Obsessive-compulsive disorder as a risk factor for schizophrenia: a nationwide study

Area of Science:

• Psychiatry
• Genetics
• Epidemiology

Background:

• Obsessive-compulsive disorder (OCD) and schizophrenia frequently co-occur, yet their clinical and etiological relationship remains poorly understood.
• Investigating shared etiological factors between OCD and schizophrenia can inform clinical practice, research, and patient understanding.

Purpose of the Study:

• To determine if patients diagnosed with OCD have an increased risk of developing schizophrenia and schizophrenia spectrum disorders.
• To assess whether a family history of OCD is a risk factor for schizophrenia and schizophrenia spectrum disorders.

Main Methods:

• A prospective cohort study utilizing longitudinal nationwide Danish registers, encompassing 45 million person-years of follow-up.
• Inclusion of 3 million individuals born between 1955 and 2006, followed from 1995 to 2012.
• Survival analyses adjusted for demographic factors, assessing the risk of schizophrenia spectrum disorders following an OCD diagnosis or family history of OCD.

Main Results:

• A prior OCD diagnosis was associated with a significantly increased risk of schizophrenia (IRR=6.90) and schizophrenia spectrum disorders (IRR=5.77).
• Offspring of parents with OCD showed an elevated risk for schizophrenia (IRR=4.31) and schizophrenia spectrum disorders (IRR=3.10).
• These associations remained statistically significant after controlling for family history of other psychiatric disorders and individual psychiatric history.

Conclusions:

• A diagnosis of OCD is linked to substantially higher rates of schizophrenia and schizophrenia spectrum disorders.
• The findings suggest that OCD, schizophrenia, and schizophrenia spectrum disorders may share common underlying etiological pathways.
• This research highlights a potential shared genetic or environmental basis contributing to both conditions.