Sander van der Wel/Wikimedia Commons, public domain
Source: Sander van der Wel/Wikimedia Commons, public domain

Is mental illness real? It’s a question as old as the idea of mental illness itself. Most famously addressed in the 1961 book, The Myth of Mental Illness, psychiatrist Thomas Szasz argues that the idea of classifying psychological and emotional difficulties as “illnesses” takes away personal agency. Instead of holding people personally and ethically responsible for their actions, he contends, doctors attempt to “treat” the person, often with medications. Proponents of diagnosing mental illness, on the other hand, argue that mental disorders are as real as physical diseases and diagnosing them allows people to get the care they need.

To be clear, nobody doubts the fact that psychological symptoms are absolutely real and that people are truly suffering. The question is whether it makes sense to refer to these experiences as “illnesses” in the same way we think about HIV, cancer, or even the flu.

To fully understand the issue, it's important to consider how mental disorders are diagnosed. The bible of mental illnesses is the Diagnostic and Statistical Manual of Mental Disorders—or DSM for short—which is currently in its 5th edition. If you were to visit a psychologist’s office, one of the first things that he or she would do is assess your symptoms. After a thorough interview, the psychologist would sit down, crack open the DSM, and determine whether your symptoms met the criteria for any of the disorders it contains. To qualify for a diagnosis of Major Depressive Disorder, for instance, you must have at least five of the nine possible symptoms listed in the DSM, these symptoms must last for at least two weeks, and they must impair your functioning. So, if you were to complain of a few weeks of intensely sad mood, loss of interest in things that previously gave you pleasure, staying in bed all day, feeling completely worthless, contemplating suicide, and difficulty concentrating, the psychologist may diagnose you with Major Depression.

What's important to note is that the diagnosis is determined primarily by the symptoms. If a patient has these symptoms and they impair functioning, he or she generally will get the diagnosis. This is very different from how most people think about the nature of disease. Despite the fact that the causes of physical diseases can take many forms, most people think of diseases as external invaders of the body like bacteria, viruses, or parasites. We say that someone has a disease if he or she has been subject to that external invader. We can only be said to have a cold if our body has been invaded by a virus. That's because sneezing, a hacking cough, and difficulty breathing can be caused by other things besides a viral infection, like allergies or asthma. So, unlike mental disorders, physical illness are typically identified by their etiologies—a fancy word for causes—rather than solely by their symptoms.

Because mental disorders are generally identified on the basis of their symptoms, a mental illness diagnosis doesn't necessarily explain a person's symptoms, it only describes them. If you go to the doctor complaining of upper respiratory symptoms and he or she diagnoses you with the flu, this provides an explanation for your symptoms—the flu virus is the cause of your coughing and sneezing. But, if your psychotherapist diagnoses you with Major Depression Disorder, this doesn’t provide an explanation for your mood symptoms. The label "Major Depression" is simply a shorthand summary of the symptoms you probably already know you have.  This doesn't mean that mental illnesses have no causes—clearly both important environmental as well as genetic factors are often involved—but a diagnosis by itself doesn't tell you what those causes are, which could differ from case to case.

There’s a good reason for this reliance on symptoms to diagnose mental disorders. When mental health professionals began diagnosing mental illness about a hundred years ago, it was on the basis of the causes or etiologies of those illnesses, just like for physical diseases. Given the state of the science at that time, however, there was a big problem: Nobody could agree what the causes of any particular disorder were. The field was splintered into different schools of thought. The psychoanalysts believed that mental illnesses were often caused by unconscious sexual issues stemming from childhood. Behavior therapists believed that many disorders were primarily dysfunctional behaviors learned as a result of inconsistent reinforcement and punishment in the home. Cognitive therapists later hypothesized that mental illnesses were often due to particular negative views of the self, known as schemas. As a result of all of this disagreement, diagnosis was unreliable. If you went to three mental health providers complaining of the exact same problem, you would likely receive three different diagnoses. To remedy this situation, with the publication of the third edition of the DSM in 1980, the American Psychiatric Association changed over to the current, much more reliable, symptom-based system.

The fact that a mental illness diagnosis primarily describes, rather than explains, a person’s symptoms doesn’t make it useless, however. A diagnosis accomplishes two very important things. First, it helps direct the therapist toward what treatments work for that disorder. As a psychologist, if I know that my patient has the particular combination of symptoms that would allow me to diagnose Major Depression or Panic Disorder or Obsessive-Compulsive Disorder, I can turn to the empirical research about what techniques have helped others with that diagnosis in the past, rather than reinventing the wheel each time. Personally, if I were a patient, I’d want to know that what my therapist were doing was something that had been shown to work for others with problems similar to my own. As such, diagnostic labels facilitate an evidence-based approach to treatment. Second, a diagnosis can help to unlock access to care. For better or worse, healthcare organizations sometimes require a person to qualify for a mental disorder diagnosis in order to receive certain kinds of treatment. This isn’t always the case, of course, but it sometimes is. 

So, are mental illnesses real? Yes. But we need to understand their limitations. They’re generally not external invaders of the body like viruses or bacteria, and they don’t necessarily absolve people of responsibility for their actions. But they are useful descriptions of the very real suffering that people can experience. Even given its limitations, the concept of mental illness has helped to structure the mental health field for decades, helps connect people to the care they need, and is unlikely to go away any time soon.


David B. Feldman is a Professor of Counseling Psychology at Santa Clara University and co-author of Supersurvivors: The Surprising Link Between Suffering & Success (HarperCollins).  Follow his work at

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