A major new study, led by scientists at University College Dublin and the University of Edinburgh and funded by the St John of God Research Foundation, has found that commonly prescribed attention deficit hyperactivity disorder (ADHD) medication in childhood may lower the long‑term risk of developing serious psychotic disorders, including schizophrenia.
Treatment with methylphenidate, the most commonly prescribed ADHD medication for children, before the age of 13 was shown to be associated with a reduced risk of psychosis in adulthood.
At a time when diagnoses of ADHD are rising rapidly worldwide, concerns about whether stimulant medications might increase the risk of psychosis have fuelled public anxiety among parents, clinicians and policymakers. This new evidence directly challenges that narrative.
No increased risk — and a possible protective effect
Focusing on nearly 4,000 young people diagnosed with ADHD, the researchers found no evidence that treatment with methylphenidate, the most commonly prescribed ADHD medication for children, increased the likelihood of developing a psychotic disorder later in life.
"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, 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."
Reassurance for families and clinicians
The researchers found no evidence that treatment with methylphenidate increased the likelihood of developing a psychotic disorder later in life.
The results are likely to offer reassurance to families weighing up treatment decisions and to clinicians concerned about long term safety.
The study, published in JAMA Psychiatry, used advanced statistical methods to examine how natural differences in ADHD prescribing practices across Finnish hospital districts influenced later psychosis risk.
Analysing health data from almost 700,000 people born in Finland, the scale of the study makes it one of the most comprehensive investigations to date into the long term mental health outcomes associated with ADHD treatment.
"Overall, these findings are reassuring," Professor Kelleher added.
"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."
The authors stress that the apparent protective effect was seen only in those treated during childhood.
The same benefit was not observed among individuals diagnosed and treated during adolescence or adulthood.
Growing urgency as adult ADHD diagnoses surge
Dr Colm Healy, Research Fellow at University College Dublin and lead author of the study, said the findings highlight the need for age‑specific research as adult ADHD diagnoses continue to increase.
"There are important developmental differences between the childhood brain and the teenage or adult brain. "We can't assume that the effects of stimulant medication will be the same across different stages of life. Given the rapid rise in adult ADHD treatment, understanding these differences is now an urgent priority."
The researchers say the findings underline the importance of early diagnosis, careful clinical assessment and evidence‑based treatment, and provide a timely counterpoint to fears surrounding ADHD medication.
