Background
Methods
Aim 1. Recruitment of MZ twins discordant for OCD and creation of a biobank
Participants and recruitment sources
Twin cohort
|
Num. of individual twins as of November 2022
|
Obsessive-compulsive symptom measurement
|
Criteria for selection for potential inclusion
|
---|---|---|---|
CATSS-18
(born 1992-) | 15,400 | Brief Obsessive-Compulsive Scale (BOCS) [13], 17 items
| Top 5% scores on the BOCS |
CATSS-24
(born 1992-) | 7,639 | Obsessive-Compulsive Inventory – Revised (OCI-R) [14], 12 items (hoarding and neutralizing scales not included)
Self-reported question: Have you ever been diagnosed with (or suspected that you have) OCD?
| Top 5% scores on the OCI-R or answered yes to the self-reported question |
DOGSS
(born 1993–1995) | 450 | Kiddie - Schedule for Affective Disorders and Schizophrenia for school-aged children, Present and Lifetime Version (K-SADS-PL) [15], obsessive-compulsive disorder categorical diagnosis
| Met diagnostic criteria for obsessive-compulsive disorder on the K-SADS-PL |
YATSS
(born 1985–1992) | 6,870 | OCI-R [14], 12 items (hoarding and neutralizing scales not included)
| Top 5% scores on the OCI-R |
STAGE
(born 1959–1985) | 43,000 | 7-item obsessive-compulsive disorder questionnaire [4] Self-reported question: Have you ever been diagnosed as having an obsessive compulsive disorder? (yes/no) | Top 5% scores on the 7-item obsessive-compulsive disorder questionnaire or answered yes to the self-reported question |
Procedures
STUDY VARIABLE
|
MEASURED BY
|
---|---|
Socio-demographic and clinical information
| |
Demographics | Self-reported questionnaire |
Zygosity | Self-reported questionnaire, confirmed by genotyping of saliva or whole-blood derived DNA using a whole-genome covering SNP array [17] |
Treatment history (medication, therapy) | Clinician-administered interview |
Psychiatric disorders
| |
Structured Clinical Interview for DSM-5 (SCID-5) [18] | Clinician-administered interview |
OCD severity and symptom dimensions
| |
Yale-Brown Obsessive Compulsive Scale (Y-BOCS), Symptom Severity and Checklist [19] | Clinician-administered interview |
Obsessive Compulsive Inventory-Revised (OCI-R) [14] | Self-reported questionnaire |
Cognitive function
| |
Similarities, Vocabulary, Information, Block design, Matrix reasoning, and Visual puzzles from the Wechsler Adult Intelligence Scale-fourth edition (WAIS-IV) [20] | Clinician-administered test |
Reading the mind in the eyes (RTMITE) [21] | Clinician-administered test |
Fragmented Picture Test (FPT) [22] | Clinician-administered test |
Edinburgh Handedness Inventory modified [23] | Self-reported questionnaire |
Biometric data and general health
| |
Height | Physical exam by nurse |
Weight | Physical exam by nurse |
BMI | Physical exam by nurse |
Head circumference | Physical exam by nurse |
Blood pressure | Physical exam by nurse |
Pulse | Physical exam by nurse |
Medical and Clinical Genetic Questionnaire [10] | Self-reported questionnaire |
Biospecimens
| |
Blood | Collected by nurse |
Saliva | Collected by nurse |
Hair | Collected by nurse |
Nails | Collected by nurse |
Urine | Collected by participant |
Stool | Collected by participant |
Brain imaging
| |
High resolution structural scan (T1) | Study coordinator |
Diffusion Tensor Imaging (DTI) | Study coordinator |
Resting state functional Magnetic Resonance Imaging (rsfMRI) | Study coordinator |
Other measures
| |
Adult Self Report (ASR) [24] | Self-reported questionnaire |
Adult Autism Spectrum Quotient (AQ) [25] | Self-reported questionnaire |
Sensory Profile Adolescent/Adult (SP-A) [26] | Self-reported questionnaire |
Swedish Eating Assessment for Autism Spectrum Disorders (SWEAA) [27] | Self-reported questionnaire |
Attention-Deficit/Hyperactivity Disorder Self Report Scale (ASRS) [28] | Self-reported questionnaire |
Camouflaging Autistic Traits Questionnaire (CAT-Q) [29] | Self-reported questionnaire |
Aim 2. Identification of risk factors that are in the causal pathway to OCD
Design rationale
General statistical framework
Register-based data
Register name | Examples of available variables |
---|---|
Swedish national registers
| |
National Patient Register [12] | Information on all inpatient and outpatient contacts at all hospitals and specialist centers. Includes primary and supplementary diagnoses based on the International Classification of Diseases codes, including somatic (e.g., autoimmune diseases, infections, allergies, respiratory diseases) and psychiatric disorders (e.g., trauma and stress related disorders, mood disorders, substance use disorders). |
Medical Birth Register [35] | Information on antenatal, obstetric, and neonatal care, including mother’s parity, mother’s age, type of delivery, obstetric complications (e.g., preeclampsia, gestational diabetes, antepartum or postpartum hemorrhage), gestational age, birth weight, birth order, APGAR scores, neonatal hypoglycemia, neonatal jaundice, neonatal infections, neonatal respiratory distress, congenital malformations, etc. |
Prescription Drug Register [36] | Individual-level data for all prescriptions dispensed for in- and outpatients, including type of medication registered using Anatomical Therapeutic Chemical (ATC) Classification System codes, dosage, prescription date, prescriber, pharmacy, etc. |
Swedish Twin Registry
| |
Variables collected via questionnaires in different waves, including somatic and mental health, personality development, vaccinations, substance use, physical activity or psychosocial adaptation and environment (e.g., traumatic events, school problems, friendships, bullying victimization/perpetration). |