What is the most common mental illness disorder that develops in children?

The most common mental illness disorder that develops in children is Attention Deficit Hyperactivity Disorder (ADHD). ADHD is characterized by persistent patterns of inattention and/or hyperactivity-impulsivity that interferes with functioning or development. It is widely recognized and diagnosed in both clinical and educational settings, making it the most prevalent mental health condition among children.

In contrast, while disorders like autism spectrum disorder, generalized anxiety disorder, and depression can also affect children, they do not occur with the same frequency as ADHD. Autism spectrum disorder, for example, is less common and has distinct diagnostic criteria that apply to a smaller subset of children. Generalized anxiety disorder can affect children, but it tends to manifest at a later age and is not as frequently diagnosed in very young children as ADHD. Depression also occurs in children, but the prevalence is lower compared to ADHD.

The high visibility of ADHD symptoms in various environments, such as school and home, contributes to its recognition as the most common mental health disorder in childhood.