A history of attention-deficit hyperactivity disorder (ADHD) and its medications was tied to a higher risk of Parkinson's and Parkinson-like diseases, researchers reported.
ADHD patients had a 2.4-increased risk of basal ganglia and cerebellum diseases before age 66 compared with non-ADHD individuals of the same sex and age, reported Glen Hanson, DDS, PhD, of University of Utah Health in Salt Lake City, and colleagues in Neuropsychopharmacology.
The estimated risk was six to eight times higher for ADHD patients prescribed stimulant medications like methylphenidate (Ritalin, Concerta, Daytrana, Metadate, and Methylin), mixed amphetamine salts (Adderall), and dexmethylphenidate (Focalin), and was especially pronounced in these patients between the ages of 21 and 49.
The study stemmed from previous research about abuse of amphetamines and risks of developing Parkinson's-related disorders, Hanson said in an interview with MedPage Today. "We didn't even think there would be an ADHD link, and certainly not at this level."
The study incorporated the Utah Population Database, which contains vital and medical records of more than 11 million Utah residents. The researchers studied patients born between 1950 and 1992 who were at least 20 years old by the end of 2011 and who had no prior diagnosis of Parkinson's or Parkinson-like diseases.
Hanson and co-authors identified an ADHD population of 31,769 patients -- 4,960 of whom were prescribed stimulant medications (amphetamine salts n=2,716; methylphenidate n=1,941; both n=303) -- matching them on sex and age with 158,790 comparators; patients with a history of drug or alcohol abuse were excluded.
In both groups, about 89% were white, and over 90% had no history of tobacco use. ADHD patients were more likely than comparators to have had a psychotic condition diagnosed (12.6% and 2.1%, respectively).
Patients with ADHD showed a 2.4-fold increased risk of basal ganglia and cerebellum diseases (95% CI 2.0-3.0; P<0.0001), after adjusting for tobacco use and psychotic conditions. Among ADHD patients prescribed psychostimulants, the risk was especially pronounced between the ages of 21 and 49, at 8.6 times higher (95% CI 4.8-15.6; P<0.0001).
"These findings may point to a common, yet hitherto unknown, link between basal ganglia and cerebellum diseases -- in particular, Parkinson's disease -- and ADHD," said Joseph Classen, MD, of the University of Leipzig in Germany, who was not involved in the study. "It should alert the community to be particularly careful about the indication for prescribing medications for ADHD."
Studies of methamphetamine abuse have shown a relationship between methamphetamine dose and the size of an echogenic region projecting onto the substantia nigra, Classen noted.
"We found that the larger the methamphetamine dose, the more extended was the size of the substantia nigra area as assessed with transcranial ultrasound," he told MedPage Today. "As a similar abnormality has been noted in Parkinson patients and individuals at risk for Parkinson's, this finding indicated a possibly harmful effect of methamphetamine on the integrity of the substantia nigra, although it remained unknown if and how this observation was related to the higher risk of Parkinson disease in past consumers of methamphetamine."
The association between ADHD patients prescribed psychostimulants and higher risk of diseases of the basal ganglia and cerebellum may reflect more severe ADHD, Hanson and co-authors noted.
"We are not implying that ADHD treatment should not be done," Hanson said. "Treatment is still a benefit, especially for children who cannot control their ADHD symptoms. Medication really should be considered on a case-by-case basis."
These results are preliminary and further research needs to be done, he added. Because ADHD was not widely acknowledged as a psychiatric diagnosis until 1968 and usually is identified in children, the study was limited to people who developed onset basal ganglia and cerebellum diseases before age 65.
This project was funded by the National Institute on Drug Abuse. Support for the Utah Population Database was provided by the National Cancer Institute, the University of Utah Program in Personalized Health, the National Institutes of Health, the National Center for Research Resources, and the Utah State Department of Health.
The authors reported having no competing interests. medpagetoday.com/neurology/...
