We would agree that many brain processes, including the serotonin system likely play a complex, though poorly understood, role in emotion and behaviour, including depression. Yet such ideas are different from the specific claim that depression is caused by low serotonin levels or serotonin activity (often communicated to patients) that our review specifically examines.
Psychiatrists will continue to find it difficult to give up the serotonin theory of depression because they believe antidepressants are effective. As nearly all antidepressants have an effect on serotonin, as far as they are concerned, this mechanism must be how they work. Questioning whether antidepressants are any better than placebo creates grave concern for the professional viability of psychiatrists, as does debunking the serotonin theory of depression. Psychiatrists need to give up such a vulnerable basis for their practice.