For decades, most people have heard that depression is caused by a “chemical imbalance,” specifically low serotonin levels in the brain. But digging into the deeper layers behind this popular theory, it becomes clear that this narrative may not hold up to the scrutiny it deserves. Alternative voices have long pointed out that the origins of this idea are less scientific fact and more a product of clever marketing and propaganda—helped along by powerful interests in the pharmaceutical industry and echoed by the mainstream media. Even today, the evidence tying depression directly to low serotonin is far from conclusive, and some have argued that the persistence of this story is due less to robust research than to its usefulness in selling certain medications and shaping public perception. To get a clearer picture of how this myth took hold and why so many still believe it, you’ll want to listen to the full episodes where these controversial and thought-provoking viewpoints are explored in depth.