The genetic contribution to individual differences in drug response is probably polygenetic with a number of susceptibility genes and gene interactions. The non-genetic factors are likewise comprehensive, interacting and might even be under genetic influence themselves. Thus, antidepressant response is a complex and multifactorial phenomenon.

This study sought to examine the effects of various genetic variations on the outcome of antidepressant treatment taking into account the possible interactions with environment and personality.

Patients discharged from a psychiatric clinic in a region of Denmark with the diagnosis of single depressive episode are identified via the Danish Psychiatric Central Research Register and invited to participate in interviews regarding present psychiatric illness, treatment response, recent life events, and personality disorder. Further, blood test for genetic analyses are taken and the participants complete questionnaires regarding present symptoms, personality traits, coping, and side effects.

The study will include approximately 400 patients.

Data collection will proceed until January 2008, and the presentation will therefore include new and unpublished results.

Associations between genetic polymorphisms (including the genes encoding the serotonin transporter, catecol-O-methyl-transferase, 5-HT2 receptors, dopamin beta-hydroxylase, cytochrome P450 and brain derived growth factor) and outcome of antidepressant treatment will be presented.

The systematic recruitment of a relatively large, unselected and ethnic as well as phenotypic homogeneous sample of patients and the inclusion of genetic as well as non-genetic predictors of treatment response will make it possible throw new light on the role of genetic variation in the treatment of depression.