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How common is childhood mental illness? If you asked 20 mental health clinicians, you could easily get 20 different answers. This lack of consensus does not mean clinicians aren’t being well trained, or that they have poor memories. Rather, this fundamental question remains largely overlooked by psychiatric research.

But it’s a critically important question. If we want to assess how well we are meeting children’s mental health needs, we must know how many need help. The answer also has profound implications for the best approaches to prevention and treatment, and even for public acceptance of mental illness. Yet medical records are little help, offering a notoriously inadequate picture of the rates of common mental illnesses like depression and anxiety. Meanwhile, government agencies such as the National Institutes of Health do not regularly track rates of psychiatric diseases, because routine tracking on such a large scale would involve extensive diagnostic interviewing and would be quite costly.

In the United States, the answers we have come from a patchwork of psychiatric epidemiologists around the country. Estimates from such studies vary somewhat, based upon whether the sample assessed is urban or rural, the type of interviewer, whether the researchers interview children, parents, or both, and which illnesses are assessed.

Some consistent patterns nonetheless emerge: A recent National Academy of Sciences report summarized results from over 50 such community studies and found that at any given time about 17 percent of U.S. children — roughly 1 in 6 — meet the criteria for a common psychiatric disorder. With approximately 73 million children under the age of 18 in the U.S., this suggests that over 10 million children are affected at this very moment.

But this estimate represents a snapshot: It only includes those who are ill at a given moment in time. From a public health perspective, it is also important to take the long view, and discover how many children experience mental illness at some point in their childhood.

As it turns out, this is not a trivial consideration. A small number of studies, including those of our own research group, have followed children over a number of years, tracking rates of mental illness across childhood in the same children. Those studies suggest that mental illness is far more common than many think. Our work with the Great Smoky Mountains study showed that 60 percent of children experience a psychiatric disorder by adulthood. Those disorders include a wide range of conditions, ranging from rare illnesses such as autism or schizophrenia to more common conditions such as depression, anxiety, and substance abuse.

This striking analysis suggests a radical change in perspective on childhood mental illness: Mental illness in childhood is not uncommon or rare. On the contrary, mental illnesses, particularly common disorders such as depression and anxiety, are as much a feature of childhood as common physical illnesses.

And even these analyses may underestimate the number of children truly affected by mental illness. We’ll examine that issue in a future post.

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The Long View

How Common Is Childhood Mental Illness?

Mental illness affects children much more often than you might think.