Children who experience one mental health condition often face more than one — what is commonly referred to as having concurrent or co-occurring conditions. But just how common is this experience? A systematic review that combined data from 14 population-based surveys found that for children who met criteria for one mental disorder, 26.5% met criteria for two or more. Researchers have found even higher concurrent rates for children receiving mental health treatment services and for those in foster care.

Research on which disorders are more likely to co-occur is crucial for informing both prevention and treatment efforts. And the co-occurrence of substance use and other mental disorders has been particularly well studied. A systematic review of 21 population-based surveys compared young people with any substance use, including those whose use reached the level of a disorder, to individuals without any substance use. When young people had any substance use or a substance use disorder, their odds of having other disorders significantly increased. This included nearly eight times greater odds of also experiencing conduct, oppositional defiant or attention-deficit/hyperactivity disorders, slightly more than four times greater odds of co-occurring depressive disorders, and approximately two times greater odds of co-occurring anxiety disorders.

Data are more limited on the co-occurrence of disorders that do not involve substance use. A population-based survey of Puerto Rican children nevertheless provides insights on the overlap of conduct/oppositional defiant disorders, attention-deficit/hyperactivity disorder (ADHD), anxiety disorders and depression. Researchers found high levels of co-occurrence across all four conditions. But levels were particularly high for children whose primary diagnosis was conduct/oppositional defiant disorder — with anxiety disorders co-occurring for 55.3%, ADHD for 35.7%, and depression for 17.6%.

For more information, see Vol. 17, No. 3 of the Children’s Mental Health Research Quarterly.