Attention Deficit/ Hyperactivitiy Disorder

What is ADHD?

1. Epidemiology

2. Etiology

3. References

Contents

1. Epidemiology

Attention Deficit/Hyperactivity Disorder (ADHD) is a neuro-psychiatric disorder that becomes apparent in the preschool or early school years (and by definition before the age of 7 years). Children present with inattention, and/or hyperactivity/impulsivity, depending on the type of ADHD they have. The prevalence of ADHD ranges from 4-12% depending on the population studied, and it is twice more common in boys than in girls. Several studies estimate that between 30-70% of children with ADHD continue to exhibit symptoms in the adult years.1

2. Etiology

Most substantiated causes of ADHD are in the realm of neurobiology and genetics. There is no evidence to support that ADHD arises purely from social factors or child-rearing methods. This is not to say however that environmental factors may not influence the severity of the disorder and degree of impairment the child may experience.

Genetics

Attention disorders often run in families. Studies indicate that 25% of close relatives of ADHD children also have ADHD, compared to 5% in the general population.2 Brain imaging studies of children with ADHD show differences in the frontal lobes, temporal gray matter, caudate nucleus, and cerebellum.3 Animal studies indicate imbalances between the norepinephrine and dopamine systems (both involved in the modulation of higher cortical functions) which may contribute to the pathogenesis of ADHD.4
       
Environment

There is not sufficient evidence to conclude that traumatic brain injury, food additives or sugar cause ADHD.

3. References:

National Institute of Mental Health @ http://www.nimh.nih.gov/health/publications/adhd/introduction.shtml 

1.   Silver LB. Attention-deficit hyperactivity disorder in adult life. Child and Adolescent Psychiatric Clinics of North America, 2000:9:3: 411-523
2.   Biederman J, et al. Family-genetic and psychosocial risk factors in DSM-III attention deficit disorder. Journal of the American Academy of Child and Adolescent Psychiatry, 1990; 29(4): 526-533
3.   Castellanos FX, et al. Developmental trajectories of brain volume abnormalities in children and adolescents with attention-deficit/hyperactivity disorder. Journal of the American Medical Association, 2002, 288:14:1740-1748
4.   Russell V, Allie S, Wiggins T. Increased noradrenergic activity in prefrontal cortex slices of an animal model for attention-deficit hyperactivity disorder--the spontaneously hypertensive rat. Behav Brain Res, 2000 Dec 20:117(1-2):69-74