A multivariate twin study of obsessive-compulsive symptom dimensions

Area of Science:

• Psychiatry
• Behavioral Genetics
• Clinical Psychology

Background:

• Obsessive-compulsive disorder (OCD) presents with significant clinical heterogeneity.
• The underlying etiologic mechanisms contributing to this heterogeneity remain unclear.

Purpose of the Study:

• To investigate the structure of genetic and environmental risk factors across major OCD symptom dimensions.
• To clarify the etiology of OCD heterogeneity.

Main Methods:

• Utilized self-report questionnaires from 4355 female twins in the TwinsUK registry.
• Applied multivariate twin model fitting to analyze scores on the Obsessive-Compulsive Inventory-Revised and its subscales.

Main Results:

• An independent pathway model best explained the data, indicating both shared and unique genetic/environmental factors influence OCD dimensions.
• The hoarding dimension exhibited the lowest loading on common factors and was predominantly influenced by specific genetic effects (54.5%).
• Most genetic variance for other dimensions stemmed from shared factors, while nonshared environmental variance was largely dimension-specific.

Conclusions:

• OCD is unlikely to be etiologically homogeneous, with significant overlap but also distinct genetic and environmental influences.
• Dimension-specific factors, particularly nonshared environmental influences, play a crucial role in OCD symptom expression.
• Hoarding appears to have the least genetic overlap with other OCD symptom dimensions, with implications for diagnostic classification (e.g., DSM-5).