Testing bidirectional relationships between alcohol use and depressive symptoms: What is the role of the serotonin transporter gene?

Alcohol abuse often co-exists with a major depressive disorder. In order to understand the development of this comorbidity, it is important to concentrate on the preceding process. It has been suggested that the link between alcohol use and depressive symptoms is a result of an interaction with genetic factors. The aim of this study was to longitudinally examine the effect of the 5-HTTLPR genotype on the association between depressive symptoms and alcohol use in a Dutch community sample. Following a stepwise approach, bivariate correlations, longitudinal regression analyses, and latent growth curve analyses were separately conducted for 316 males and 321 females. A positive correlation between depressive symptoms and alcohol use was shown in female carriers of the 5-HTTLPR short allele. In addition, latent growth curve analyses showed a positive association between alcohol use and the intercept of depressive symptoms (but not the slope), but only in female carriers of the 5-HTTLPR short allele. These findings show that alcohol use may be positively related, at least cross-sectionally, to depressive symptoms in female carriers of the 5-HTTLPR S allele, and indicate that moderators such as SLC6A4 genotype and sex need to be taken into account when examining associations between depressive symptoms and drinking behavior. In order to gain insight into the longitudinal association between alcohol use and depressive symptoms, studies should concentrate on earlier stages and focus on more fine-grained research designs that allow day-to-day changes in both alcohol use and depressive symptoms.