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Child and Adolescent Psychiatry, Ealing Hospital, London UB1 3HW, UK
Correspondence to: 61 Carthew Road, London W6 0DU, UK
| INTRODUCTION |
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The diagnosis and treatment of ADHD is a perplexing area for the child and adolescent psychiatrist, and in the opinion of some clinicians and researchers the check-lists of the DSM-IV and ICD-10 do little justice to the psychosocial and behavioural aspects of hyperkinetic activities.5 Moreover, review of the published work is hampered by the numerous changes in diagnostic criteria over the years.6 The notion that ADHD phenomena reflect other disorders, rather than being core components of a nosologically separate identity, persisted (particularly in the UK) long after the discovery by Bradley in 1937 that stimulant medication has a calming effect on hyperactive children.7 However, as the diagnostic tools have become more robust and the evidence to support pharmacological treatment has become stronger, the doubters are now in a minority. The attention dyscontrolimpulsivityhyperactivity triad is widely accepted not only as a formal mental disorder but also as one whose diagnosis and management, both pharmacological and psychosocial, can offer profound benefit for the child and family.
Because ADHD was diagnosed and managed principally by child and adolescent psychiatrists, the long-term fate of the patients suffered relative neglect. The likelihood of remission seemed to be supported by a steady reduction in symptoms over time.8 However, the dearth of information has been substantially remedied over the past two decades and the possibility of ADHD as an adult diagnosis is gaining groundopening treatment options for those affected. This paper explores existing knowledge and potential areas for further research.
| EPIDEMIOLOGY OF CHILD TO ADULT ADHD |
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If ADHD were largely confined to childhood we would expect to see the prevalence rates dropping sharply in late adolescent samples. The epidemiological research to date does not indicate such a phenomenon. In an American community sample of children in their final year at school (mean age 18 years) the prevalence was 1.5% overall, and 2.6% in the males.14 Furthermore, prospective studies of ADHD children show that, although there is a trend towards amelioration of symptoms, a substantial proportion continue to have at least one disabling symptom in adolescence and young adulthood. A New York cohort of children aged 612 with ADHD was followed up longitudinally, and after 10 years about a quarter still met the diagnostic criteria.15 A similar study in Montreal gave even more striking results; two-thirds of children with ADHD continued to be disabled by the disorder in early adulthood.16 There is little doubt that, for some at least of those affected in childhood, ADHD continues into adult life.
| AETIOLOGY |
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Other information has come from functional neuroimaging with positron emission tomography. Zametkin et al. studied adults20 and children21 with ADHD to see whether glucose metabolism in their brains differed from that in normal controls. Both adults and children with ADHD proved to have subnormal metabolism in the premotor and superior frontal cortex. Again this finding has yet to be replicated.
There is also strong evidence that perinatal insults increase the prevalence of ADHD. In a casecontrol study Mick and others found a 2-fold increase associated with prenatal smoking and a 2.5-fold increase associated with inutero exposure to alcohol.22 The same group also found casecontrol evidence for a correlation between low birthweight (<2500 g) and an up to 3-fold excess risk of ADHD.23 Their work built on earlier reports24 suggesting that these three factors are all potential causes of neurological damage leading to the phenotypic picture of ADHD.
The final biological link in the aetiological chain comes from twin studies, with their ability to differentiate environmental from genetic influences. In a study of monozygotic (MZ) and dizygotic (DZ) twin pairs Goodman and Stevenson25 showed a MZ:DZ ratio of 51:33, and from this they extrapolated the heritability of inattention and hyperactivity traits to be in the region of 3050% compared with a 030% influence for environmental factors.
Despite the above evidence, the neurobiological theory of ADHD is well short of proof. As indicated, much of the work is preliminary, and replication when attempted has not always been successful.26 With imaging reports readers need to bear in mind the vast amount of information analysed and the fact that, with conventional statistical testing, significant differences are to be expected for one of every twenty comparisons. Zametkin et al., for example, looked at 60 areas of the brain and found differences in only 4 (3 would be expected by chance alone). We must also consider the possibility that such changes are the result of the illness (with repeated insults to the brain) rather than the cause.
