For example, for a diagnosis of adult ADHD, one DSM-IV requirement is for the patient to have experienced onset of symptoms by age 7 (perhaps to distinguish it from confounding comorbidities that develop during or after adolescence). This seems unnecessarily restrictive and can be difficult to establish retrospectively. Even careful history-taking can be insufficient, as third-party observers are likely to be unavailable.9,13 Although recent studies have shown adult self-determined questionnaires to be an effective means of detecting ADHD impairment during childhood, many practitioners continue to question their validity.21 Proposals have been made to modify this age requirement, but agreement has not been reached on a new cutoff point (if one should be specified at all).
Because many “subthreshold” patients might benefit from pharmacotherapy, it has been suggested that the currently required number of DSM-IV criteria (six) should be relaxed. But what should that number be? Requiring only three criteria, researchers recently found, would result in 25% of all presenting patients qualifying for a diagnosis of ADHD.22 Most experts agree that a corresponding increase in psychostimulant use would be unjustified.
The willingness of practitioners to use the current DSM-IV criteria flexibly (eg, deciding what comprises a “clinically significant impairment”) will be determined by their level of comfort in diagnosing DSM-IV–defined disorders. Until continued research can provide more definitive diagnostic criteria for the adult with ADHD, a conservative approach may be advisable to avoid medicating patients unnecessarily.
Supplemental Rating Scales
Experts have developed several rating scales which, while not diagnostic, are nonetheless useful in identifying the adult who is impaired by ADHD but who may not strictly meet the DSM-IV criteria. These include:
• Wender Utah Rating Scale for Adult ADHD.23,24 One of the earliest and still most useful adjunctive rating scales for adult ADHD,23 this tool was originally developed to retrospectively identify childhood onset (before age 7) of ADHD symptoms. The original 61 items have been condensed and reorganized into a 25-item self-assessment questionnaire (see Table 123,24). The currently used Wender Utah scale seeks to elicit from the adult patient the core symptoms of ADHD.25
• Conners’ Adult ADHD Rating Scales (CAARS).26 This proprietary, 93-question, structured clinical interview allows the clinician to determine the presence of DSM-IV–defined symptoms of ADHD.27 Questions are grouped into nine symptom domains thought to encompass ADHD in adults, with responses categorized into four distinct problem areas21 (see Table 221,26,27). Although problematic responses appear to correlate highly with confirmed ADHD, a 15% misdiagnosis rate prevents use of the CAARS for definitive diagnosis.21
• Brown ADHD Rating Scale for Adults.28 This tool identifies five important symptom clusters (see Table 321,28). The Brown scale overlooks hyperactivity in adults and instead emphasizes executive functioning.
• Adult ADHD Self-Report Scale (ASRS-v1.1).29 This self-administered questionnaire, developed through the World Health Organization, assesses for 18 DSM-IV–designated ADHD symptoms, with the first six items found most predictive. If four of these six items are “scored” (ie, the patient responds “Often” or “Very often”), the assessment is considered highly consistent with adult ADHD, and further investigation is warranted. (For seven of the 18 items, an answer of “Sometimes” is also scored. See Table 4.29) Items 7 through 18 provide additional cues to distinguish specific symptoms or impairments.
No consensus exists regarding the reliable use of these rating scales to assist in the diagnosis of adult ADHD. As mentioned earlier, the role of patient self-reported symptoms of ADHD is subject to lingering controversy.27
ADHD Subtypes
Many practitioners find it aids diagnosis to divide ADHD into the subtypes shown in Table 519,27; subtypes 4 and 5 are often applicable in this patient population. According to Robison et al,30 however, women with ADHD are more likely to have the combined type (subtype 3) than men are (75% vs 62%, respectively), have a more complex presentation, and display greater impairment than men on all measures of ADHD symptoms.
Promise of Biomarkers
The neurobiologic basis of ADHD is poorly understood. Since medications known to have beneficial effects in ADHD alter dopamine levels,31 one prominent theory attributes the condition to dysfunction of dopamine neurotransmission and subsequent disruption of dopamine-modulated circuits among the frontal, striatal, and limbic regions of the brain.32 Early imaging studies using radioligands have shown a 70% increase in levels of the dopamine transporter molecule among subjects with ADHD, compared with non-ADHD controls.33 Subsequently, however, dopamine levels have been found to vary among subregions of the brain, suggesting that the explanation is probably more complex.32-34
ADHD medications also alter regulation of norepinephrine and possibly serotonin.31 The interplay in the brain between norepinephrine and dopamine is complex, and investigation of these processes is hampered by the current lack of a suitable radioligand that will bind selectively to the norepinephrine transporter molecule.35 Until an objective marker for ADHD is identified, the diagnosis of ADHD remains subjective and purely clinical.