My wife is taking anti-depressant since last 3 months, it is working fine on her but she is experiencing severe hair fall. is this co-related ?

Hair loss: Although rare hair loss can be possible. Rule out other causes too. Depression it self can cause hair loss.

Maybe.: In my experience, hair loss does not occur with antidepressants. If your wife is better on the antidepressants, but is also experiencing significant hair loss, i strongly recommend discussing this with her treating physician. There could be an unrelated general medical illness involved, such as anemia or low thyroid. If not then perhaps switching to a different antidepressant would help.

Could be: There are many antidepressants I do not know which one she is on. If she is on Lamictal fordepression and that can definitely cause hair loss. Most of the standard antidepressants however do not cause hair loss. If problem persists, it is possible that hypothyroidism is the cause of both her hair loss and her depression. Have her doctor draw a thyroid panel. Otherwise, i would recommend a dermatology consult.