Well I think that we do not know enough about genesis of depression and other mental issues. So this is just symptomatic therapy. And as such it should be prescribed only for very short terms. Analogy: how would you perceive someone who prescribed his febrile patient paracetamol for 10 years just because it works? And in his defense he/she claims that febrile condition has well known metabolic chain and that paracetamol lowers fever mainly by interrupting the COX → PGE₂ part of the fever pathway in the brain.