Serotonin transporter gene × environment and risk of depression in community-treated epilepsy

This study aimed to test whether a specific serotonin transporter (5HTT) gene polymorphism interacting with life stress increased the risk of depression in patients with epilepsy.

The Tasmanian Epilepsy Register Mood Study (TERMS) used a cross-sectional study design of a community sample of patients with epilepsy previously recruited into the Tasmanian Epilepsy Register. It employed a mailed self-complete questionnaire and saliva DNA collection. Depression was assessed using the Center for Epidemiologic Studies Depression Scale. Environmental measures were selected to cover recent stressful events, epilepsy-related stress, current social support, and early life stress.

Of 820 eligible participants, 553 (67%) participants completed the study. Experience of at least one stressful life event was very common, with a significant association between depression and the stressful life events (F=26.2, df=3, p<0.001). There was no association between serotonin transporter genotype and level of depressive symptoms reported (F=0.421, df=2, p=0.7). There was no evidence of any adverse life experiences interacting with serotonin transporter genotype to moderate the risk of depression.

The failure to demonstrate a main effect of genotype on depression or a gene × environment interaction differs from several studies of patients with other chronic diseases. However, it is consistent with larger general population studies.