How long has your friend started the medicine? It takes time for the medicine to be effective in balancing the endorphine inside the brain. Advise him/her to discuss the problem with the doctor. The doctor need to adjust the medicine according to individual response to the medicine. Some depression patients have suicidal ideas. It is important for them to use medicine for stablizing their mood first. Don't just ask them to think positively because they would think that nobody understand them. It is really a disease!!!