PARIS (FRONTLINE MEDICAL NEWS) – The use of attention-deficit/hyperactivity disorder medications is not associated with increased risk of epileptic seizures in patients with both disorders, according to an analysis of Swedish national registry data.

“Seizure history should not exempt patients from ADHD medication treatment,” Isabell Brikell stated at the annual congress of the European College of Neuropsychopharmacology.

This conclusion, based upon her study of 38,247 Swedes with epilepsy, including 4,418 with ADHD, runs counter to the boldface warning contained in product labeling for all ADHD medications.

“That’s why it’s such an important question, whether ADHD medications increase the risk of seizures,” observed Ms. Brikell, a PhD candidate in psychiatric genetics and epidemiology at the Karolinska Institute in Stockholm.

Swedish health care registries are famously comprehensive. For example, the Swedish prescription medication registry that Ms. Brikell and her coinvestigators tapped into for their ADHD/epilepsy study contains information on 99% of all prescriptions ordered in the country since 2005.

She reported on 38,247 Swedish patients with epilepsy born during 1976-2008 and followed during 2006-2013. Forty-eight percent were female. They collectively experienced 30,093 acute epileptic seizures of sufficient severity that they presented to a hospital for an unplanned visit. When the investigators compared the rate of seizures while the patients with ADHD were on a collective 4,248 ADHD medication exposure periods to that of epilepsy patients without ADHD, they found that the seizure risk was actually 17% lower in ADHD patients while on medication. This difference fell just shy of statistical significance. The analysis was adjusted for gender, age, and time on ADHD medications.

However, Ms. Brikell and her coworkers also performed a separate analysis for each individual with ADHD in which they compared seizure rates when a given patient was on ADHD medication versus off medication, a design that controls for many of the potential confounding factors that can occur with observational data. The seizure risk proved to be 19% lower while an individual was on ADHD medication – and this difference was indeed statistically significant.

In an interview, Ms. Brikell noted that the Swedish data are confirmed by a much larger National Institute of Mental Health–sponsored American study she was involved with that is now under review for publication. The U.S. study, which used the enormous MarketScan private health insurance database, demonstrated with the power provided by very large patient numbers that the seizure risk was convincingly lower while dual-diagnosis patients were on ADHD medication than when they were off.

“It’s reassuring to see the same effect across two countries with such different health care systems,” she commented.

Epilepsy is known to be inherently associated with a threefold increased prevalence of ADHD.

Ms. Brikell’s study was funded by the Swedish Research Council, the U.S. National Institute of Mental Health, and the Swedish Initiative for Research on Microdata in the Social and Medical Sciences. She reported having no financial conflicts of interest.


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