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Don’t obsess over categorizing mental disorders: a psychiatrist’s perspective

Dr. Ralph Lewis
Written by Dr. Ralph Lewis

What is a mental disorder?

The question of what is a mental disorder and what is just an expected part of the “human condition” is an age-old, fraught and still unresolved question. Severe mental disorders are easy to recognize, but there is no clear line between normal and abnormal, and no definitive diagnostic test. So there is bound to be disagreement about the large swath of conditions in the grey zone.

Here’s a simple suggestion for making sense of the dilemma: Don’t try to categorize mental disorders. Even though the standard diagnostic manual of mental disorders, called DSM-5, does indeed categorize them, most experts agree that the classification system is best considered just a guideline, to be applied flexibly. Think more fluidly about most mental disorders being on a continuum with normality – one end of a spectrum for a given human trait / tendency. Moreover, many mental disorders also overlap with each other, such that an individual might easily be “diagnosed” with several “disorders.” Visualise the spectrum graphically: plotted as a bell curve, like for IQ scores or height or other normally distributed traits in the population.

Bell Curve


Understanding the spectrum

Let’s consider anxiety as an example: We all experience anxiety, and it’s often quite necessary that we do, as a certain amount of anxiety motivates us, and alerts us to be cautious. But some people are prone to experience anxiety more intensely, more frequently and for longer durations than others, causing those individuals greater distress and impairment in their functioning. Those people are at the right hand side of the bell-curve for the anxiety trait and might be considered to have a moderate “disorder.” They may be very sensitive, excessively prone to nervousness, stress and worry, emotionally reactive, uptight. Their sensitivity can be a positive trait too – they may be exquisitely emotionally attuned.

Those with the most severe, disabling anxiety are at the extreme end of the population spectrum for this trait – the right hand tail of the bell curve on the graph, and can be considered to have a severe disorder. The level of severity with which we set our criteria defining any degree of anxiety disorder will determine the percentage of the population who will be “diagnosed” as suffering from such a disorder, versus merely being considered normal people who are somewhat anxious. But remember, it’s not really a black or white question of “do you have a disorder or do you not?” It’s a shades-of-grey question of “to what degree is this trait / tendency causing you distress or impairing your functioning?”

At the other end of the curve (the left hand tail of our anxiety bell curve, if you will) are people who actually experience unusually little anxiety. This isn’t necessarily a good thing at all. Think of these people as relatively fearless and emotionally under-reactive. These people may take excessive risks and may be emotionally insensitive. At the extreme of this end of the spectrum, some of these people might even be predisposed to be psychopaths.

Of course, each of our full personalities, strengths and vulnerabilities is defined by a complex interplay of multidimensional traits, and no two of us are alike.

Why do extreme traits exist?

Why do extreme traits exist at all? Because otherwise we would have gone extinct as a species a long time ago. Diversity of traits is essential for a species to survive and evolve. While extremes of a trait might seldom be advantageous, they are an inevitable statistical result of genetic diversity, and that diversity is certainly adaptive for the species as a whole. The environment keeps changing, and a trait that is a weakness in one environment at one time and place (e.g. too cautious, or too exploratory) might well turn out to be a strength in another environment at another time and place.

So, have we artificially skewed our environment in modernity such that cultural and technological evolution has outstripped our much more slowly-evolving biological capacity to handle these kinds of stresses (time management, organization, attention, etc.)? Might this be one of the reasons why there seems to be a modern epidemic of mental illness? Or are we just getting better at understanding and recognizing mental health problems? A topic for another day…

About the author

Dr. Ralph Lewis

Dr. Ralph Lewis

Dr. Lewis is a psychiatrist at Sunnybrook Health Sciences Centre in Toronto, Canada, and an assistant professor in the Department of Psychiatry at the University of Toronto. His clinical work focuses particularly on two areas: youth psychiatry and psycho-oncology.

» Read his blog series, Finding Purpose