Polygenic risk indices for schizophrenia, bipolar and major depressive disorder associated with addiction (smoking and alcohol) in the Russian population in patients with schizophrenia or schizophrenia spectrum disorder

Methods

The sample consisted of 887 patients diagnosed with schizophrenia or schizophrenia spectrum disorders. Information on smoking and alcohol use was obtained from patient records and interviews. The polygenic risk score for schizophrenia SZ-PRS (Trubetskoy V. et al., 2022), bipolar BPD-PRS (Adams, James M. et al., 2025) and major depressive disorder MDD-PRS (Nemani A. et al., 2025) was used as an indicator of genetic predisposition, calculated as a weighted sum of single nucleotide polymorphisms that were associated with mental disorders in a genome-wide association study. For statistical processing of the data, a logistic regression model with stepwise algorithms for inclusion and exclusion of predictors was used. Student’s t-test was used to test the equality of the means in the two samples (gender-dependence, PRS-dependence).