A recent paper by Margaret Sibley and colleagues addresses a key issue in the diagnosis of adult ADHD. Is it sufficient to only collect data from the patient being diagnosed or are informants useful or, perhaps, essential, for diagnosing ADHD in adults. Dr. Sibley presented as systematic review of twelve studies that prospectively followed ADHD children into adulthood. Each of these studies asked a simple question: What faction of ADHD youth continued to have ADHD in adulthood. Surprisingly, the estimates of ADHD’s persistence ranged from a low of 4% to a high of 77%. They found two study features that accounted for much of this wide range. The first was the nature of the informant; did the study rely only on the patient’s report or were other informants consulted. The second was the use of a strict diagnostic threshold of six symptoms. When they limited the analysis to studies that used informant and eliminated the six symptom threshold, the range of estimates was much narrower, 40% to 77%. From studies that computed multiple measures of persistence using different criteria, the authors concluded: “(1) requiring impairment to be present for diagnosis reduced persistence rates; (2) a norm-based symptom threshold led to higher persistence than a strict six-symptom DSM-based symptom count criterion; and (3) informant reports tended to show a higher number of symptoms than self-reports.” These data have clear implications for what clinicians can do to avoid false positive and false negative diagnoses when diagnosing adult ADHD. It is reassuring that the self-reports of ADHD patients tend to underestimate the number and severity of ADHD symptoms. This means that your patients are not typically exaggerating their symptoms. Put differently, self-reports will not lead you to over-diagnose adult ADHD. Instead, reliance on self-reports can lead to false negative diagnoses, i.e., concluding that someone does not have ADHD when, in fact, they do. You can avoid false negatives by doing a thorough assessment, which is facilitated by some tools available at www.adhdinadults.com and described in CME videos there. If you think a patient might have ADHD but are not certain, it would be helpful to collect data from an informant, i.e., someone who knows the patient well such as a spouse, partner, roommate or parent. You can collect such data by sending home a rating scale or by having the patient bring an informant to a subsequent visit. Dr. Sibley's paper also shows that you can avoid false negative diagnoses by using a lower symptom threshold than what is required in the diagnostic manual. In fact, the new DSM 5 lowered the symptom threshold for adults from six to five. Can you go lower? Yes, but it is essential to show that these symptoms lead to clear impairments in living. Importantly, this symptom threshold refers to the number of symptoms documented in adulthood, not to the number of symptoms retrospectively reported in childhood. To be diagnosed with ADHD in adulthood, one must document that the patient had at least six impairing symptoms of ADHD prior to the age of 12.
Sibley, M. H., Mitchell, J. T. & Becker, S. P. (2016). Method of adult diagnosis influences estimated persistence of childhood ADHD: a systematic review of longitudinal studies. Lancet Psychiatry 3, 1157-1165.