| THE FEATURES OF ADHD AS CHILDREN GROW UP |
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The core triad of featuresinattention, impulsivity, hyperactivityapplies to both children and adults, and they are chronic and stable.29 A reported reduction in symptoms with advancing age may be explained by acquisition of cognitive strategies to ameliorate these features.30 In adults, inattention and impulsivity seem more stable markers of ADHD than hyperactivity. Poor concentration at work (and during enjoyable leisure activities), daydreaming and forgetfulness suggest inattention, whilst poor tolerance to frustration, easy loss of temper and exceptional impatience suggest inattention and impulsivity. Hyperactive manifestations such as fidgeting and restlessness may also be present. These features can lead to difficulties in interpersonal relationships, in maintaining a satisfactory work record and in enjoying life in general. Such symptoms can, of course, arise in anyone at some time. Prerequisites for the adult diagnosis are temporality (i.e. the symptoms must have been present since childhood), pervasiveness and functional impairment. Unfortunately, the instruments developed to aid diagnosis are not totally specific and are particularly error-prone in patients with comorbid psychiatric illness. Furthermore, the boundary between ADHD and antisocial personality disorder is unclear; for both, the essential criteria include presence since childhood, functional impairment, interpersonal difficulties and intrapsychic distress. Just as in young populations where hyperactive children may in fact have a primary behavioural disorder, not all inattentive or impulsive adults should be assumed to have ADHD.
To help resolve the clinical dilemmas, four rating scales have been developed from the child criteria in DSM-IV, and each has been found valid.31 The adult attention deficit disorder evaluation scale (A-ADDES), developed by McCarney and colleagues is most closely related to the child criteria whereas the Brown Attention Deficit Disorder Scales and the Attention Deficit Scales for adults give more emphasis to the temporal and cognitive features of the adult presentation of ADHD. The WenderUtah self-rating scale, which looks at the symptoms of ADHD against an adult background,32 can be used to make a retrospective diagnosis of ADHD in childhood, thus fulfilling the requirement for temporality. There is little to choose from between these scales, however.
| SOCIAL DIFFICULTIES FOR THE ATTENTION-DEFICIENT ADULT |
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Troubles at home in maintaining and sustaining family relationships are most sharply highlighted in the prospective sample followed up by Weiss and Hechtman.36 The difficulties arose not only from the personal struggle to maintain relationships but also from the problems of coping with their similarly affected children. Moreover, adults with ADHD seem to produce more than the average number of offspring,37 and an individual who personally struggles with inattention and impulsivity will have difficulty in mustering the parenting skills to deal with an ADHD-disordered child. Clearly there is substantial social morbidity in this group.
| COMORBID PSYCHIATRIC SYMPTOMS IN ADOLESCENTS AND ADULTS |
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The rate of substance misuse in the ADHD population is also said to be raised.41 Not all researchers, however, have confirmed this association and some have noted it only in adults who continue to experience core symptoms of ADHD.15 Alcohol consumption in pregnancy is a risk factor for ADHD, so perhaps one disorder predisposes to the other or they are intertwined. Since conduct disorder is associated with ADHD in children it is not surprising that adolescents with ADHD tend to show antisocial personality traits.42 This is reflected in the greater rates of criminal involvement in young adulthood.43 The correlation between ADHD and adult psychiatric comorbidity is stronger in females then in males: girls with ADHD had a greater risk of psychiatric admissions in adulthood and this was significantly increased if they also had a history of conduct problems.44
The research to date, although not conclusive, points to a link between ADHD in adults and a broad range of other psychiatric illsnotably affective, substance-misuse and antisocial disorders. Probably most adults with ADHD seek advice from primary care or psychiatric services at some point in their lives, and in a patient with alcohol dependence or personality disorder the ADHD is easily missed. Clinically the diagnosis is important to make in view of the prognostic and treatment implications.
| MANAGEMENT OF ADULT ADHD |
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Non-stimulant medications have attracted more interest in adults than children with ADHD, especially antidepressants, but no long-term randomized trials of commonly used antidepressants have been reported. Noradrenergic antidepressants have also been reported beneficial in early work, but not all experts are persuaded: Wender argues that adults with ADHD are more prone to the side effects of these compounds and that there is no overall benefit.49
In children the possibility of using antihypertensives has been explored and clonidine is considered a useful second-line when stimulants are contraindicated (e.g. in severe tic disorders). Clonidine has not been investigated in adults with ADHD. Some small studies suggest benefit from beta-blockers against impulsive symptoms.50 The novel antidepressant bupropion has also been shown effective in treating the core adult ADHD symptoms,51 and this is particularly noteworthy in view of the stimulant-like structure of this drug. Clarification of the value of nonstimulant medication in this group of patients is important since many are substance misusers in whom stimulant therapy is undesirable.
Medication is not the only therapeutic option, though it is much more fully researched than others. Several experts in the area of adult ADHD back the use of psychotherapeutic interventions. Also, positive results are emerging from cognitive approaches to the treatment of adult ADHD.52
| CONCLUSION |
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