 This study is being done to look at how well people respond to two very different drug treatments for depression. Clinically, people with depression can respond differently to drug treatments for reasons which are not always clear. Some of our own recent research suggests that people with depression who have a family history of bipolar disorder or completed suicide, may react differently to standard antidepressant medications than those without such a family history. Our data shows that family history of completed suicide, as well as the known predictor of family history of bipolar disorder, may help identify a pre-bipolar high risk group i.e. they currently have depression but at some future date will declare a bipolar illness manic-depression by virtue of development of a manic episode also. Our research suggests that treatment- emergent symptoms in response to a trial of antidepressant, such as agitation may be strong predictors of future bipolarity and inherently dangerous particularly as they are not ascribed to the antidepressant treatment. Finally, it is possible that this subgroup of those with depressive illness may respond better and more safely to lithium, a mood stabiliser used in known bipolar depression. 