Attention Deficit Hyperactivity Disorder (ADHD) is a medical disorder that affects development and functions of the brain. There are several causes associated with the occurrence of ADHD including genetic effects, exposure to toxic substances and brain injury among others. Broad studies carried out on genetic relationship within families, adopted children, between twins and molecular genetics research confirms that ADHD is a hereditary medical disorder. Family studies show that, “over 25% of the first Degree relatives of the families of ADHD children also had ADHD, whereas this rate was only about 5% in each of the control group” (My ADHD, 2010). High occurrences of ADHD in families indicate that it is a hereditary condition. To confirm whether it may be a social issue, psychological studies of ADHD on adopted children in relation to their biological and adaptive parents indicates that, hyperactive children relates more to their biological parents than to the adaptive parents. These findings prove that, ADHD is not due to social influences but a genetic disorder. Further studies on twins, both identical and non-identical twins show that, “…82 percent concordance rate for ADHD in identical twins as compared to a 38 percent concordance rate for ADHD in non-identical twins” (My ADHD, 2010). Similarity the severity of the ADHD condition in identical twins is due to same genetic make-up, hence giving concrete evidence that ADHD is an inheritable disorder. Eventually, molecular studies have isolated dopamine genes that are responsible for the ADHD, thus most probable cause of ADHD lies in genetics. Another cause of ADHD is exposure to toxic substances. Research findings indicate that, there is positive correlation between pregnant mothers exposed to toxic substances such as lead, nicotine and alcohol, and susceptibility of their children to develop ADHD. These substances “…can be toxic to the developing brain tissue and may have sustained effects on the behavior of the children exposed to these” (My ADHD, 2010). This result supports only the cause of ADHD in children but do not give explanation to the cause of ADHD in adolescents. Brain injury also causes ADHD but in rare cases. Despite the availability of credible scientific studies, there are numerous misconceptions surrounding the causes and treatment of ADHD, which boils down to controversy. ADHD Library (2004) acknowledges the controversy that, while National Institute of Health supports that diet can cause hyperactivity, Food and Drug Administration discredits the claims that, diet and certain food additives cannot contribute to hyperactivity in children. Contradiction by great authorities as these, results into misconception concerning ADHD. Another misconception is that ADHD is a childhood disorder only, and affects boys more than girls. Studies show that ADHD does not only occur in children, but also in adults, and affects girls and boys equally. Other misconceptions claim that poor parenting, too much television watching, playing computer games and hormonal imbalance cause ADHD. All these are misconceptions, which distort scientific evidences. Genetic inheritance is the most plausible explanation of the cause of ADHD since scientific evidenc