Objective: The short allele of a functional polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been shown to interact with stressful life events to predict depression in otherwise healthy individuals. Whether the short allele increases risk for depression associated with the stress of a chronic illness has not been established.
Method: In a cross-sectional genetic association study, the authors examined the association of 5-HTTLPR with current depression (measured by the Computerized Diagnostic Interview Schedule), perceived stress (measured by the Perceived Stress Scale), and 24-hour urinary norepinephrine excretion in 557 outpatients with chronic coronary disease.
Results: Among individuals carrying an s allele, 25% (97 of 383) had current depression, compared with 17% (29 of 174) of l/l homozygotes. The unadjusted odds ratio was 1.6, with a 95% confidence interval (CI) of 1.0-2.6; the age- and gender-adjusted odds ratio was also 1.6 (95% CI=1.0-2.5). Participants carrying an s allele had a higher mean score for perceived stress than l/l homozygotes (5.4 versus 4.7) and a higher rate of moderate or high perceived stress (adjusted odds ratio=1.6, 95% CI=1.1-2.3). Mean 24-hour norepinephrine excretion was higher in s allele carriers (55.6 versus 50.2 mg/day), who were more likely to have norepinephrine values in the highest quartile (adjusted odds ratio=1.7, 95% CI=1.0-3.0).
Conclusions: Among patients with chronic illness, carriers of the s allele of 5-HTTLPR are more vulnerable to depression, perceived stress, and high norepinephrine secretion. These factors may contribute to worse cardiovascular outcomes in these patients.