ATTENTION DEFICIT HYPERACTIVITY DISORDER

Attention Deficit Hyperactivity Disorder



Attention Deficit Hyperactivity Disorder

Introduction

ADHD is a complex disease that has no single cause. It is a neurological disorder linked to abnormal development and brain function. Thus, the researchers found that among children or adults with ADHD, the brain areas responsible for attention, organizational skills and movement control are activated abnormally or have an unusual anatomy (Barkley, 1997). They also noted an imbalance in the levels of certain chemical messengers (neurotransmitters) in the brain such as dopamine and nor epinephrine.

Hereditary factors are major contributors to the onset of ADHD. In addition, most children with ADHD have at least one family member who also suffers. Several genes involved in ADHD have been identified, but genetic factors alone do not explain the disease. In addition, exposure to certain toxic substances (alcohol, tobacco, lead, pesticides, etc) during fetal life could explain 10% to 15% of cases. Other environmental factors probably contribute to the onset of the disease in genetically predisposed children. Furthermore, injury or infection of the brain, lack of oxygen at birth, or other complications at birth may increase the risk of ADHD (Biederman, 1995).

Attention Deficit Hyperactivity Disorder has a strong genetic component. However, not all children who possess the genetic component will develop problems associated with the disorder. This paper uses the multidimensional framework, encompassing the genetic, neurological, psychosocial, cultural and environmental basis, to explain why not all children predisposed toward ADHD develop problems. The paper also provides an overview of the effects of ADHD and the treatment modalities currently in use.

Genetic Basis

Family transmission of ADHD has been supported by a number of studies (Faraone & Biederman, 1994). The rate of ADHD in children of parents with ADHD is higher than for the rate of ADHD in other relatives (Biederman et al., 1995). A parent with ADHD has a 57% chance of having an ADHD child. Adoption studies (Cantwell, 1975), twin studies (Gilger, Pennington, & DeFries, 1992), and international adoption studies (van den Oord, Boomsma, & Verhulst, 1994) also have identified strong genetic components of ADHD. Approximately 80% of the inattention-hyperactivity-impulsivity trait is due to genetic factors (Barkley, 1998a). While there is some evidence that extreme scores on this trait increase the genetic contribution, Barkley does indicate that this later point is debatable.

Environmental factors account for a much smaller percentage of the variance of the inattention- hyperactivity-impulsivity trait, approximately 6% (Sherman, Iacono, & McGue, 1997; Silberg et al., 1996). Persistent ADHD-into adulthood-may has a stronger familial etiology than non persistent ADHD (Bierderman, Faraone, Keenan, Steingard, Tsuang, 1991). In their comprehensive genetic study, Faraone et al. (1995) found that boys with ADHD have diverse etiological risk factors, while girls appear to have a stronger familial type with strong heritability factors. Although genetic heritability of ADHD is high, these findings are complicated by the high degree of comorbid conduct, mood, and anxiety disorders found in individuals with ADHD (Biederman, Faraone, Keenan, Steingard et al., 1991).

Neurological Basis

Neuroscientists have taken an interest in understanding the neurobiological basis of ...