The study provides one of the clearest indications to date that a widely used ADHD medication does not increase long-term psychosis risk - and may even offer some protection when used early in life.
A major new study has found that commonly prescribed medication for attention deficit hyperactivity disorder (ADHD) in childhood may not only be safe in the long term, but could also lower the risk of developing serious psychotic disorders later in life.
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The research, led by scientists at University College Dublin and the University of Edinburgh, challenges longstanding concerns that stimulant medications might increase the risk of conditions such as schizophrenia.
ADHD is one of the most common mental disorders, affecting an estimated 8 percent of children and teenagers. Worldwide, around 366 million adults have ADHD, with symptoms including trouble focusing, restlessness, and impulsivity.
No evidence of increased psychosis risk
The study, published in JAMA Psychiatry, analysed health data from nearly 700,000 people born in Finland, including close to 4,000 people diagnosed with ADHD.
Researchers found no evidence that treatment with methylphenidate - the most commonly prescribed ADHD medication for children - increased the likelihood of developing psychotic disorders in adulthood.
"We know that when children with ADHD are followed into adulthood, a small but significant minority develop psychotic disorders such as schizophrenia," said Professor Ian Kelleher, a professor of Child and Adolescent Psychiatry at the University of Edinburgh and the study’s lead researcher.
"A critical question has been whether ADHD medication causes that risk, or whether this is a case where correlation does not equal causation. Our findings suggest the medication itself is not driving that risk," he explained.
The question has been a key concern in psychiatric research for years, particularly given that stimulant medications act on dopamine, a brain chemical also implicated in psychosis.
"A number of studies have shown that a small but significant minority of children with ADHD go on to develop psychotic disorders – in our study about 6 percent did,” Kelleher told Euronews Health.
"That has raised concerns about whether ADHD medication could be contributing to that risk, especially since stimulant medications increase the activity of a brain chemical called dopamine, which is also implicated in psychosis."
A possible protective effect in younger children
While the main finding showed no increased risk, researchers also identified a potential additional benefit - children treated with methylphenidate before the age of 13 showed a slightly lower risk of developing psychosis later in life.
"The fact that early treatment was associated with a lower long-term risk of psychosis suggests these medications may do more than manage symptoms in childhood - they may also have longer-term protective effects against severe mental illness, though this requires further research," Kelleher said.
He added that the overall findings should be "reassuring for doctors, patients and assure families considering treatment" and that "at normal licensed doses, methylphenidate treatment does not seem to increase your risk of psychosis".
Further research needed
But the results of the study apply specifically to methylphenidate and to children and adolescents.
“We were only able to look at methylphenidate," Kelleher said.
"We were unable, however, to look at another major class of stimulant medications used to treat ADHD, called amphetamines. So we cannot draw any conclusions about the risk of psychosis for amphetamine-type medications," he told Euronews Health.
The study also does not address the growing number of adults being diagnosed with ADHD.
"As more and more adults are being diagnosed with and treated for ADHD, we do not know whether our findings would also hold true for adults," Kelleher said.
"There’s also important further work to be done to understand why psychosis risk is elevated in children with ADHD, even though this increased risk isn’t explained by methylphenidate treatment," he added.
