The question of what constitutes a mental disorder is a hot issue right now because the Diagnostic and Statistical Manual of Mental Disorders is in the process of making a major revision, from IV-R to V. In that regard, the authors are considering some significant changes to the definition of mental disorder. The definition is a crucial issue for mental health professionals and society in general for many different reasons, including who has access to care and how we think about the nature of the human condition. Given the complex nature of the issues and the fragmentation and conceptual confusion in psychology (and, yes, psychiatry), it should not come as a surprise that there is much confusion and controversy regarding what exactly constitutes a mental disorder. (See, for example, this article by Gary Greenberg).
Here are some basic questions regarding the definition of a mental disorder:
Where is the line between normal variation and pathology? Are mental disorders categorically different or are do they simply exist at the extremes of a continuum?
Does having a mental disorder say anything about one's character or should it be completely separated from that, and thus the individual should not be judged or stigmatized? What if the disorder is a personality disorder? Doesn't that, by definition, say the structure of a person's character is a problem?
Are mental disorders natural kinds that can be objectively specified or are they entirely the result of social values and the cultural construction of what is normal (i.e., different values will lead to different conceptions of what is a mental disorder)?
Are mental disorders essentially like other diseases in medicine or are they a fundamentally different kind of condition?
This last question is particularly important from the vantage point of psychiatry relative to other mental health professions. Psychiatrists are, of course, medical doctors, and there is thus much pressure for psychiatry to perceive mental disorders as akin to other medical conditions. And it is the American Psychiatric Association that produces the DSM. Yet many mental health professionals, like professional psychologists, counselors, social workers, and marriage and family therapists are neither trained in medicine nor inclined to want to reduce the problems they see to dysfunctional biology.
If you wonder whether this issue has real consequences, check out an open letter about the upcoming DSM revisions from the Division of Humanistic Psychology. The essence of the letter is the concern about medicalizing human problems and suffering and framing the nature of mental disorders in a biologically reductionistic way. (By the way, I signed the petition).
One of my earliest articles (here in word form finalHD) grounded in the UT was on the question of what is a mental disorder and focused especially on the issue of whether mental disorders were of the same essential kind as other biological diseases. My answer was that some mental disorders are likely reducible to (neuro) biological dysfunction that produces harmful consequences. Consider, for example, a rather obvious case like Alzheimer's disease. The symptoms of disorientation, forgetfulness and poor judgment are almost certainly reducible to neurological malfunctions (e.g., tangles and plaques in the hippocampus). Other highly likely candidates for what I call mental diseases are autism, schizophrenia, severe cases of OCD, Bipolar 1. Why are these conditions probably mental diseases? Because the patterns of psychological behavior are functionally unusual and difficult to explain via general psychological theory. A more parsimonious explanation is that there likely is malfunctioning processes at the level of neurobiology.
On the flip side, there are many mental disorders that cannot be reduced to or understood in terms of biological malfunction. Instead, these conditions are maladaptive psychological patterns (often of a cyclical nature) that result in elevated (AKA clinically significant) levels of distress and dysfunction for the individual and/or society. Consider the following example:
Tina is an 18-year-old freshman. She grew up in a small, rural town and is a first generation college student with hopes of being a physician. She did extremely well in high school and has always been very driven and conscientious. However, her first semester of college did not go very well. She experienced difficulty making friends, and she was uncomfortable with the drinking and party atmosphere. She focused a lot on her studies and studied several hours a day, but she struggled to get the As she expected (her first semester grades were a 3.2). Now she is reporting problems taking tests and staying focused and is worried that she has ADD. She is starting to have trouble sleeping, as she can't fall asleep because she is constantly worrying about what she needs to do the next day. She is also having nightmares about failing out of school. She also is reporting frequent stomach aches, and she is now considering whether she should transfer to a college that is closer to home.
This narrative depicts an emerging maladaptive psychological pattern and a clinician should wonder about an anxiety, depressive, or adjustment disorder diagnosis. But her symptoms are completely comprehendible via normal psychological processes, and there is no reason to assume or presuppose any sort of biological dysfunction. (This is not to say that medication could not or should not be prescribed, only that the explanation for Tina's problems would be at the psychological level rather than the biological level).
The idea that there are mental disorders that are not bio-medical conditions might make some biomedical psychiatrists experience cognitive dissonance, but professional psychologists should embrace the idea.