ADHD (Attention Deficit Hyper activity Disorder) causes are:

(1) Heredity: If parents or sibling of a child is with ADHD then the person has 4 to 5 time more prone towards ADHD.
(2) Brain function & structure: Certain area of the brain is smaller than the brain area of NON “ADHD”, Neurotransmitter imbalance can be seen in the case of ADHD.
(3) Premature Born: may lead towards the ADHD.
(4) Low Birth wt: May leads towards the ADHD.
(5) Brain damage: In the womb or Ist few years of life leads towards ADHD.
(6) Drinking Alcohol smoking & use of Drugs: has a bad effect on the working of nervous system and may lead towards the ADHD.
(7) Exposure of high level of toxic: Exposure to toxic in early age below 3 years has a bad effect on the working nervous system that may leads towards ADHD (e.g.lead)