Exploring the implications of case selection methods for psychiatric molecular genetic studies

Area of Science:

• Psychiatry
• Genetics
• Epidemiology

Background:

• Molecular genetic studies rely on precise proband selection.
• Empirical guidance for sampling strategies in psychiatric genetics is limited.
• Understanding genetic risk requires accounting for complex diagnostic relationships.

Purpose of the Study:

• To examine the impact of proband selection decisions on genetic risk profiles.
• To provide empirical data for optimizing sampling strategies in psychiatric genetic research.
• To assess the effects of censoring comorbid diagnoses and using secondary ascertainment.

Main Methods:

• Utilized a large Swedish population cohort (1940-2003) with diagnoses of major depression (MD), anxiety disorders (AD), alcohol use disorder (AUD), drug use disorder (DUD), bipolar disorder (BD), and schizophrenia (SZ).
• Assessed genetic risks using validated family genetic risk scores.
• Analyzed the implications of censoring comorbid cases and employing secondary ascertainment.

Main Results:

• Censoring anxiety disorder cases in a major depression cohort broadly reduced genetic risk for multiple disorders.
• Excluding schizophrenia cases had a smaller, focal impact on major depression genetic risk.
• Screening for preceding alcohol or drug use disorders did not increase genetic risk in selected cohorts.
• Secondary ascertainment can increase genetic risk, but closely related disorders show a moderate, generalized elevation.

Conclusions:

• Proband selection significantly influences genetic risk profiles in psychiatric research.
• Caution is advised when excluding comorbid diagnoses or using secondary ascertainment.
• Findings offer guidelines for optimizing sampling strategies in genetic studies of major depression, anxiety disorders, substance use disorders, bipolar disorder, and schizophrenia.