This is something that has been debated for many years, and has its origins in the efforts to reduce the stigma associated with mental illness. In the 1960s, it was thought that if depression could be characterised as a medical problem, then it could be treated medically by the prescription of the new anti-depressant medications. While this initiative was fairly successful in terms of reducing stigma, there was little to no research supporting the idea that depression was caused by a chemical imbalance in the brain.

This lack of support has been demonstrated by a lot of research over the years, and it is now clear that the ‘chemical imbalance theory’ should be abandoned.

If you’re interested in some of the latest findings, you can read more in this article in The Conversation.