ReviewAttention-deficit/hyperactivity disorder in adults: an overview
Introduction
Some researchers have asserted that because ADHD usually remits in adulthood (Hill and Schoener 1996), adult ADHD should be rare and of little concern to the practicing clinician. Others have claimed many cases of ADHD persist into adulthood Barkley 1997, Faraone in press, Spencer et al 1994b. They stress the diagnostic continuity of ADHD throughout the life span and assert that clinically referred adults have the same syndrome that has been so well validated in pediatric cases. To be clear, this debate addresses the diagnosis of retrospectively diagnosed childhood onset ADHD, when the childhood diagnosis has been made through retrospective accounts and the current presentation shows a continuation of the syndrome into adulthood. Proponents of ADHD as a valid adult diagnosis do not suggest that ADHD arises de novo in adulthood.
Resolving the debate about adult ADHD will benefit both clinicians and researchers. If the diagnostic continuity of child and adult ADHD can be established, clinicians will have a foundation for generalizing the vast pediatric ADHD research literature to adult patients. Because effective treatment plans presuppose accurate diagnoses, clinicians need to know if adults who present with what appears to be childhood onset ADHD truly have the disorder. Diagnostic accuracy is paramount for all disorders, but it is even more important for ADHD, which is frequently accompanied by substance abuse and usually treated with stimulants.
Clarifying diagnostic continuity will also allow a generalization of research results from adults to children. This direction of generalization is especially important for research that may be considered acceptable in adults but premature or unethical in children. Examples include functional imaging with radioactive isotopes and the testing of new drugs. In the latter case, having a valid diagnosis of adult ADHD would allow researchers to show efficacy in adults and then use that information to justify trials in children.
This article addresses the validity of adult ADHD using the validity criteria of Robins and Guze (1970). In their view, the validity of any psychiatric disorder derives not from a single study, but from a pattern of consistent data. For psychiatric disorders, standard validation criteria include clinical correlates, family history, treatment response, laboratory studies, course, and outcome.
Section snippets
Clinical correlates
The DSM-IV recognizes three subtypes of ADHD: a predominantly inattentive subtype, a predominantly hyperactive-impulsive subtype, and a combined subtype (American Psychiatric Association 1994). These categories acknowledge clinical heterogeneity and reflect a change in emphasis from earlier definitions that stressed motoric symptoms to the current nosology, which emphasizes deficits in the regulation of cognitive function. These changes have particular relevance to adult ADHD because
Family history
Because genes affect one’s susceptibility to ADHD (Faraone and Biederman 1999), family studies provide a method of assessing the validity of adult ADHD. If ADHD persists into adulthood, then the parents of ADHD children and the children of ADHD adults should show an increased risk for ADHD. Many case-control family studies show that the former prediction is true. The parents of ADHD children are more likely to have ADHD than are the parents of non-ADHD children (Faraone and Biederman 1994).
In
Treatment response
An overwhelming amount of data from close to 200 controlled clinical trials unequivocally documents the efficacy of stimulant medications in the treatment of children and adolescents with ADHD (Spencer et al 1996). Because approximately 70% of ADHD children show a therapeutic response to stimulant medication, some researchers have looked to studies of stimulant drugs in adult ADHD in the hope that a clear-cut response to stimulant medication would clarify the validity of adult ADHD.
Four initial
Laboratory studies
Although there is no laboratory test of ADHD for either children or adults, laboratory measures provide useful clues about the etiology of adult ADHD and its validity as an outcome of the childhood disorder. This section examines three laboratory approaches that have been applied to adult ADHD: molecular genetics, neuropsychologic assessment, and neuroimaging.
Course and outcome
Do ADHD children grow up to become ADHD adults? If adult ADHD is a valid disorder, then follow-up studies of ADHD children should show that they grow up to become ADHD adults and that their persistence of ADHD symptoms exceeds that seen in an appropriate control group. Prospective follow-up studies are not clouded by the ambiguities of retrospective reports. Thus, they are an essential for validating the adult ADHD diagnosis. If prospective studies do not find ADHD persisting into adulthood,
Summary and future directions
This article has examined the validity of adult ADHD using the validity criteria of Robins and Guze (1970): clinical correlates, family history, treatment response, laboratory studies, course, and outcome. Table 1summarizes our review by giving each domain of study a score: ++ means that results strongly support the validity of adult ADHD, + means that results support the validity of adult ADHD, ? means that results are equivocal, − means that results do not support the validity of adult ADHD,
Acknowledgements
This work was supported in part by National Institute of Mental Health Grants Nos. R01MH57934, R01HD37694, and R01HD37999 (SVF).
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