001.00860.x
DOI: 10.3109/00048671003596055
Name:
PCR
Type:
Structured questionnaire
Description of the instrument:
Parent Child Relationship - An instrument assessing the relationship between parents and children.
DOI: 10.2307/1166050
DOI: 10.1037/0012-1649.30.1.32
Name:
MDQ
Type:
Structured questionnaire
Description of the instrument:
MDQ is a self-report questionnaire designed to screen for the presence of bipolar disorder.
DOI: 10.4088/jcp.v67n0518 (parental report)
DOI: 10.1176/appi.ajp.157.11.1873 (twin report)
Name:
LHA
Type:
Structured questionnaire
Description of the instrument:
The Life History of Aggression (LHA) scale is used for assessing trait aggression. It consists of 11 items that evaluate aggressive and antisocial behaviors that may have occurred during one's lifetime since age 13. The items are categorised into three subscales: aggression (5 items), self-directed aggression (2 items), and consequences/antisocial behavior (4 items).
DOI: 10.1016/s0165-1781(97)00119-4
Name:
SCARED
Type:
Structured questionnaire
Description of the instrument:
The SCARED (Screen for Child Anxiety Related Emotional Disorders) is a questionnaire designed to measure five dimensions of anxiety symptoms in children and adolescents.
DOI: 10.1097/00004583-200503000-00013
Name:
YPI
Type:
Structured questionnaire
Description of the instrument:
The Youth Psychopathic Traits Inventory (YPI) is a self-report measure of psychopathic personality traits in adolescents.
DOI: 10.1177/1073191106298286
Name:
TCI
Type:
Structured questionnaire
Description of the instrument:
The Temperament and Character Inventory (TCI) is a self-report questionnaire based on Cloninger's psychobiological model of personality. It is used to assess various aspects of temperament and character. The twin questionnaire includes 50 questions from this inventory.
DOI: 10.1001/archpsyc.1993.01820240059008
Name:
ASRS
Type:
Structured questionnaire
Description of the instrument:
ASRS is a self-report questionnaire consisting of 18 questions that assess symptoms of ADHD in adults according to DSM-IV criteria.
DOI: 10.1017/S0033291704002892
Name:
BOCS
Description of the instrument:
The Brief Obsessive–Compulsive Scale (BOCS) is a short self-report scale used for the assessment and diagnosis of obsessive-compulsive disorder (OCD).
DOI: 10.3109/08039488.2014.884631
DOI: 10.1016/0005-7967(94)00076-V
DOI: 10.1001/archpsyc.1989.01810110048007
Name:
DAWBA
Description of the instrument:
DAWBA (Development and Well-Being Assessment) is a tool used to diagnose and measure mental health problems in children and adolescents.
DOI: 10.1111/j.1469-7610.2000.tb02345.x
Name:
ABCL
Type:
Structured questionnaire
Description of the instrument:
The Adult Behavior Checklist (ABCL) is designed for assessing adaptive behaviour and internalising problems and externalising problems. The eight empirically based scales are as follows: Anxiety/Depression, Withdrawal, Somatic problems, Thought Problems, Attention Problems, Aggressive Behaviour, Rule Breaking Behaviour, Obsession-Compulsion.
Achenbach, T. M., & Rescorla, L. A. (2003). Manual for the ASEBA adult forms & profiles. Research Center for Children, Youth, & Families, University of Vermont, Burlington, VT, USA.
ISBN: 0938565869, 9780938565864
Name:
ATAC
Type:
Structured questionnaire
Description of the instrument:
Only the autism section of the ATAC questionnaire, used in CATSS9 (see separate data description), is used here. The questions were slightly modified to suit 18-year-olds.
DOI: 10.1192/bjp.187.3.262
DOI: 10.1186/1471-244X-10-1
DOI: 10.1186/1471-244X-13-233
Name:
DSM-IV MDE
Type:
Structured questionnaire
Description of the instrument:
Screening of depression based on the DSM-IV Criteria for Major Depressive Episode (MDE).
DOI: 10.1176/appi.books.9780890420249.dsm-iv-tr
Name:
CESD
Type:
Structured questionnaire
Description of the instrument:
The Center for Epidemiologic Studies Depression Scale Revised (CESD-R) assesses the frequency of depression-related symptoms experienced by respondents over the past week, including restless sleep, poor appetite, and feelings of loneliness.
DOI: 10.1016/j.psychres.2010.08.018
Name:
Friendship Quality
Type:
Structured questionnaire
Description of the instrument:
Questions to measure quality of friendship, adapted from the Parent-Child Relationship (PCR) scale.
DOI: 10.2307/1166050
Name:
Love Relationship
Type:
Structured questionnaire
Description of the instrument:
Love relationship questions, adapted from the Parent-Child Relationship (PCR) scale.
DOI: 10.2307/1166050
Name:
SRD
Type:
Structured questionnaire
Description of the instrument:
Self-reported Delinquency (SRD) - 25 questions to assess criminal or problematic behavior.
