By Marilynn Larkin
NEW YORK (Reuters Health) - The risk of being diagnosed with a mental disorder in childhood or adolescence depended in part on an individual's sex and age, in a nationwide Danish study of individuals with 27 types of mental disorders.
"One surprising finding was related to the epidemiology of early-onset schizophrenia (EOS)," Dr. Soren Dalsgaard of Aarhus University in Denmark told Reuters Health by email. "We found that females had a higher risk than males, and until now, EOS was thought to be a predominately male disorder."
"Another important and surprising finding was also related to sex-differences," he noted. "Neurodevelopmental disorders, by definition, have an onset in early childhood, often before age seven. In accordance with this, the majority of boys were diagnosed before age 10."
"Yet in females, many of these disorders were not diagnosed until late adolescence," he said. "This was perhaps most striking in attention-deficit hyperactivity disorder (ADHD), where the incidence peaked at age eight in males, (but) at age 17 in females. The difference suggests delayed detection of these neurodevelopmental disorders in females compared with males."
"In addition," he said, "we found that 1.45% of girls and 2.78% of boys had received a diagnosis of a mental disorder before age six. These estimates were previously unknown."
The study involved close to 100,000 young people (41% girls) diagnosed with a mental disorder before age 18 - about 15% of the overall population.
As reported online November 20 in JAMA Psychiatry, anxiety disorder was the most common diagnosis in girls (7.85%), while ADHD was the most common in boys (5.90%).
Girls had a greater risk than boys of developing schizophrenia (0.76% vs. 0.48%), obsessive-compulsive disorder (OCD; 0.96% vs. 0.63%), and mood disorders (2.54% vs. 1.10%).
"However, when looking at the details of OCD occurrence across different ages, we saw that the incidence and risk were very similar in boys and girls until age 10, after which the incidence rate increased more in females and peaked at age 16," Dr. Dalsgaard noted. "In males, it peaked at age 13 and then quickly declined. So, until age 10, the risk was equal, but at age 18, the risk was higher in females."
The incidence also peaked earlier in boys than girls for ADHD (age 8 vs. 17), intellectual disability (5 vs. 14), and other developmental disorders (5 vs. 16).
The overall risk of being diagnosed with a mental disorder before age six was 2.13%. As Dr Dalsgaard pointed out, the overall risk was higher in boys (2.78%) than in girls (1.45%).
Dr. Sara Gould, a clinical psychologist at Children's Mercy Kansas City, commented in an email to Reuters Health, "It is important to note that the rates reported reflect only diagnosed conditions for individuals seeking treatment. We know that the vast majority of mental health concerns go untreated, so actual rates are likely much higher. Similar studies have been conducted in the US with similar results (http://bit.ly/2Dro8FW). "
JAMA Psychiatry 2019.