Childhood use of the stimulant methylphenidate, the most commonly prescribed medication for attention-deficit/hyperactivity disorder (ADHD), is not associated with increased risk for a psychotic disorder later on and may actually be protective in some patients, a new study suggested.

The registry cohort study showed that among patients with ADHD, those treated with methylphenidate (sold as Ritalin, Concerta, and other brand names) were no more likely to be diagnosed with psychosis than those who did not receive the medication.

In fact, treatment with the stimulant before age 13 was associated with a significant decreased risk for psychotic disorders, said investigators, who added that the findings should be reassuring to both clinicians and parents.

“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,” study investigator Ian Kelleher, MD, PhD, professor of child and adolescent psychiatry, University of Edinburgh, Edinburgh, Scotland, said in a press release.

The findings were published online on March 25, 2026, in JAMA Psychiatry.

Analytical Approach

Previous studies have suggested that children with ADHD have a slightly elevated risk for psychosis in adulthood, but it was unclear if stimulant use may play a causal role in this elevated risk.

To study the question further, researchers used instrumental variable analyses of data from multiple linked Finnish national registries, an analytical approach they said minimizes the risk for unmeasured confounding and allows for causal inference.

The cohort included all individuals born in Finland from 1987 to 1997 who were diagnosed with ADHD before age 18 and after January 1, 2003 (following methylphenidate licensing in the country). The sample included 678,546 without ADHD (50.66% male) and 3956 with ADHD (80.41% male).

In the ADHD cohort, the median age of diagnosis was 14.16 years, and 68.96% received methylphenidate within the first 4 years.

Participants were followed for a mean of 8.47 years, and the median age at the end of follow-up was 22.16 years. Using a total nationwide prospective birth cohort allowed for longer follow-up than is normally possible with randomized clinical trials, the authors noted.

Investigators assessed two psychosis outcomes in patients with childhood ADHD: nonaffective psychosis and schizophrenia.

‘Important’ Insight

During follow-up, those with ADHD were significantly more likely than individuals without the disorder to be diagnosed with nonaffective psychosis (5.71% vs 1.56%; odds ratio [OR], 3.83; P < .001) and schizophrenia (0.81% vs 0.34%; OR, 2.37; P < .001).

After adjusting for confounders, which included sex, education, age at diagnosis, and birth year, the analysis found no statistically significant evidence for an association between sustained treatment with methylphenidate (at 30 mg/d) and risk for psychosis.

However, the analyses uncovered evidence that sustained methylphenidate treatment was associated with a significantly lower risk for psychosis among children diagnosed with ADHD before age 13 at 3 years (risk difference [RD], -0.24; P = .03) and 4 years (RD, -0.21; P = .02). Although risk was also lower in this cohort at post-diagnosis years 1 and 2, the difference was not statistically significant.

There was no significant link between methylphenidate use and schizophrenia.

An insufficiently strong instrument precluded researchers from running the same analyses for patients diagnosed with ADHD after age 13.

While the analyses examined the effect of sustained methylphenidate treatment within defined intervention windows (1-4 years post-diagnosis), they did not account for treatment continuation or initiation after these windows.

“The mechanisms underlying a potentially reduced risk of psychosis in children treated for ADHD will require replication and further study, but these findings may provide important new insights for psychosis prediction and prevention,” researchers wrote.

Sensitive Developmental Window?

This finding “may point toward a sensitive developmental window in which methylphenidate could affect the trajectory of brain development,” wrote the authors, noting prior research on juvenile animals that demonstrated long-lasting effects of stimulant treatment on cerebral blood flow, including in dopamine-rich brain regions implicated in the development of psychosis.

Further research on psychosis risk among teens diagnosed with ADHD will be important, said the authors. They added that such research is also warranted in adults, given the rapidly increasing diagnoses and treatment of ADHD in this age group.

“There are important developmental differences between the childhood brain and the teenage or adult brain,” lead study author, Colm Healy, PhD, research fellow, University College Dublin, Dublin, Ireland, commented in the press release.

“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,” Healy said.

The study was funded by St John of God Research Foundation. Kelleher and Healy reported having no relevant conflicts of interest.