Diagnosis of ADHD in Children

Although there is no clear demarcation between temperamentally impulsive, active and inattentive children and those who suffer from ADHD, those children whose behaviour interferes with their learning, social adjustment, peer relationships, self-esteem and family functioning warrant a thorough investigation. Arriving at a diagnosis is a lengthy and painstaking process based on a systematic, comprehensive, thorough and detailed neuropsychiatric work up, observation of the child in the school setting, and exclusion of medical conditions or circumstances that might produce a similar picture or exacerbate pre-existing ADHD. The symptoms must not be better accounted for by other psychiatric conditions (such a mood, anxiety, personality or dissociative disorders).

The definition and criteria for diagnosing ADHD are similar, but not identical, in both the international classification of diseases (ICD-10) (WHO, 1994) and the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association, 1994). The list of criteria for inattentiveness, overactivity and impulsivity is short but comprehensive. It is stipulated that the symptoms must have had an early onset (mean age is 4 years) and must have been present for more than 6 months, occurring across situations and falling along a continuum (deviant from age-based standards).

Co-morbidity:  ADHD Plus Other Psychiatric Disorders

All too often the unitary approach to diagnosing neuropsychiatric conditions prevails, and other co-morbid conditions are either overlooked or not paid sufficient attention. Because ADHD is a significant educational, social and emotional handicap, it is exceptional rather than the rule that it exists in pure form. Over 50% of sufferers will have either one or more of the following conditions at the same time (Bird et al, 1993):

• Specific learning difficulties
• Conduct disorder
• Oppositional defiant disorder
• Anxiety disorder
• Affective disorder
• Substance abuse
• Developmental language delay
• Obsessive compulsive disorder
• Asperger syndrome
• Tic disorder
• Tourette's syndrome

The degree of impairment depends on the type and number of co-existing conditions, which may require different or additional treatment. Co-morbidity does not explain causality; it merely states that two or more conditions are present at the same time.

Epidemiology of ADHD

The prevalence of ADHD used to be considerably different in the US and the UK, partly because of individual rigidity in applying clinical standards and partly owing to national practices. Historically, UK clinicians have been suspicious of ADHD as a primary condition and, therefore, approaches to diagnostic assessment vary widely between practitioners and centres. A rapprochment between the US and UK has emerged lately, made possible by the convergence of the diagnostic criteria of the ICD-10 and DSM-IV. This new consensus estimates prevalence in the UK at 6-8% of the child population, compared with 3-5% of UK children.

As with most neuropsychiatric conditions, the ratio of boys to girls is 3:1, with no social, economic or ethnic group bias in the general child population. However, in mental health clinics the ratio rises to between 6:1 and 9:1 (Cantwell, 1996) owing to referral bias (boys get referred more because they are more aggressive).

DSM-IV Distinguishes Three Types of ADHD:

1. Predominantly hyperactive-impulsive
2. Predominantly inattentive
3. Both hyperactive-impulsive and inattentive combined

The prevalence ratio is 3:1:2 in clinic populations and 1:2:1 in diagnosed community samples (Mash and Barkley, 1998). This suggests that the purely inattentive type is least likely to be identified and that screening for a possible diagnosis of attention deficit disorder (ADD) also occurs less often.