ADHD medication linked with higher risk for Parkinson’s disease
Patients with ADHD who were treated with amphetamine- or methylphenidate-based medications may be at higher risk for basal ganglia and cerebellum disorders such as Parkinson’s disease, secondary parkinsonism or essential tremor later in life, according to findings recently published in Neuropsychopharmacology.
“Little is known about the effects of long-term, therapeutic use of psychostimulants such as that associated with treatment of ADHD,” researchers wrote.
They looked at data from 31,769 patients diagnosed with ADHD, of whom 4,960 had been prescribed mixed amphetamine salts (n = 2,716), methylphenidate (n= 1,941), or both (n = 303). These patients were then matched with 158,790 patients without ADHD.
Researchers found all patients with ADHD had a 2.4-fold increased risk for Parkinson’s disease, secondary parkinsonism or essential tremor vs. the patients without ADHD after controlling for age, sex, psychotic conditions and tobacco use. In addition, the 4,960 patients with ADHD who had been prescribed amphetamine- or methylphenidate-based psychostimulants had an 8.6-fold increased risk for Parkinson’s disease, secondary parkinsonism or essential tremor.
“Because ADHD was not widely acknowledged as a psychiatric diagnosis until DSM-II in 1968 and is usually identified in children, our ability to assess a linkage between ADHD and [basal ganglia and cerebellum] diseases (typically diagnosed in older adults) was limited to those who developed onset of these neurological conditions before age 60,” researchers wrote.
“Our calculations likely underestimate the total impact of ADHD on the risk for developing [basal ganglia and cerebellum] diseases, especially in younger populations,” they added.
There is not enough scientific evidence yet to suggest whether the ADHD medications, the disorder itself, or a combination of the two led to their findings, according to study co-author Glen R. Hanson, DDS, PhD, vice-dean of the School of Dentistry at the University of Utah.
“Amphetamines do alter, and in high doses can damage, the pathway that is involved in Parkinson’s disease and ADHD, so there certainly seems to be a pharmacology component,” he told Healio Family Medicine.
“However, we don’t have enough data yet to say if those with mild cases of ADHD develop mild forms of Parkinson’s, or if those who have severe forms of ADHD develop severe forms of Parkinson’s, so it’s hard to conclusively say either way if it’s the disease or the medications that heightens the risk,” Hanson added.
Until an answer to this question can be found, he suggested primary care physicians use the findings in tandem with parental observations and proven assessments regarding ADHD to carefully consider the medications that they prescribe patients with ADHD.
“PCPs should not prescribe drugs for ADHD simply because they are convenient and we think the child has ADHD based on a few casual observations by the parents,” Hanson said in the interview. “We want to prescribe drugs for ADHD because we see from performing assessments that there’s a genuine need for the child to be on these medications.”
He said that he believed their findings are the first of their kind, and offered suggestions for ways to build on their results.
“I’m not aware of a previous study that has shown a link between a pediatric psychiatric disorder and a geriatric neurological one. We now need to look for a mechanism that can prevent the progression from one disease to the next,” Hanson said in the interview. – by Janel Miller
Disclosures: The authors report no relevant financial disclosures.