Treatment-Resistant Depression, Hippocampus Atrophy and Serotonin Genetic Polymorphism

Reduction of volume of the hippocampus has been associated with major depression in many studies. It has been suggested that antidepressants may protect against hippocampus volume loss in humans associated with multiple episodes of depression and may also reverse the reduction of volume caused by the depression. In addition, genetic markers for serotonin are implicated with depression, and may be an indication of reduced response to antidepressant treatments. This study aims to enroll patients who are defined as having treatment resistant depression (no remission after at least 2 treatments trials with an antidepressant). They will receive an MRI scan at the initial visit and either 6 months after sustained remission or 12 months after they enter the study for non-remitters. They will also be asked to give a blood sample for genotyping. They will be matched by age and handedness to healthy volunteers with no personal history of depression who will also receive an MRI scan and genotyping. The first aim is to compare hippocampal volume of depressed subjects to healthy controls. It is anticipated that subjects will initially have smaller hippocampal volume but of those who sustain remission, there will be a small increase in hippocampal volume. It is also anticipated that specific genetic markers will be related to individuals response to antidepressant treatments.