Roland van Rensburg, MBChB

Patients with fibromyalgia syndrome (FMS) have a high co-occurrence of adult attention-deficit/hyperactivity disorder (ADHD) and should be evaluated for that likelihood, a new study concludes.

“This new research now highlights the probable association of these 2 conditions, based on similar underlying neurotransmitter dysfunctions, and clinical cognitive impairment,’’ lead author Dr. Roland van Rensburg, MBChB, University of Pretoria, South Africa, told MD Magazine.

“Clinicians, especially those in primary health care, should screen all FMS patients for the presence of associated ADHD,’’ he added.

Van Rensburg and his team identified common characteristics of FMS and ADHD. Then they set out to evaluate the likely co-occurrence of the disorders and to determine how that combination might impact patients.

FMS, which is characterized by chronic musculoskeletal pain, leaves individuals with cognitive impairments such as difficulty concentrating, forgetfulness and lack of word fluency, the authors wrote. This impairment, known as dyscognition or “fibro-fog,” can be more disabling than the pain of FMS itself, but often goes under-recognized and undertreated.

ADHD also involves impaired cognition. Previous research has suggested that ADHD may be associated with pain disorders through shared mechanisms such as dopamine dysregulation, the researchers said.

"ADHD in adulthood manifests mostly as the inattentive presentation, with impaired cognition as a core symptom. Likewise, a key feature of FMS is cognitive impairment,’’ van Rensburg said. “The current understanding is that both these conditions have similar underlying neurotransmitter dysfunctions, most notably dopamine and serotonin.’’

To test for possible co-occurrence of FMS and ADHD, the researchers studied 123 patients who were attending a chronic pain practice in Pretoria, South Africa, from Dec. 2015—April 2016.

The participants had been previously diagnosed with FMS. They were evaluated for ADHD using the World Health Organization Adult ADHD Self Report scale. The severity of their FMS was assessed with the Revised Fibromyalgia Impact Questionnaire (FIQ-R) and their cognitive health and levels of anxiety and depression were also evaluated.

Almost half of the patients — 44.7% — screened positive for adult ADHD. The individuals who had both FMS and a positive adult ADHD screening test scored higher on the FIQ-R, indicating they were experiencing a greater impact from FMS than participants with FMS alone.

Anxiety in the combined group was markedly higher than in the FMS group, with 90.9% of participants screening positive. Patients in the combined FMS/ADHD group also reported greater cognitive impairment, the team found.

"Impaired cognition is an overlapping feature of both FMS and adult ADHD, and has been attributed to both conditions separately,’’ van Rensburg said.

Van Rensburg said the researchers were surprised by how many of the FMS participants tested positive for adult ADHD.

"A small study suggested that it might be around 25%,’’ van Rensburg said.

He added that future studies should include a comprehensive clinical assessment by an expert clinician to confirm the presence of ADHD. In this study, a self-reporting questionnaire was used.

Asked whether the similarities between FMS and ADHD might lead to a single treatment for both disorders, van Rensburg said: "The common key feature of impaired cognition, and possible shared neurotransmitter dysfunctions, argues that there may be drugs that are effective for both FMS and adult ADHD when they occur concurrently.’’

He noted that a previous observational case study suggested such a path when researchers found that ADHD patients with unexplained fatigue, widespread musculoskeletal pain, or a pre-existing diagnosis of chronic fatigue syndrome or FMS not only saw improved symptoms of ADHD on stimulant medication, but also improvement of pain and fatigue.

"Further studies are needed to explore this therapeutic avenue,’’ van Rensburg said.

The research, "Screening for Adult ADHD in Patients with Fibromyalgia Syndrome" was published in Nov. 1, 2017, in Pain Medicine.

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