No drug comes without its side effects. A study out today, however, should comfort anyone worried about the long-term consequences of taking methylphenidate, the active ingredient in brand-name drugs like Ritalin, for their attention deficit hyperactivity disorder.
Scientists in the UK studied the mental health outcomes of people diagnosed with ADHD in Finland. Though people with ADHD were more likely to develop psychotic disorders later in life compared to people without ADHD, they found no evidence that methylphenidate itself raised this risk. Though more research on other ADHD medications is warranted, the findings seem to dispel a common fear about taking Ritalin for too long, the researchers say.
“That’s reassuring for doctors, patients, and families when it comes to deciding whether to have stimulant treatment,” study author Ian Kelleher, a professor of child and adolescent psychiatry at the University of Edinburgh, told Gizmodo.
An uncertain risk
Several studies have shown that a small but noticeable percentage of children diagnosed with ADHD will go on to develop psychotic disorders like schizophrenia as adults. It’s also known that abusing stimulants can cause similar issues. Since stimulants are a common treatment for ADHD, that’s led to concern that even the therapeutic use of these drugs in smaller doses could be responsible for the added risk seen in these children.
It would be unethical to conduct the sort of randomized, controlled trials that could clearly investigate whether such a link is genuine, according to Kelleher (among other things, it would require giving some children an ineffective placebo for a prolonged period). That said, there still are quasi-experimental approaches that can help answer this question.
In this latest study, the researchers tracked the long-term health of roughly 700,000 people born in Finland, including nearly 4,000 children and teens diagnosed with ADHD. Because prescribing practices for ADHD vary between different hospital districts, the researchers could compare the rate of psychotic disorders among those who were given methylphenidate for their ADHD and those who weren’t.
“We can harness this variation to create, essentially, a natural experiment to tease out whether stimulants are causing psychosis or not,” said Kelleher, who is also an adjunct professor in the School of Medicine at University College Dublin.
Overall, about 6% of people with ADHD in the study were later diagnosed with a psychotic disorder by age 30, a higher rate than usual. But the long-term use of methylphenidate wasn’t associated with any higher risk. Interestingly, the researchers even found some evidence that methylphenidate can slightly lower the risk of later psychosis, though this lower risk was only seen in children who began taking the drug before the age of 13.
Some research in animals has suggested that early exposure to methylphenidate might cause long-lasting changes in how our brain’s dopamine system develops, which might help “normalize” disordered aspects that could raise psychosis risk. At the same time, Kelleher notes this possible protective effect was small and could just be a chance finding.
“But our main finding, that there was no overall increased risk of psychosis in children and adolescents treated with methylphenidate, is robust and reassuring,” he added.
The team’s findings were published Wednesday in JAMA Psychiatry.
Other areas of research still needed
Methylphenidate is the most commonly prescribed stimulant treatment for ADHD, but it’s not the only one. So these results can’t rule out that the other major class of ADHD drugs, amphetamines like Adderall, could still increase psychosis risk.
It’s also unknown whether there are any different risks in people who start taking stimulants for their ADHD as adults—an especially relevant question since the rate of new adult cases in the U.S. and other countries has risen greatly in just the past few years.
Kelleher and his team hope to investigate both of these questions in similar future studies.
