Psychopharmacology: a house divided.

Background: Psychopharmacology and psychiatry during the past 50 years have focused on the specificity model in which it is assumed that psychiatric disorders are specific entities which should respond to drugs with specific mechanisms of action. However, the validity of this model has been challenged by the approval of multiple drugs for the same disorder, as well as the approval of single agents for a variety of disorders which have little in common. As an example of this unacknowledged paradigm shift, I will examine the foundation for using antipsychotics in the treatment of depression.

Methods: An extensive literature search of studies investigating various mechanisms of actions of antipsychotics and antidepressants with the goal of identifying neurochemical processes common to both.

Results: The neurochemical differences in these classes of drugs appear to be profound, although several processes are common in both, including some degree of neuroprotection and changes in the epigenome. Whether these common features have any effect on clinical outcome remains in doubt.

Conclusions: While psychopharmacology and psychiatry remain largely committed to the specificity model, it appears that clinicians are prescribing on a dimensional model wherein symptoms are being treated with a variety of drugs, regardless of the diagnosis.