CATSS15 - The Child and Adolescent Twin Study in Sweden (15 years)
CATSS overview:
The Child and Adolescent Twin Study in Sweden (CATSS) is an ongoing longitudinal twin study targeting all twins born in Sweden since July 1, 1992. Since 2004, parents of twins are interviewed regarding the children's somatic and mental health and social environment in connection with their 9th birthday (CATSS-9). At age 15 (CATSS15) and 18 (CATSS18), twins and parents complete questionnaires that, in addition to assessments of somatic and mental health, include 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.
CATSS15:
CATSS15 started in 2010. The study includes all 15-year-old twins and their parents, regardless of whether they participated in CATSS9 or not. The response rate for the twin survey is 52% and for the parent survey it is 48%. The sample consists of 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) in CATSS15 is currently 24,800 out of 42,500 invited (December 2025). The combined response rate is currently 58%. Participants who have not already provided a DNA sample via saliva are requested to do so again. The saliva sample is used for zygosity determination and genotyping. The number of genotyped twins in CATSS15 is currently 15,500 (December 2025).
The question areas in the CATSS15 surveys are listed below. For detailed information about variables, visit strdata.se
Question areas in parent survey:
Administrative Information
AUDIT - Alcohol Use Disorders Identification Test
CMRS - Child Mania Rating Scale
CMO - Child Monitoring
DUDIT - Drug Use Disorders Identification Test
LSC-R - Life Stressor Checklist- Revised
PCR - Parent Child Relationship
PPCP - Parents' Perception of Child's Peers
PLE - Psychotic-like Experiences
Somatic diseases
Spare time activites
SDQ - Strength and Difficulties Questionnaire
Question areas in twin survey:
CMRS - Child Mania Rating Scale
DCQ - Dysmorphic Concerns Questionnaire
EDI-2 - Eating Disorder Inventory - 2
HRS-I - Hoarding Rating Scale-Interview
Physical acitivity
PMS
PLE - Psychotic-like Experiences
Quality of Friendship
RPQ - Reactive and Proactive Aggression Questionnaire
OBVQ - Revised Olweus Bully/Victim Questionnaire
SRD - Self-Reported Delinquency
Self-Reported Alcohol and Drug Use
Sexuality
Somatic diseases
SDQ - Strength and Difficulties Questionnaire
TCI - Temperament and Character Inventory
Tics
Weight and 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
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:
15-year old twins born in Sweden on or after 1st January, 1994
Study design:
- Cohort study
- Observational study
Description of study design:
Data collection was conducted through a paper questionnaire during the first two years. After that the collection was conducted online through a web survey. Until 2020 paricipants still had the possibility to choose a paper survey if they wished. Participation in the study is based on informed consent.
Sampling procedure:
Description of sampling:
All 15-year-old twins born in Sweden on or after 1994, according to the Medical Birth Registry (the National Board of Health and Welfare) and living in Sweden at the time of study invitation. Twins who have declined further participation in the twin registry, have protected identity, have emigrated, or died are excluded. Only complete twin pairs are invited to participate. Data from whole twin pairs and single twins are collected.
Time period(s) investigated:
Number of individuals/objects:
24800
Response rate/participation rate:
58%
Description of the response rate/participation rate:
The total number of participating twins (through the participation of twin and/or parent) is 24,800 out of 42,500 invited (December 2025), resulting in a response rate of 58%.
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:
2010-03 - 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:
SDQ
Type:
Structured questionnaire
Description of the instrument:
Strengths and Difficulties Questionnaire (SDQ) is an assessment method used to measure the mental health of children and young people. The form is based on experiences from two other established and internationally widespread instruments ,the Rutter questionnaire and the Child Behavior Checklist (CBCL).
DOI: 10.1111/j.1469-7610.1997.tb01545.x
Name:
RPQ
Type:
Structured questionnaire
Description of the instrument:
The Reactive-Proactive Aggression Scale (RPQ) is a self-report measure of two main forms of aggression – proactive and reactive
DOI:10.1002/ab.20115.
Name:
DCQ
Type:
Structured questionnaire
Description of the instrument:
Dysmorphic Concerns Questionnaire (DCQ) is a self-report measure with seven items which ask about cognitive and behavioural aspects of dysmorphic concern. It has been validated as a screening tool for body dysmorphic disorder.
DOI: 10.3109/00048679809062719
DOI: 10.1046/j.1440-1614.2001.00860.x
DOI: 10.3109/00048671003596055
Name:
EDI-2
Type:
Structured questionnaire
Description of the instrument:
The Eating Disorder Inventory (EDI) is a self-report questionnaire used 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 that assesses 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) 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 personality 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:
OBVQ
Type:
Structured questionnaire
Description of the instrument:
Revised Olweus Bully/Victim Questionnaire (Perpetrator + Victim, OBVQ-R) is a self-report questionnaire with 42 items, which has been used in different countries, and has adequate psychometric properties to assess the prevalence of victimization and aggression and various forms of bullying worldwide. This version uses 24 of the items.
DOI:10.1007/BF02195509
DOI:10.1348/000709905X53499
Name:
HRSI
Type:
Structured questionnaire
Description of the instrument:
Hoarding Rating Scale-Interview (HRS-I) is a five-item semi-structured interview that assesses 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 Organization (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 for drug-related problems, giving information on the level of drug intake and selected criteria for substance abuse/harmful use and dependence according to the ICD-10 and DSM-4 diagnostic systems. The questions are asked in the parent survey and addresses the parent's drug consumption.
DOI: 10.1159/000081413
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:
2009/739-31/5
Ethical review information:
Ethics application approved on 28th of May 2009
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.
