ADHD appears to be highly heritable, although one-fifth of all cases are estimated to be caused from trauma or toxic exposure. Methods of treatment usually involve some combination of medications, behavior modifications, life style changes, and counseling.

The scientific consensus in the field, and the consensus of the national health institutes of the world, is that ADHD is a disorder which impairs functioning, and that many adverse life outcomes are associated with ADHD.

Symptoms
The most common symptoms of ADHD are distractibility, difficulty with concentration and focus, short term memory loss, procrastination, problems organizing ideas and belosngings, tardiness, impulsivity, and weak planning and execution. However, not all people with ADHD exhibit all symptoms. It is common for persons with ADHD to display symptoms only when they are doing tasks that require excessive, prolonged, or elevated levels of attention or are placed in environments that are too distracting, so that once stimulus is removed they function normally. But, in many cases this is not possible; intervention is needed to cope with these stimuli. The DSM IV categorizes the symptoms of ADHD into two clusters: Inattention symptoms and Hyperactivity/Impulsivity symptoms. Most ordinary people exhibit some of these behaviors but not to the point where they seriously interfere with the person's work, relationships, or studies or cause anxiety or depression. Children do not often have to deal with deadlines, organization issues, and long term planning so these types of symptoms often become evident only during adolescence or adulthood when life demands become greater. Inattention and "hyperactive" behavior are not the only problems with children with ADHD. ADHD exists alone in only about 1/3 of the children diagnosed with it. Many of these co-existing conditions require other courses of treatment and should be diagnosed separately instead of being grouped in the ADHD diagnosis. Some of the associated conditions are:

• Oppositional Defiant Disorder (35%) and Conduct Disorder (26%). These are both characterized by extreme anti-social behaviors. These disorders are frequently characterized by aggression, frequent temper tantrums, deceitfulness, lying, or stealing.
• Primary Disorder of Vigilance. Characterized by poor attention and concentration, as well as difficulties staying awake. These children tend to fidget, yawn and stretch, and appear to be hyperactive in order to remain alert and active.
• Bipolar disorder. As many as 25% of children with ADHD may have bipolar disorder. Children with this combination may demonstrate more aggression and behavioral problems than those with ADHD alone.
• Anxiety Disorders. Commonly accompany ADHD, particularly Obsessive-Compulsive Disorder. OCD is believed to share a genetic component with ADHD, and shares many of its characteristics. Although children with ADHD have an inability to maintain attention, conversely, they may also fixate. There is evidence of hypothalamic-pituitary-adrenal axis (HPA axis) abnormalities in ADHD patients due to stress.