If you or your friend feel depressed, e.g. you don't care about hygiene, you are no more interested in anything, eat less, don't go out, don't want sex, have suicidal thoughts or even actions, this requires treatment. You should understand that all unpleasant conditions like depression, fears or anxiety have chemical roots. They are caused by imbalance of certain chemicals in our brain and can be treated with anti-depressants. It is advisable to choose antidepressant together with your doctor.