There is o single cause for ADD/ADHD. A combination of psychological, biological and environmental factors contributes to this disorder.
Brain injuries due to birth trauma or pre-birth problems
Imbalance in the chemicals of the brain and neurological system of the child
Child’s temperament, as this contributes to child’s personality and attitude.
As a part of diagnostic process, the American Psychiatric Association’s DSM III-R has established a list of characteristics that the child must exhibit for duration of six months with onset before age seven.