What is a mental illness? To most psychiatrists, the answer lies in the DSM-IV, essentially a catalog of diagnoses and diagnostic features of each disorder. It has been derided as presenting a “cookbook” (or, perhaps less PC, a “Chinese menu”) approach to psychiatry, in which a diagnosis is made on the basis of the presence of a number of symptoms drawn from a list.
While this approach has proven helpful for research and clinical purposes, it unfortunately oversimplifies what is undoubtedly an extraordinarily rich spectrum of mental disorders. (It also, of course, calls into question where is the demarcation between “normal” and “disorder” on that spectrum, but more about that some other time.) As any clinician will tell you, no two depressed patients are alike, just as no two schizophrenics are alike, no two bipolar patients are alike, and so forth.
In reality, there may be dozens of diseases that we now call “scihzophrenia” (or “depression” or “panic disorder,” etc). Some may stem from a clear genetic mutation in some as-yet unidentified gene, while others may be a consequence of endocrine dysregulation or disturbances in brain development. Others may be defined by their propensity to respond (or not) to various pharmaceutical agents, or the patient’s biological tendency to endure side effects of such agents such as weight gain or movement disorders.
The National Institute of Mental health (NIMH) is trying to expand our nosologic system by incorporating neurobiolgoical and physiological measures as well as observable behavior in our classification of psychiatric disorders. The Research Domain Criteria aims to
… define basic dimensions of functioning (such as fear circuitry or working memory) … across multiple levels of analysis, from genes to neural circuits to behaviors, cutting across disorders as traditionally defined.
What might this mean for the future of psychiatry? For starters, instead of a checklist to generate a diagnosis, a clinician might order a brain scan, a blood test, a measure of some genetic marker, or a more intensive review of one’s history in order to develop an “individualized” treatment approach. How long it takes to get to this point (and whether we can afford it) remains to be seen.