A large multinational study led by researchers at Aston University has found that people with ADHD face their highest risk of self-harm in the three months before starting medication, not after treatment begins. The findings, drawn from more than 460,000 patients across five healthcare systems, challenge long-standing fears that ADHD drugs themselves drive self-harm.
What the research examined
The study, published in BMJ Mental Health, used a self-controlled case series design, meaning each patient's own data across different time periods served as the comparison, rather than comparing separate groups of medicated and unmedicated people. This approach, researchers say, reduces the risk of confounding from underlying differences in health status between patients who do and do not take medication.
Researchers compared three windows: the 90 days before treatment started, the first 90 days of medication use, and the period afterward. Data came from Hong Kong, New Zealand, South Korea, Taiwan and the United Kingdom, covering individuals who began ADHD medication and had a recorded instance of self-harm between 2001 and 2020. The project involved institutions including UCL, the University of Hong Kong, the University of Auckland, Sungkyunkwan University, National Cheng Kung University, and several other partner universities across Asia, Australia, Europe and North America.
A consistent pattern across five systems
In every healthcare system studied, self-harm risk was highest in the 90 days immediately preceding treatment and declined, though remained somewhat elevated, after medication began. Dr Adrienne Chan, a pharmacy lecturer who led the study, said the findings point to an overlooked window for intervention. "Many people are already at their highest risk before treatment even begins," she said, adding that recognizing this period "could help us provide support earlier, when it may make the greatest difference."
Regius Professor Ian Wong, also of Aston Pharmacy School, said the collaboration demonstrates how data can be shared responsibly across borders. "We are committed to using big data not simply to answer scientific questions, but to generate evidence that helps clinicians, informs policy, and ultimately benefits patients," he said, noting that patient-level data remained secured within each participating country.
What the findings do and do not show
As an observational analysis rather than a randomized trial, the study can describe when risk is highest but cannot fully explain the underlying biological or psychological mechanisms. The researchers suggest that worsening, untreated symptoms in the lead-up to diagnosis and treatment may contribute to heightened vulnerability, though this interpretation is not definitively proven by the data alone.
The team plans further research into what happens when patients stop or restart medication, and whether factors such as ethnicity or socioeconomic status affect access to care and outcomes. For now, the researchers say the clearest practical lesson is that clinical monitoring and support should be concentrated in the period before treatment starts, rather than withheld out of concern about the medication itself.