Effects of Bupropion in Depression

Bupropion MR will be given open label to all participants in the depression group. Participants will receive 150mg od for one week. The dose will then be increased to 150mg bd for the following 5 weeks. Participants in the control group will recieve no drug. Note that the study is not assessing the safety or efficacy of buprion-- it is using bupropion to assess the neural effects of altering central dopaminergic function in depressed patients.