Finnish adoptive family study: sample selection and adoptee DSM-III-R diagnoses

Area of Science:

• Psychiatry
• Genetics
• Epidemiology

Background:

• Schizophrenia is a complex psychiatric disorder with suspected genetic and environmental influences.
• Adoption studies are valuable for disentangling genetic from environmental factors in disease etiology.

Purpose of the Study:

• To investigate the genetic heritability of schizophrenia using a robust adoption design.
• To differentiate genetic contributions from environmental influences in the development of schizophrenia.

Main Methods:

• A nationwide sample of adoptees born to mothers with schizophrenia (index group) and control mothers was utilized.
• Diagnostic interviews and record reviews were conducted using DSM-III-R criteria for mothers and adoptees, with blind assessments.

Main Results:

• The prevalence of schizophrenia was significantly higher in index adoptees (6.7%) compared to control adoptees (2.0%).
• Including broader spectrum disorders like schizoaffective and schizophreniform disorders further amplified the diagnostic contrast between groups.

Conclusions:

• The study decisively confirms a significant genetic liability for typical schizophrenia.
• This genetic predisposition appears to extend to a wider range of psychotic and non-psychotic disorders, suggesting a broad genetic spectrum.