How Many Young People Have a Mental Health Disorder?

This article was co-written by Eugene Rubin M.D., Ph.D., and Charles Zorumski, M.D.

Many mental disorders begin during childhood, adolescence, and early adulthood. How common is mental illness in young persons? How disabling are these disorders?

These questions are addressed in an important paper by Christian Kieling, Peter Szatmari, and colleagues in JAMA Psychiatry, based on data from the 2019 Global Burden of Disease Study. In order to study differences among age groups, they analyzed data for four groups: 5- to 9-year-olds, 10- to 14-year-olds, 15- to 19-year-olds, and 20- to 24-year-olds.

The Global Burden of Disease Study categorizes mental disorders into the following groups: anxiety disorders, attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder, bipolar disorder, conduct disorder, depressive disorders, eating disorders, schizophrenia, developmental intellectual disability, and other mental disorders. It classifies substance use disorders separately into alcohol use disorder and drug use disorders.

Prevalence Data

Data from the 2019 Global Burden of Disease Study indicate that about 11.6 percent of 2516 million children and youth aged 5 to 24 years have a mental disorder, and about 1.2 percent have substance use disorder. The prevalence of mental disorders ranged from 6.8 percent of those 5 to 9 years old to 13.6 percent of those 20 to 24 years old.

Importantly, there were age-dependent patterns of prevalence for specific mental disorders. For example, anxiety disorders occurred in 1.32 percent of those 5-9 years old, and increased to 3.35 percent, 4.34 percent, and 4.58 percent for those 10-14 years old, 15-19 years old, and 20-24 years old, respectively. This pattern was different from the prevalence for ADHD, which occurred in 2.14 percent of 5-9 year olds, 2.87 percent of those 10-14 years old, and decreased to 1.61 percent of those 20-24 years old.

Depressive disorders demonstrated dramatic changes in prevalence with age. The prevalence was less than 0.1 percent in those aged 5-9 years. It increased to about 1 percent for those 10-14 years old, 2.69 percent for those 15-19, and 3.85 percent for those 20-24.

Both bipolar disorder and schizophrenia had very low prevalence in those 14 and younger. The prevalence of these psychotic disorders increased to 0.72 percent for bipolar disorder and 0.24 percent for schizophrenia in those aged 20-24.

Alcohol use and drug use disorders had similar age-related patterns with low prevalence prior to age 15 and increasing to about 1.5-2 percent in those ages 20 to 24.

Knowing the prevalence of these disorders at various ages provides baseline information that can be used to evaluate the effectiveness of both prevention trials and treatment trials.

What About Associated Disability?

A common measure of disability used by researchers is “years lived with disability (YLD).” In this case, disability refers to years lived with less than full health. The degree of disability is quantified by a disability weight factor that is determined for each condition. For those 5-24 years old, the Kieling team calculated that mental disorders are responsible for more than 20 percent of all YLD from medical illnesses.

As a group, mental disorders account for more disability in this age range than any other category of medical disorders. By comparison, neurologic disorders account for 10.6 percent of YLD, skin and subcutaneous diseases for 10.5 percent, nutritional deficiencies for 8.96 percent, and musculoskeletal disorders for 7.54 percent.

The investigators also examined which specific medical disorders had the most associated YLD in each age group. Several psychiatric conditions were in the top 10 for each age group. For those 5-9 years old, anxiety disorders were the eighth most disabling illness, and conduct disorder was the ninth. For those aged 10-14 years, conduct disorder was the third-most disabling condition, with anxiety disorders fourth and depressive disorders eighth.

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For those aged 15-19, depressive disorders were the second-most disabling condition, with anxiety disorders third and conduct disorders eighth. By age 20-24 years, depressive disorders remained the second most disabling medical condition, with anxiety disorders fourth, and drug use disorders sixth.

Does this mean that a young person with anxiety disorder is more disabled than a young person with cancer? No, but because there are many more young persons with anxiety disorders than with cancer, the total amount of disability due to anxiety disorders surpasses the total amount of disability due to cancer.

Overall Importance

Mental disorders account for more than 20 percent of disability caused by all medical illnesses for the population as a whole. The YLD related to mental disorders endured by those aged 5 to 24 account for almost 25 percent of all disabilities caused by mental disorders.

In an accompanying commentary, David Saunders, Frances Knapp, and Jeremy Veenstra-VanderWeele emphasize that the data regarding psychiatric disability in young people should lead to “further research… to understand who are the most vulnerable, and, therefore, who are in most need of prevention and intervention—and when.”

Early interventions may decrease the prevalence of psychiatric disorders. For example, interventions that target anxiety disorders and depressive disorders have the potential to substantially decrease disability associated with these two common conditions.

Investing in prevention and treatment studies of psychiatric disorders that are common in young people should lead to significant decreases in disability caused by these disorders. The more society recognizes the tremendous amount of disability caused by psychiatric illness, the more attention will be devoted to these disorders.

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