The Chemical Imbalance Hypothesis: An Evaluation of the Evidence

Powered by philosophic argument, scientific evidence, and multibillion dollar pharmaceutical companies sponsoring multimillion dollar advertising campaigns, the chemical imbalance hypothesis has saturated our academic and popular culture. This saturation is, at least partially, responsible for the more than 10 billion dollars annually spent on antidepressant medication in the United States. But what is the “chemical imbalance” hypothesis? And what evidence supports it? This article will provide an account of the chemical imbalance hypothesis, a history of its development, and the evidence provided for its justification. This article will show that the evidence for the chemical imbalance hypothesis is unconvincing. It will discuss why, despite the unconvincing evidence, the hypothesis lingers. And, finally, it will suggest an alternative approach to mental illness that avoids some of the pitfalls of a biological reductionistic account of mind.