Summary: A large, national cohort study found that treating children diagnosed with ADHD using stimulant medication (methylphenidate) before age 13 was associated with a lower long-term risk of developing nonaffective psychotic disorders, including schizophrenia. The analysis of Finnish health records challenges the common concern that stimulant treatment increases later psychosis risk and instead suggests a possible protective effect when medication begins in childhood.
Key Facts
- Age matters: Reduced adult psychosis risk was linked specifically to starting methylphenidate treatment before age 13.
- Correlation vs. causation: Although some people with childhood ADHD later develop psychotic disorders, this study does not support the idea that stimulant medication causes that outcome.
- Developmental window: The apparent protective association was not seen for treatment begun in adolescence or adulthood, pointing to a possible critical period in early brain development.
- Scale and rigor: The investigation used national registry data from nearly 700,000 people born in Finland and applied instrumental variable methods to address regional prescribing variation and confounding.
Research overview
Researchers from University College Dublin and the University of Edinburgh, with funding from the St John of God Research Foundation, examined whether methylphenidate treatment for ADHD is linked to later risk of nonaffective psychotic disorders. Using comprehensive Finnish health registries covering people born between 1987 and 1997, the team applied advanced statistical techniques to estimate the relationship between prescribed methylphenidate and subsequent psychosis diagnoses.
With ADHD diagnoses rising globally, concerns have grown about stimulant medications and the risk of psychotic symptoms. The new study provides data that should reassure families and clinicians: the investigators found no evidence that appropriate, prescribed methylphenidate treatment raises the long-term risk of developing a psychotic disorder, and they observed a reduced risk when treatment began in childhood.
Key results
From the subgroup of 3,956 individuals diagnosed with ADHD (median age about 14 years), 69% had received methylphenidate at least once. Overall instrumental variable analyses indicated no clear association between sustained methylphenidate treatment and nonaffective psychosis across the whole ADHD sample. However, secondary analyses focusing on those diagnosed before age 13 showed a statistically significant reduction in risk after three and four years of cumulative treatment.
Professor Ian Kelleher, the study lead, noted that while a minority of people with childhood ADHD later develop psychotic disorders, the evidence does not point to ADHD medication as the cause. Instead, early treatment may influence developmental trajectories in a way that reduces long-term risk, although more research is required to confirm mechanisms and causality.
Implications for clinicians and families
The findings support careful, age‑appropriate clinical assessment and evidence‑based treatment planning. They offer reassurance that, when prescribed correctly, methylphenidate does not appear to increase the risk of later psychotic disorders and may even offer protective benefits if started in childhood. The authors emphasize that treatment decisions should remain individualized, balancing benefits, risks, and clinical context.
Key Questions Answered:
A: Short-term misuse or very high doses of stimulants can produce temporary symptoms in some individuals. This study focused on long-term outcomes following prescribed use and found no increased risk of developing a persistent psychotic disorder later in life among children treated appropriately with methylphenidate.
A: The researchers highlight developmental differences between the childhood brain and the adolescent or adult brain. Early intervention during a critical developmental window could influence neurodevelopmental pathways, whereas later treatment may not have the same long-term effect.
A: Not necessarily. The study supports the safety and potential long-term benefits of early, appropriate methylphenidate use, but clinicians should continue to perform careful assessments and consider behavioral, educational, and family factors alongside medication when making individualized treatment plans.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff.
About this psychosis and psychopharmacology research news
Author: David Kearns
Source: University College Dublin
Contact: David Kearns – University College Dublin
Image: The image is credited to Neuroscience News
Original Research: Open access. “Methylphenidate Treatment and Risk of Psychotic Disorder” by Colm Healy, Kirstie O’Hare, Ulla Lång, Johanna Metsälä, Anna Pulakka, Jane McGrath, Maria Migone, Dolores Keating, Liana Romaniuk, David Gyllenberg, Eero Kajantie, George Perrett, Jennifer Hill, Felix Elwert, and Ian Kelleher. JAMA Psychiatry. DOI: 10.1001/jamapsychiatry.2026.0152
Abstract
Methylphenidate Treatment and Risk of Psychotic Disorder
Importance
Methylphenidate is the primary pharmacological treatment for ADHD in childhood and adolescence. People with ADHD have an elevated risk of psychosis, but the long-term relationship between methylphenidate exposure and subsequent development of psychotic disorders has been unclear.
Objective
To estimate the association between methylphenidate treatment and the risk of nonaffective psychosis among children and adolescents diagnosed with ADHD.
Design, Setting, and Participants
This cohort study used instrumental variable analysis on linked national Finnish registry data for all individuals born from 1987 to 1997 (n = 697,289). Childhood and adolescent ADHD diagnoses (age <18 years) were identified from 2003 onward. Data were analyzed from June 2023 to December 2025.
Exposure
Cumulative methylphenidate treatment measured across four intervention windows (within 1, 2, 3, and 4 years after ADHD diagnosis). Average prescribing propensity within hospital districts served as instruments to account for regional differences in treatment practices.
Main Outcome and Measures
Diagnosis of nonaffective psychotic disorder (ICD-10 codes) by the end of follow-up (December 31, 2016). Instrumental variable analyses used two-stage least squares and the Anderson-Rubin test to estimate risk differences for each intervention window.
Results
In the ADHD sample (n = 3,956), 2,728 individuals (69.0%) received methylphenidate. Across the overall ADHD group, sustained treatment equivalent to 30 mg/day showed no significant association with nonaffective psychosis risk (1-year RD −0.14; 95% CI, −0.85 to 0.42; 4-year RD −0.15; 95% CI, −0.49 to 0.11). Secondary analyses among those diagnosed before age 13 indicated a reduced risk of psychosis at 3 and 4 years of treatment (3-year RD −0.24; 95% CI, −0.45 to −0.03; 4-year RD −0.21; 95% CI, −0.48 to −0.07).
Conclusions and Relevance
Using national Finnish registry data, this study found no overall link between sustained methylphenidate treatment and later nonaffective psychosis in individuals with ADHD. Secondary analyses suggest a potentially protective association for treatment begun in childhood. Additional research is needed to assess effects for those diagnosed and treated in adolescence or adulthood.