08/12/2025
For decades, many have been told that depression stems from a “chemical imbalance” in the brain, particularly a deficiency in serotonin. This idea has shaped mental health messaging, drug marketing, and public understanding for years. But a major new study is now challenging this long-held belief, and the implications are massive.
Researchers at University College London recently published a landmark umbrella review in Molecular Psychiatry, which critically examined decades of research into serotonin and depression. Their conclusion is stark: there is no convincing evidence that low serotonin levels cause depression. In fact, some findings suggest that long-term use of certain antidepressants could actually reduce serotonin activity in the brain.
This is significant because most widely prescribed antidepressants, such as SSRIs (Selective Serotonin Reuptake Inhibitors), are based on the theory that boosting serotonin can relieve depressive symptoms. But if the serotonin deficiency model is unsupported, it raises questions about how these drugs actually work, and whether they are being prescribed on a misleading premise.
Up to 90 percent of the public believes in the chemical imbalance explanation, according to the researchers. This widespread belief may unintentionally narrow people’s understanding of depression, making it seem like a purely biological flaw rather than a complex interplay of emotional, psychological, and social factors. It may also discourage patients from exploring effective non-drug treatments like psychotherapy, lifestyle interventions, trauma-informed care, and building strong social connections.
Importantly, the study does not suggest that antidepressants never help. Many people report improvements while using them, and mental health is deeply personal. But it does encourage a more nuanced view of what causes depression, urging clinicians and the public to move beyond overly simplistic biological explanations.
Mental health is complex. It is affected by relationships, environment, stress, and past experiences. Recognizing this complexity opens the door to more holistic, compassionate, and effective approaches to care.
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