Dalsgaard S, Thorsteinsson E, Trabjerg BB, et al. - Researchers conducted a nationwide cohort study of 1.3 million individuals in Denmark in order to determine age- and gender-specific incidence rates and cumulative incidences of the full spectrum of diagnosed mental disorders during childhood and adolescence. This cohort study was conducted in Denmark; all individuals born from January 1, 1995, through December 31, 2016, were included and were followed up from birth until December 31, 2016, or the date of death, emigration, disappearance, or diagnosis of 1 of the mental disorders examined (14.4 million person-years of follow-up). The analysis revealed that in girls and boys, the risk (cumulative incidence) of being diagnosed with a mental disorder before 18 years of age was 14.63% and 15.51%, respectively. They identified distinct age- and gender-specific patterns of occurrence across mental disorders in children and adolescents. Girls most frequently had anxiety disorders; boys showed the most common occurrence of attention-deficit/hyperactivity disorder (ADHD). Relative to boys, girls had a higher risk of schizophrenia, obsessive-compulsive disorder, and mood disorders. Boys vs girls showed earlier peaking of incidence in ADHD (8 vs 17 years of age), intellectual disability (5 vs 14 years of age), and other developmental disorders (5 vs 16 years of age). Before 6 years of age, the overall risk of being diagnosed with a mental disorder was 2.13% and was higher in boys than in girls.