You wouldn’t be alone in hearing that you have a chemical imbalance or serotonin deficiency (“low serotonin”). But did you know that there is no convincing evidence to support the idea that depression or anxiety is caused by such a thing? The chemical imbalance theory has been widely communicated by the drug industry; however, there was never proof of it.* **
Depression being caused by “low serotonin” or “serotonin deficiency,” also referred to as “the chemical imbalance” theory of depression, was an idea conceived in the 1960s. It was amplified by drug companies in the 1990s and 2000s because it helped promote their products (which act on serotonin). Psychiatrists widely dismiss the chemical imbalance theory today.* **
There is still much doctors do not understand about mental health conditions such as depression and anxiety. It is more widely believed that these conditions occur largely due to your family background, life events, and relationships, and other biopsychosocial factors.
** Moncrieff, J., Cooper, R.E., Stockmann, T. et al. The serotonin theory of depression: a systematic umbrella review of the evidence. Mol Psychiatry (2022). https://www.nature.com/articles/s41380-022-01661-0