Objective: Variation in the serotonin transporter gene (SLC6A4) promoter region has been shown to influence depression in persons who have been exposed to a number of stressful life events.
Method: We evaluated whether genetic variation in 5-HTTLPR, influences current depression, lifetime history of depression and quantitative measures of depression in persons with chronic psychotic disorders. This is an association study of a genetic variant with quantitative and categorical definitions of depression conducted in the southwest US, Mexico and Costa Rica. We analyzed 260 subjects with a history of psychosis, from a sample of 129 families.
Results: We found that persons carrying at least one short allele had a statistically significant increased lifetime risk for depressive syndromes (P < 0.02, odds ratio 2.18, 95% CI 1.10-4.20).
Conclusion: The 'ss' or 'sl' genotype at the 5-HTTLPR promoter polymorphic locus increases the risk of psychotic individuals to develop major depression during the course of their illness.