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How Common Are Psychiatric Disorders?

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Charles F. Zorumski, M.D. is the Samule B. Guze Professor and Head of the Department of Psychiatry at Washington University in St. Louis – School of Medicine, where he is also Professor of Neurobiology.  In addition, he is Psychiatrist-in-Chief at Barnes-Jewish Hospital and Director of the Washington University McDonnell Center for Cellular and Molecular Neurobiology.  Eugene H. Rubin, M.D., Ph.D., is Professor and Vice-Chair for Education in the Department of Psychiatry at Washington University in St. Louis – School of Medicine.  Together they wrote, Demystifying Psychiatry: A Resource for Patients and Families, which offers a straightforward description of the specialty and the work of its practitioners.  In the excerpt below we learn about the prevalence of psychiatric disorders.

Studies examining the frequency of psychiatric disorders in various populations are done by epidemiologists.  These are scientists who investigate patterns of illnesses, as well as their causes and prevention.  They play key roles in describing epidemics and in identifying factors associated with the spread of a disease in a population. Ideally, they would like to study an entire population, such as the entire US population or the entireDemystifying Psychiatry cover image population of New York City.  However, that is usually impossible (due to economic costs and logistical challenges associated with such a massive research undertaking), so epidemiological studies rely on obtaining representative “random samples of the people of interest. Based on these random samples, epidemiologists use statistics to estimate the frequency of an illness in a large population (called the “incidence” of the disorder).  Admittedly, this is a crude description of the science of epidemiology.  Nonetheless, for our discussion, these definitions will suffice.

How Common Are Psychiatric Disorders?

There have been several studies examining the frequency of psychiatric disorders in US populations.  Examples include the Midtown Manhattan Study, which was conducted in the 1950s, and the Epidemiological Catchment Area (ECA) Study, which was conducted in the 1980s.  More recent studies include the National Comorbidity Study (NCS), the National Comorbidity Study-Replication (NCS-R), and the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), among others.  These large studies have provided important insights into the nature of psychiatric disorders in the United States…the data from the NCS and NCS-R obtained from 1990 to 1992 and 2001 to 2003, respectively, indicate that the prevalence of psychiatric disorders in the adult US population (ages 18-54 years) is estimated to be about 30% (i.e., about one in three persons has a diagnosable psychiatric disorder during those periods).  Based on other data, the prevalence may approach 50% when considered from a lifetime perspective (i.e., one-half of the US population is likely to have a psychiatric disorder at some point in their lives).  Those are staggering figures and are a strong indicator that almost every person in the United States has some contact, knowingly or not, with persons with mental illness. When we consider the complexity of the brain systems that may be involved in various psychiatric disorders, these figures make sense….our brain motivation and reward systems are critical for our survival. However, these systems can be easily hijacked by drugs of abuse; this likely contributes to the prevalence of the various substance abuse disorders.  Similarly, our brains’ emotional systems are critical for how we function and survive.  For example, some degree of anxiety can be healthy and can help motivate us to protect ourselves against an obvious threat.  But the systems governing anxiety and fear are highly regulation and can be turned on and off by a variety of stimuli, both appropriately and inappropriately.  It is not too much of a stretch of the imagination to see that perturbation or overuse of these systems can interfere with our everyday functions (e.g. too much anxiety can be crippling).  The same may be true for brain systems involved with mood or perceptions.

You’ll recall that some good news/bad news scenarios came out of NCS and NCS-R.  The good news indicated that the prevalence of mental illness in the US adult population did not increase over the 1990s and that treatment for mental disorders increased over that time from about 12% of the population to 20%.  The bad news was that, despite the increase in treatment, almost two out of three patients with a psychiatric diagnosis did not receive treatment.  Additionally, about half of the patients treated for a mental disorder actually did not have a diagnosable mental disorder, possibly reflecting the tendency of some physicians to treat symptoms and not disorders.  For example, a person may report feeling sad to a primary care doctor, and then be prescribed an antidepressant.  However, another doctor, inquiring a little more deeply, may find that this person does not meet diagnostic criteria for a clinical depression and thus probably does not require pharmacologic treatment.  As noted earlier, sadness does not equal depression.  Sadness without other symptoms suggestive of depression may be a healthy and realistic response to a situation.  With a little bit of support and time, the sadness is likely to resolve.

The results from the NCS-R are consistent with other studies.  For example, a recent survey by the World Health Organization (WHO) indicated that about 25% of the US population has a psychiatric disorder, but that only about 15% of these people actually get treatment.  The perverse “good news” in the WHO study is that those who were defined as “seriously ill” had about a one in two chance of getting treatment.  That is, if you are really sick, you have a higher likelihood of getting treatment than if you are more mildly ill; unfortunately, a 50% chance of getting treatment means that a lot of seriously ill individuals are not getting the care they need.  Taken together, these are sobering data and indicate that psychiatric disorders are very common but poorly understood and very poorly treated in the US health care delivery system.

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