Epidemiology

ADHD is manifest in approximately 4-12% of children between the ages of six and 12 years. The variance is due to changing diagnostic criteria over time, variations of assessments in different settings, and geographical areas, and estimates based on referrals. Over 500 articles and 10 published rating scales were reviewed for the development of the American Association of Pediatrics' (AAP) clinical guidelines for evaluation and treatment of ADHD [AAP, 2000; Brown et al, 2001], and this research, based on diagnostic criteria in the DSM-III, DSM-III-R, or DSM-IV, gave the 4-12% figure quoted above.

The most prevalent co-morbid conditions in children identified by Brown et al were oppositional defiant disorder, conduct disorder, and anxiety. Each co-morbidity occurred in approximately 25-33% of patients diagnosed with ADHD. Approximately 20% of patients had depressive or learning disorders. In community settings, males were diagnosed at least three times as often as females [AAP 2000; Brown et al, 2001].

ADHD in girls is a more serious risk factor for substance abuse than in boys [Biederman et al, 2002; Brown et al, 2001]. Between 15% and 35% of affected children have one or more additional psychiatric disorders (e.g., anxiety, depression, oppositional defiance/conduct disorders, learning disabilities, tic disorder, or substance abuse). The inattentive subtype of ADHD appears to be associated more often with anxiety, depression, and learning disabilities, but with fewer behavioral problems. The hyperactive-impulsive and combined subtypes are more often associated with antisocial personality disorder in adulthood, conduct disorders, and oppositional defiant disorders [Biederman et al, 2002; Brown et al 2001; Guevara and Stein, 2001; Wilens et al, 2002;].

Between 50% to 75% of people with ADHD have the combined subtype. The inattentive subtype is representative of about 20%-30% of those with ADHD. Less than 15% of ADHD meets the criteria for the hyperactive-impulsive subtype [Wilens et al, 2002]. While the combined subtype is the most prevalent subtype in both genders, girls with ADHD are about 2.2 times as likely to primarily have the inattentive subtype. Perhaps, due to the lower rates of defiance in girls with ADHD than in boys, ADHD is more likely to be recognized in boys than in girls. [Biederman et al, 2002; Wilens et al, 2002].

ADHD in Adults

There are no definitive epidemiological studies to indicate prevalence of ADHD in adults or persistence from childhood. Two longitudinal studies have followed "hyperactive" children and adolescents diagnosed with ADHD based on older criteria. The findings on persistence were widely discrepant, 11% and 60% persistence, respectively.

Other diagnoses from these studies reported in adulthood included antisocial personality disorder and substance abuse. More recent studies indicate persistence of symptoms of childhood ADHD into adulthood may be as high as 66-75% and that between 1% and 6% of the general adult population has appreciable evidence of ADHD [Wender et al, 2001; Wilens et al, 2002].

Changing diagnostic criteria, the subjectivity involved in the application of severity to diagnostic criteria in the DSM-IV, and the lack of adult-specific diagnostic criteria for ADHD, including appreciation of experiential vs. performance criteria and gender-related differences, continue to hamper analysis of historical ADHD data.

A diagnosis of ADHD should be considered in adults who have lifelong problems with inattention, disorganization and executive function, cognitive restlessness, vocational and academic underachievement based on their intelligence and education, substance abuse, stability in relationships (e.g., multiple divorces), or who consistently engage in thrill-seeking and risky behaviors [Faraone et al, 2000; Quinn and Nadeau, 2002; Searight et al, 2000; Szymanski and Zolotor, 2001; Wender et al, 2001; Wilens et al, 2002].

References

American Academy of Pediatrics. Clinical Practice Guideline: Diagnosis and evaluation of the child with attention-deficit/hyperactivity disorder. Pediatrics. 2000; 105 (5): 1158-1170.

Biederman J, Mick E, Faraone SV et al. Influence of gender on attention deficit hyperactivity disorder in children referred to a psychiatric clinic. Amer J Psychiatry. 2002; 159: 36-42.

Brown RT, Freeman WS, Perrin JM et al. Prevalence and assessment of attention-deficit/hyperactivity disorder in primary care settings. Pediatrics. 2001; 107 (3): e43.

Faraone SV, Biederman J, Spencer T et al. Attention-deficit/hyperactivity disorder in adults: an overview. Biol Psychiatry. 2000; 48: 9-20.

Guevara JP, Stein MT. Evidence based management of attention deficit hyperactivity disorder. BMJ. 2001;223:1232-1235.

Quinn PQ and Nadeau KG. Gender Issues and AD/HD: Research, Diagnosis and Treatment. Silver Spring, MD: Advantage Books, 2002.

Searight HR, Burke JM, and Rottnek F. Adult ADHD: Evaluation and treatment in family medicine. Amer Fam Phys. 2000; 62:2077-2086.

Szymanski ML, Zolotor A. Attention-deficit/hyperactivity disorder: management. Amer Fam Phys. 2001; 64:1355-1362.

Wender PH, Wolf LE, Wasserstein J. Adults with ADHD: an overview. Annals of the New York Academy of Sciences. 2001; 931: 1-16.

Wilens TE, Biederman J, and Spencer TJ. Attention deficit/hyperactivity disorder across the lifespan. Annual Review of Medicine. 2002; 53: 113-131.

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