Neurodegenerative illnesses of the basal ganglia and cerebellum, like Parkinson’s disease, are widely believed to be associated with aging. In a new study, however, researchers at the University of Utah Health have challenged that notion after probing the long-term effects of attention deficit hyperactivity disorder (ADHD) and its pharmaceutical treatment: stimulants.
According to researchers, ADHD, along with the use of stimulants like Ritalin, may increase the risk of developing Parkinson’s or similar disorders.
“This may be the first time where a childhood disease and its treatment may be linked to a geriatric expression of neurodegenerative disorder,” said Glen Hanson, a professor of Pharmacology and Toxicology at U of U Health.
ADHD is characterized by difficulty with regulating attention and excessive activity. As of 2017, close to 6.5 million children have been diagnosed with the neurodevelopmental disorder in the U.S., a 42 percent increase over the past 8 years.
For the study, statewide medical records of 31,769 patients with ADHD, collected between 1996 to 2016, were examined from the Utah Population Database. 4,960 of participants were prescribed stimulants. The sample was then compared to a non-ADHD population of 158,790 participants with similar age and gender. All participants chosen had no history of neurodegenerative illness or substance abuse.
The findings showed that ADHD patients were more than twice as likely to develop early-onset Parkinson’s and Parkinson-like diseases when compared to the non-ADHD group of the same age and gender. Moreover, the risk for patients prescribed stimulants was 6 to 8 times higher.
“If we were to follow 100,000 adults over time, in one year we would expect 1 to 2 people will develop Parkinson’s disease before age 50,” said Karen Curtin, an author of the study. “If we were to follow 100,000 adults prescribed treatment for ADHD over time, we estimate that over a year 8 to 9 patients will develop Parkinson’s disease before age 50.”
Researchers note that although the study adds weight to previous findings, which have linked stimulant misuse to the onset of neurodegeneration, the results are preliminary and require further research.
“The study results should be considered preliminary. This study may be limited by the misclassification of non-ADHD subjects, who were diagnosed with the disorder outside of Utah, missed or incorrect diagnosis of Parkinson-like disease symptoms and the lack of information on the duration of use and dosage of ADHD medication prescribed,” Stacy Kish, a science writer at U and U Health, concluded in a press release.
The findings were published in the journal Neuropsychopharmacology.