In June of 2005 Tom Cruise shook the world with his statements about "chemical imbalance" on the Today Show with Matt Laurer. Since that time Florida researchers have investigated the pharmaceutical / psychiatric claims of "chemical imbalance" and recently a study was released which you can find here: http://www.springerlink.com/content/u37j12152n826q60/fulltext.pdf entitled "The Media and the Chemical Imbalance Theory of Depression"
The researchers examined media reports referring to this chemical imbalance theory and asked reporters for evidence supporting their claims. Responses were received from multiple sources, including practicing psychiatrists, clients, and a major pharmaceutical company. The evidence offered was not compelling, and some sources flatly stated the proposed theory of imbalance was known to be incorrect.
VIDEO: These Florida researchers discuss their earlier findings of "chemical imbalance" on Tampa Bay's Fox 13, Kathy Fountain show: