N.I.C.E. GUIDELINES - EPIDEMIOLOGY - GIVES LIKELY RANGE OF PREVALANCE OF ADHD IN CHILDREN.

Key information about ADHD
Epidemiology

    The prevalence rate of ADHD is usually estimated at 3%-5% in school -aged children (American Psychiatric Association, 1994) although recent systematic reviews report ADHD prevalence estimates as wide as 2-18% (Rowland et al. 2002).
   
Around 1% of school-aged children have severe combined type ADHD (DSM-1V)/ hyperkinetic disorder (HKD - ICD-10); equivalent to approximately 73,000 children aged 6-16 in England and Wales.
   
Taking all forms of ADHD into account, perhaps 5% of school-aged children are affected - or 366,000 in England and Wales. Significant numbers remain undiagnosed.
   
The ratio of boys to girls is 4:1, with no social, economic or ethnic group bias in the general child population.
    
One third of affected individuals have at least one parent who suffers from similar symptoms.
   
ADHD is associated with: low birth weight (<1500g); environmental toxins; tobacco, alcohol and cocaine abuse during pregnancy (Milberger et al, 1996).
    
Although in the past it was thought that ADHD did not continue beyond adolescence, research has shown that a childhood diagnosis of ADHD has long term implications. More than 70% of those diagnosed with ADHD as children continue to fulfill diagnostic criteria in adolescence, and up to 65% of adolescents with ADHD still present with the disorder as adults (Jadad et al. 1999).
    
The number of prescriptions written for Methylphenidate in the UK increased from ~about 6000 in 1994 to ~ 345,000 children in 2003.

ABSTRACT FROM ROWLAND STUDY. 
"The epidemiology of attention-deficit/hyperactivity disorder (ADHD): a public health view."
Rowland AS, Lesesne CA, Abramowitz AJ.(2002)

MPH Program, Department of Family and Community Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, USA. arowland@salud.unm.edu
Abstract

Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder of childhood. However, basic information about how the prevalence of ADHD varies by race/ethnicity, sex, age, and socio-economic status remains poorly described. One reason is that difficulties in the diagnosis of ADHD have translated into difficulties developing an adequate case definition for epidemiologic studies.

Diagnosis depends heavily on parent and teacher reports; no laboratory tests reliably predict ADHD. Prevalence estimates of ADHD are sensitive to who is asked what, and how information is combined. Consequently, recent systematic reviews report ADHD prevalence estimates as wide as 2%-18%. The diagnosis of ADHD is complicated by the frequent occurrence of comorbid conditions such as learning disability, conduct disorder, and anxiety disorder. Symptoms of these conditions may also mimic ADHD. Nevertheless, we suggest that developing an adequate epidemiologic case definition based on current diagnostic criteria is possible and is a prerequisite for further developing the epidemiology of ADHD. 

The etiology of ADHD is not known but recent studies suggest both a strong genetic link as well as environmental factors such as history of preterm delivery and perhaps, maternal smoking during pregnancy. Children and teenagers with ADHD use health and mental health services more often than their peers and engage in more health threatening behaviors such as smoking, and alcohol and substance abuse. Better methods are needed for monitoring the prevalence and understanding the public health implications of ADHD. Stimulant medication is the treatment of choice for treating ADHD but psychosocial interventions may also be warranted if comordid disorders are present.

The treatment of ADHD is controversial because of the high prevalence of medication treatment. Epidemiologic studies could clarify whether the patterns of ADHD diagnosis and treatment in community settings is appropriate. 

Population-based epidemiologic studies may shed important new light on how we understand ADHD, its natural history, its treatment and its consequences.