It's been exactly the same scenario with my close relative, and your experience makes me suspect that my gut feeling is correct. It's been terrible to watch him going through these cycles of depression and suicide attempts, and his loving parents have been going through hell - yet it's his mother who has been insistent on him taking these drugs, because she is a health professional who has been trained in these methods. I have voiced my thoughts on this in a gentle and non-argumentative way on four separate occasions. I know that his mother wants only the best for him and is acting out of love. But sometimes you need to go with your gut.
When my mum was pregnant with me, she had morning sickness and she was prescribed Thalidomide. My grandmother, who had no education as she was employed as a mill worker from age 14 until her marriage, said to my mum, "Never take any medication during pregnancy". So my mum stopped taking the Thalidomide after a week. Apparently when I was born I had "funny feet" and had to wear built-up shoes for a few months, but that was all. Sometimes the official health advice is simply wrong.