How come antidepressants cause mania in bipolar patients?

They increase mood: Typically, antidepressants cause an increase in mood and energy because a common symptom of depression is fatigue, sleeping too much, feeling tired all the time and lacking energy. The problem is that the boost in mood from the anti-depressant can then lead to manic episode in bipolar disorder--which is being very, very high in mood and energy. Hope this helps.

Bipolar Disorder is: a cyclic disorder with repeated periods of mania, hypomania & depression. An antidepressant can be stimulating to the point that it flips a person into mania.