Children who are diagnosed with ADHD are often diagnosed with another form of mental illness. Some disorders that may be diagnosed in association with ADHD include:

• Anxiety disorders. Conditions marked by debilitating or disruptive fears or anxieties. They occur in 25 percent of children diagnosed with ADHD, according to the National Alliance on Mental Illness (NAMI) and the National Institute of Mental Health (NIMH).
  
  
• Conduct disorder. Condition marked by significant antisocial behavior such as theft and physical violence. It occurs in 20 to 40 percent of children with ADHD, according to NIMH.
  
  
• Depression. Persistent feelings of sadness that interfere with a person’s ability to enjoy life. It occurs in about one-quarter of children with ADHD, according to NAMI.
  
  
• Learning disabilities. Conditions marked by low academic performance despite normal range of intelligence. About 20 to 30  percent of children diagnosed with ADHD also have a learning disability, according to NIMH. Many children with ADHD also have the reading disorder dyslexia.
  
  
• Bipolar disorder. A condition in which the patient’s mood cycles between intense highs (mania) and lows (depression). ADHD and bipolar disorder in children have many similar symptoms. There are no reliable statistics on the number of children with both conditions.
  
  
• Oppositional defiant disorder (ODD). A pattern of negative or hostile behavior toward authority figures. It appears in about half of all children with ADHD, according to NAMI.
  
  
• Tourette’s syndrome (TS). Neurological disorder marked by compulsive muscular or vocal tics. Although only a small percentage of patients with ADHD have Tourette’s, at least half of those diagnosed with Tourette’s also have ADHD, according to NAMI.