Treatment-Resistant Depression, Hippocampus Atrophy and Serotonin Genetic Polymorphism

Individuals who are defined as having treatment-resistant major depression (failure of at least 2 trials of an antidepressant at an adequate dose) and currently meet DSM-IV criteria for depression qualify for this study. At the initial visit, each subject is given an MRI in order to perform a volumetric analysis of their hippocampus and a blood sample is taken in order to determine their genotype for the 5-HT1a(serotonin) promoter. Each patient is then aggressively treated (open label) for depression with the goal of remission. A second MRI scan is completed 6 months after sustained remission or 12 months from baseline if remission is not met or sustained. The investigators will select healthy volunteer controls with no personal or first relative history of depression and match with the subjects based on age and handedness. Genotyping and and MRI scan will be performed on the healthy subjects in order to compare all parameters. Hypothesis: It is anticipated that the hippocampal volume will be smaller than those of matched controls. It is also anticipated that the Homozygous G(-1019) genotype will be more prevalent in the patient group than in the healthy subjects. In addition, it is hypothesized that the investigators should find a small increase in hippocampal volume after long-term treatment. Also, most non-responders will be of homozygous G(-1019) 5-HT1a genotype and will have the greatest degree of hippocampal atrophy. Moreover, it is hypothesized that patients carrying a long allele of 5-HTTLPR polymorphism for 5-HTT might show a better response to antidepressants in general. Finally, it is anticipated that the TPH\*A variant of the gene coding for tryptophan hydroxylase will be associated with poorer outcome.