If the only way people with bipolar ever are happy is when they are manic, why give lithium?

I don't: There are two reasons to give medications in bipolar patients. One is to alleviate current symptoms and the second is to diminish the risk of symptoms worsening over time. Untreated patients with bipolar disorder tend to experience progressive worsening of the severity of their depression over time. The only medications fda approved for the depression symptoms are lamictal, seroquel XR and symbyax (fluoxetine and olanzapine).