Is Persistence of ADHD into Adulthood a Matter of Diagnosis?

It has long been estimated that four to 77% of children with ADHD continues to manifest symptoms into adulthood. However, a new review of longitudinal studies found that symptoms persist in 40 to 50% of those whose adult ADHD is diagnosed on the basis of self- and informant ratings, the presence of impairment, and an age-appropriate symptom threshold.

Margaret Sibley, PhD, Department of Psychiatry and Behavioral Health, Center for Children and Families, Florida International University, Miami, and colleagues undertook the review to determine whether the apparent drop in ADHD diagnoses among adults with childhood ADHD reflects true remission, or a reduced number of diagnoses being made.

To ascertain how diagnostic methods may have influenced estimated persistence of ADHD into adulthood, the researchers examined studies of persistent ADHD conducted in the last two decades. They identified 17 with methodology that met their inclusion criteria, comprising a total of 12 samples of children with ADHD who were prospectively followed into adulthood.

The studies that reported low rates of symptom persistence relied on self-report and required a six-symptom Diagnostic and Statistical Manual of Mental Disorders (DSM) threshold. Sibley and colleagues pointed out that utilizing these factors to establish a diagnosis counters prevailing definitions of mental disorders, "which emphasize establishing the presence of developmentally atypical symptoms that cause harmful dysfunction through multi-method assessment."

"A careful read of these studies highlights a crucial issue in psychiatry: the difference between having a disorder and receiving a diagnosis," Sibley and colleagues said.

According to the team, “The more recent findings from birth cohort studies revisit questions about the origins and chronicity of ADHD, yet they might reflect instability in diagnosis rather than disorder.”

In contrast to well established and validated procedures for diagnosing ADHD in children, the researchers noted that research on adult ADHD has failed to yield the defining symptoms, or to give direction on the best means to collect, review, and integrate data upon which to base the diagnosis.

"Unless diagnostic procedures for ADHD in adults are refined, persistence and prevalence estimates will continue to vary widely, reflecting inconsistency in diagnostic methods across studies," Sibley and colleagues warn.

When only the studies that did not rely on self-report were considered, the estimated range of persistence was between 12 and 77%, and when the six-symptoms DSM threshold was removed from consideration, the range was from 40 to 77% across ten estimates. Although few studies were found to have included self and informant ratings, presence of impairment and age-appropriate symptom threshold, those that did had indicated persistence rates of 40 to 50%.

From their findings, Sibley and colleagues concluded that ADHD should continue to be viewed as a chronic disorder for many individuals. They do not rule out the possibility of new cases of ADHD emerging in adults, but suggest that these may follow from subclinical symptoms in childhood that were not detected until environmental demands or risk factors increased later in life.

"Undertaking further studies without sound diagnostic methods could lead to continued confusion about the nature of ADHD across development, including the questionable view that ADHD typically remits by adulthood," Sibley and colleagues caution.

Their findings “Method of Adult Diagnosis Influences Estimated Persistence of Childhood ADHD: A Systematic Review of Longitudinal Studies,” were reported in the December issue of The Lancet Psychiatry.

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