Given my recent post on changes to the way a number of mental disorders are defined, I thought it might be useful to be a good scientist and give you an operationally definition of “mental disorder.” This three-part series is excerpted from a textbook on abnormal psychology that I am currently writing, as well as being hosted on my free, online Abnormal Psychology: An e-text.
Below, we will examine a number of different ways that researchers have attempted to identify normal from abnormal behaviors.
The terms “mental disorder,” “mental illness,” and “psychopathology” are often used interchangeably by those in psychology and related fields; all refer to the study of unusual or abnormal behaviors. Unlike terms and concepts in many of the physical sciences, however, there is not a single, agreed-upon by all operational definition for these terms. The primary definitional conflict hinges on this question: Can mental disorders be defined as a scientific term, or are they instead socially constructed?
This lack of a single definition can lead to confusion and communication problems both when mental health professionals, such as psychologists, psychiatrists, counselors, or social workers, attempt to talk to each other and to the general public. As a result, mental disorders are used and defined in a variety of ways. Below are descriptions of the most common perspectives.
Mentals Disorders as Statistical Deviance
The statistical deviance perspective has enormous common sense appeal, as it involves defining abnormal behavior by comparing an individual’s behavior to the frequency of occurrence of the same behavior in the general population. A behavior is considered abnormal if it occurs rarely or infrequently in the general population. This definition lends itself very well to measurement, as researchers and clinicians can administer objective assessments to clients and get accurate measurements of just how far their depression, anxiety, hyperactivity, and so on are from the norm. As such, this definition is often seen as highly scientific.
Unfortunately, several problems are apparent when this model is examined closely. First, who determines how far from the norm is too far from the norm? It is not as if there is a stone tablet handed down from the psychopathology gods that has “Behaviors that are two or more standard deviations from the norm shall be considered abnormal” written on it. Instead, researchers and clinicians make that decision. Often, behaviors are considered “abnormal” if they occur in less than 5% of the population (1.645 standard deviations from the mean), but this is an entirely arbitrary cutoff. Another concern is that the tests that measure one’s deviation are developed from within a particular cultural framework. In other words, there is not an objective, scientific definition of “obsessive-compulsive disorder,” there is only the definition that the researchers developing the measure have (and someone else may not agree with it).
It is also worth noting that when viewing behavior, both sides of the normal curve would be considered “abnormal.” So, according to this model, both someone with very high and very low general anxiety would be considered abnormal. In the real world, though, it is usually only one tail of the curve that is viewed as problematic or abnormal. For illustrative purposes, picture someone with an IQ of 70 and another person with an IQ of 130. On a scale where 100 is the average, with a standard deviation of 15, both are equally deviant from “normal” intelligence. Most people, however, would only consider the person with extremely low IQ to have a mental disorder, another problem with this conception.
Mental Disorders as Social Deviance
In the social deviance perspective, behavior is deemed abnormal if it deviates greatly from the accepted social standards, values, and norms of an individual’s culture. This is different from the statistical perspective described above, as this method is uninterested in the actual norms of the population. This is because a population may have accepted standards that the majority of the culture do not actually meet. An example of this would be using alcohol and tobacco prior to the legal age of use, which would be considered unlawful and socially unacceptable, yet major surveys show that over 75% of high school seniors have consumed alcohol.
The problems with the social norms perspective are fairly obvious. First, there is little to no objective validity, due to individuals and groups even within the same culture having different ideas of what is socially acceptable. Second, what is acceptable at one point in time can become unacceptable with the passage of time, or vice versa. Until 1973, for example, homosexuality was classified as a diagnosable mental disorder by the American Psychiatric Association, rather than being recognized as a normal variation of sexual orientation. Finally, the different morals and standards of disparate cultural groups would mean that what was normal in one country or region would be considered abnormal in another.
Mental Disorders as Maladaptive Behavior
The maladaptive behavior perspective attempts to classify as mental disorders those behaviors that are dysfunctional. This refers to the effectiveness or ineffectiveness of a behavior in dealing with challenges or accomplishing goals. Typically discussed maladaptive behaviors include physically harmful behaviors, behaviors that prevent the person from taking care of themselves, those that prevent communication with others, and those that interfere with social bonding and relationships. As with our other perspectives, there are major concerns with this one.
First, how adaptive a behavior is hard to objectively quantify. This is due to the fact that the adaptive level of any particular behavior is based on both the situation and one’s subjective judgment. If a person is engaging in coercive behaviors, stealing, and lying to others, most people would say those are maladaptive behaviors (and depending on his age, qualify you for a diagnosis of Conduct Disorder or Antisocial Personality Disorder). But what if you learn that he was doing this to obtain food or medicine for his family? Would that still be maladaptive? One’s culture also plays a large role in determining the adaptiveness of a behavior.
For instance, in many Native American tribes, it is considered disrespectful to look an elder directly in the eye when talking to them. In other cultures, though, it would be considered disrespectful to not look them in the eye. Finally, this perspective clashes mightily with the statistical deviance perspective, in that statistically deviant behaviors (e.g., an IQ higher than 99% of the population) can be highly adaptive, and that numerous maladaptive behaviors (such as fear of public speaking) are quite common in the population as a whole.
Dimensional vs. Categorical Models of Mental Disorders
Another, different way to think about mental disorders is captured in the concept of categories versus dimensions. In a categorical model, psychopathology is dichotomous, either being present or not being present. In other words, you either have a mental disorder, or you don’t, there is no in-between. Dimensional models, on the other hand, acknowledge the fact that the vast majority of human behavior exists on a continuum, rather than the polarized view of the categorical model. What tends to be labeled as abnormal and unusual are merely the far ends of this normal curve of behavior. In this model, then, mental disorders are just extreme variations of normal psychological phenomena or problems that many or most of us experience.
The dimensional model has a very large amount of scientific support, particularly in the area of personality disorders. Support has been found for dimensional models of many other disorders, though, including anxiety, depressive episodes, and even psychotic disorders. Unfortunately, however, the real-world often requires caseness or non-caseness. In many instances one must be diagnosed with a particular mental disorder to obtain certain things, such as insurance reimbursement, special services at school, or disability benefits. This, subsequently, creates a tension between the need for categories and the lack of scientific support for them.
In part two, we will examine how the DSM-IV and upcoming DSM-5 define mental disorders. I will then conclude with an examination of what it means if we cannot scientifically define “mental disorders,” and how we move forward as a science.
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