ISBN: 91-7153-983-2 (Swedish only)
Name:
Friends behavior
Type:
Structured questionnaire
Description of the instrument:
12 questions to assess substance use and criminal behavior among peers.
ISBN: 91-7153-983-2 (Swedish only)
Name:
CMRS
Type:
Structured questionnaire
Description of the instrument:
Child Mania Rating Scale (CMRS) - Diagnostic screening measure designed to identify symptoms of mania in children and adolescents.
DOI: 10.1002/jclp.20464
Name:
Sexuality
Type:
Structured questionnaire
Description of the instrument:
Four questions about sexual orientation. For more information on these questions, see the attached report "Best Practices for Asking Questions about Sexual Orientation on Surveys," created by the Sexual Minority Assessment Research Team (SMART).
Geographic coverage
Geographic coverage
Geographic location:
Geographic description:
Nationwide
Administrative information
Administrative information
Responsible department/unit:
Department of Medical Epidemiology and Biostatistics [C8]
Ethical Review
Ethical Review
Reviewer:
- Stockholm Ethical Review Board
Registration number:
Dnr: 2010/1410-31/1
Ethical review information:
The ethical application was approved on September 29, 2010.
Funding
Funding
Funding agency:
- Karolinska Institutet
Funding information:
Government grants
Funding agency:
- Swedish Research Council
Opens a new window at ror.org.
ROR
Award number:
2017-00641_VR
Award title:
Swedish twin registry
Funding information:
The Swedish Twin Registry (STR) is a national research register open to academic and industrial users. The mission of the STR is to provide a longitudinal research resource for epidemiological and molecular studies of twins. It was originally established in 1959 with particular focus on cardiovascular disease and cancer. Since then, interest has expanded to almost all common diseases and health problems. The STR has contacted all living Swedish born twins (over 9 years) and is the world´s largest twin registry. The current system of twin ascertainment, which has been running in perpetual mode for 13 years, is done through parental interviews when the twins turn 9 years of age. Nationwide questionnaires and telephone interviews have been conducted for different birth cohorts since the beginning of the 1960s. Longitudinal information about health and disease is obtained through regular linkages to the Swedish health registries. DNA from 55 000 twins and serum of 13 000 twins are stored at KI Biobank and is subject to use to new investigations and analyses. Genome-wide genotyping of more than 30 000 participants has been completed and genotypes can be used for co-analysis for different outcomes and characteristics. We apply for funds to keep up the register, continue the ascertainment of 9-year old twins and introduce, in parallel, a nation-wide system for ascertainment of new-born twins with concomitant sampling of umbilical cord blood and immediate zygosity testing.
Funding agency:
- Swedish Research Council
Opens a new window at ror.org.
ROR
Award number:
2021-00180_VR
Award title:
The Swedish Twin Registry
Funding information:
We apply for a continuation of the support of the Swedish Twin Registry (STR), a research infrastructure for population based, epidemiological and molecular studies of twins. The purpose of the STR is to enable research about the importance of genetic and environmental factors for health, lifestyle and behavior.The STR facilitates access to data, samples and twin-contacts for de novo data-collection. For more than 60 years, it has been used for research on a large number of diseases, behaviors and health problems. All living Swedish born twins over the age of 9 years have been contacted by the STR and it is thereby the largest twin registry in the world.Nationwide questionnaires, measurements and telephone interviews have been conducted for different birth cohorts since the 1960s. Broad consents and a unified system make it possible to combine data and samples over the sub-studies to address new research questions. Beside self-reported health and exposures, additional critical information is obtained through regular linkages to the national health registers. At present, the STR holds DNA and other biological samples from more than 58 000 twins to be used for new analyses. Genome-wide genotyping is available for the vast majority.The STR is managed by Karolinska Institutet and led by a Steering Group with mandate for periods of 3 years. There is also an advisory National Council with members from several universities that meets two times per year. It provides an academic arena for input and communication regarding strategies impacting the research enabled by the STR in the future. The grant will support the running costs of the new twin contacts, sample and data collections, upholding the secure database and provide access to data for researchers. The national added value consists in the opportunity to manage and develop an already productive infrastructure in directions that benefits a national range of researchers in a cross disciplinary and transparent manner.
Topic and keywords
Topic and keywords
CESSDA topic classification:
Swedish Standard Classification of Research Subjects 2025:
Relations
Relations
Website:
Related resource:
Publications
Publications
Citation:
Anckarsäter H, Lundström S, Kollberg L, Kerekes N, Palm C, Carlström E, Långström N, Magnusson PK, Halldner L, Bölte S, Gillberg C, Gumpert C, Råstam M, Lichtenstein P. The Child and Adolescent Twin Study in Sweden (CATSS).
Twin Res Hum Genet. 2011 Dec;14(6):495-508.
