Among patients with fibromyalgia syndrome (FMS), nearly half (44.72%) screened positive for adult attention-deficit/hyperactivity disorder (ADHD), according to South African researchers. The two conditions may be linked by shared mechanisms of cognitive impairment, as noted in a study published in Pain Medicine.
“These results indicate that the co-occurrence of adult ADHD in FMS may be highly prevalent and may also significantly impact the morbidity of FMS,” wrote authors led by Roland van Rensburg, MBChB, who is in private practice in Lyttelton, South Africa. “The shared symptoms of impaired cognition experienced by both FMS and ADHD patients could indicate a possible association between these disorders.”
Prior research has indicated a higher frequency of ADHD among FMS patients. But in that research, investigators used now-outdated diagnostic criteria for FMS that lacked a cognitive assessment. Cognitive symptoms are prevalent complaints in FMS patients. These symptoms include difficulty with concentration and attention, forgetfulness, and problems with word-finding and word fluency.
“Self-reported cognitive impairment (also referred to as “fibro-fog”), can be more disabling to [FMS] patients than their widespread pain,” wrote Dr. van Rensburg and co-authors. “However, impaired cognition often goes underrecognized and undertreated,” due in part “to the complexity of the neurophysiological assessment of dyscognition in FMS patients.”
The investigators also noted that some research has associated ADHD with pain disorders via shared mechanisms such as dopamine dysregulation.
A strong association
For this observational study, Dr. van Rensburg and colleagues recruited 123 patients (88% female, average age of approximately 50 years) who had been previously diagnosed with FMS at a chronic pain practice in Pretoria, South Africa. Patients were screened for adult ADHD using the World Health Organization Adult ADHD Self Report scale v1.1. Cognitive assessment was based on the 2011 modified American College of Rheumatology criteria and the Revised Fibromyalgia Impact Questionnaire.
Overall, 44.72% of patients with FMS screened positive for associated adult ADHD, which suggested a “strong association” between the disorders, the researchers noted. Of the 55 patients who screened positive, 7.27% reported a previous diagnosis of adult ADHD, with a median duration of 7 years (2 to 10 years).
In addition, 91% of FMS patients who were found to have ADHD also screened positive for anxiety, markedly more than in the FMS-only group (71%).
Because previous research hadn’t used cognitive assessment in FMS diagnostic criteria, the potential overlap of FMS and cognitive impairment has probably been underestimated. “Consequently, the presence of ADHD and other cognitive symptoms in FMS patients may have been underreported,” wrote Dr. van Rensburg and coauthors.
On the upside, the finding of adult ADHD and FMS comorbidity may have positive implications for drug therapies. While dopaminergic stimulants, such as methylphenidate, have improved cognitive impairment in ADHD patients, patients with chronic pain have also been shown to have lower D2-receptor binding and presynaptic dopamine activity, the researchers noted. In one small study, for example, FMS patients who received daily methylphenidate showed significant improvements in concentration, energy, and mood over the 30-day treatment period.
“This may represent an additional therapeutic approach,” Dr. van Rensburg and coauthors noted. “The possible sharing of underlying central neurotransmitter mechanisms in patients with FMS and ADHD needs further investigation.”
Given the results of this study, the authors concluded that all patients with FMS should be screened for comorbid adult ADHD.