Several important mental health disorders, such as depression and eating disorders (see see Eating Disorders), often develop during childhood and adolescence. Some disorders, such as autism, develop only during childhood.

With a few exceptions, symptoms of mental health disorders tend to be similar to feelings that every child experiences, such as sadness, anger, suspicion, excitement, withdrawal, and loneliness. The difference between a disorder and a normal feeling is the extent to which the feeling becomes so powerful as to overwhelm and interfere with the activities of normal life or cause the child to suffer. Thus, doctors must use a significant degree of judgment to determine when particular thoughts and emotions stop being a normal component of childhood experience and represent a disorder.

Some disorders affect mainly behavior, causing children to disturb others, including teachers, peers, and family members. These disorders, called disruptive behavioral disorders, include attention-deficit/hyperactivity disorder (the most common one—see Learning and Developmental Disorders: Attention-Deficit/Hyperactivity Disorder), conduct disorder, and oppositional defiant disorder.

In children, some disorders affect both mental health and overall development. These disorders, called autism spectrum disorders (see Learning and Developmental Disorders: Autism Spectrum Disorders), include autism, Asperger's syndrome, pervasive developmental disorder not otherwise specified, Rett syndrome, and childhood disintegrative disorder. The pervasive developmental disorders are a group of related conditions that all involve some combination of impaired social relationships, a restricted range of interests, abnormal language development and use, and, in some cases, intellectual impairment.

Last full review/revision February 2009 by Hugh F. Johnston, MD