September 14, 2018
The risk of early-onset Parkinson’s disease and similar disorders is 2.4 times greater among patients with attention deficit disorder (ADHD or ADD) than it is among individuals of the same gender and age without ADHD. What’s more, there may be a staggering six- to eight-times higher likelihood of Parkinson’s among patients treated with stimulant medications – methylphenidate (e.g., Concerta, Daytrana, Ritalin) or amphetamine (e.g., Adderall, Evekeo, Dexedrine) — compared to the general population.
These are the preliminary study findings published this week by a team of researchers from the University of Utah Health, which is quick to point out that its data does not indicate that ADHD medications cause Parkinson’s disease. The absolute risk of developing Parkinson’s, even for those treated with ADHD medication, remains very low – only eight or nine people in 100,000.
The study1, published in Neuropsychopharmacology, retrospectively examined medical records from the Utah Population Database (UPDB) of 31,769 patients with ADHD and 158,790 individuals without the condition. Of the ADHD sample, 2,716 were prescribed amphetamine salts, 1,941 were prescribed methylphenidate, and 303 received both medications. The included patients were Utah residents ages 20-60 who had no prior diagnosis of Parkinson’s or a similar disease.
The researchers controlled for some factors that increase risk of developing Parkinson’s including psychotic disorders, tobacco use, and a history of drug/alcohol abuse. They were unable to control for other risk factors including head trauma, brain injury, or environmental toxins.
The reason for the increased risk among patients with ADHD is unclear. Additional research is needed to determine the root cause of the association between ADHD and Parkinson’s — both disorders that impact the central nervous system and release of dopamine in the brain. Some posit that the true association is between Parkinson’s and severity of ADHD, not necessarily ADHD medication and progressive nervous system disorders. Meaning, people with more severe ADHD may be more likely to take medication to manage symptoms, and more likely to develop degenerative neurological diseases — even if they did not use medication to manage symptoms. These theories must be tested in further research.
This study received funding from the National Institute on Drug Abuse.
1Karen Curtin, Annette E. Fleckenstein, Brooks R. Keeshin, et al. “Increased risk of diseases of the basal ganglia and cerebellum in patients with a history of attention-deficit/hyperactivity disorder.” Neuropsychopharmacology, 12 September 2018. doi: 10.1038/s41386-018-0207-5