This post was co-written by Eugene Rubin MD, PhD and Charles Zorumski, MD.
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% of 2516 million children and youth aged 5 to 24 years have a mental disorder, and about 1.2% have substance use disorder. The prevalence of mental disorders ranged from 6.8% of those 5 to 9 years old to 13.6% 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% of those 5-9 years old, and increased to 3.35%, 4.34%, and 4.58% 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% of 5-9 year olds, 2.87% of those 10-14 years old, and decreased to 1.61% of those 20-24 years old.
Depressive disorders demonstrated dramatic changes in prevalence with age. The prevalence was less than 0.1% in those aged 5-9 years. It increased to about 1% for those 10-14 years old, 2.69% for those 15-19, and 3.85% 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% for bipolar disorder and 0.24% 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% 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% 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% of YLD, skin and subcutaneous diseases for 10.5%, nutritional deficiencies for 8.96%, and musculoskeletal disorders for 7.54%.
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 8th most disabling illness and conduct disorder was the 9th. For those aged 10-14 years, conduct disorder was the third-most disabling condition, with anxiety disorders 4th and depressive disorders 8th. For those aged 15-19, depressive disorders were the secod-most disabling condition, with anxiety disorders 3rd and conduct disorders 8th By age 20-24 years, depressive disorders remained the 2nd most disabling medical condition, with anxiety disorders 4th, and drug use disorders 6th.
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% of disability caused by all medical illnesses for the population as a whole. The YLD related to mental disorders endured by those age 5 to 24 account for almost 25% 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.”
Psychiatry Essential Reads
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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