Florida State University issued the following news release:

Media Perpetuates Unsubstantiated Chemical Imbalance Theory of Depression

The theory that depression is caused by a chemical imbalance is often
presented in the media as fact even though there is little scientific
evidence to support it, according to a new study co-authored by a
Florida State University visiting lecturer.

Jeffrey Lacasse, an FSU doctoral candidate and visiting lecturer in the
College of Social Work, and Jonathan Leo, a neuroanatomy professor at
Lincoln Memorial University in Tennessee, found that reporters who
included statements in news articles about depression being caused by a
chemical imbalance, or a lack of serotonin in the brain, were unable to
provide scientific evidence to support those statements.