In a 16-year follow-up of the landmark MTA study, ADHD itself did not increase psychosis risk, but greater cannabis use was significantly associated with both screening positive and confirmed psychotic symptoms.
Parents of children with ADHD concerned about long-term mental health risks.
ADHD did not increase psychosis risk; cannabis use was significantly associated with psychotic symptoms (p < 0.01)
What the researchers found
Researchers followed 509 MTA study participants (childhood ADHD) and 276 age-matched controls for 16 years, assessing psychotic symptoms through young adulthood.
ADHD did not increase the risk for psychotic symptoms. The rates were essentially identical: 5% of ADHD participants and 4% of controls screened positive for at least one psychotic symptom (p = 0.60). Clinician-confirmed psychotic symptoms were rare and similar between groups (1.1% vs. 0.7%, p = 0.72). Most psychotic symptoms were transient.
However, across both groups, cannabis use emerged as a significant independent factor. Greater cannabis use was reported by those who screened positive for psychotic symptoms (p < 0.05) and those with clinician-confirmed psychotic symptoms (p < 0.01).
The findings support the recommendation that youth should not use cannabis, particularly given that ADHD youth already have higher rates of substance use.
Why it matters
Parents of children with ADHD have long worried about their children's vulnerability to serious mental illness. This 16-year study provides strong reassurance that ADHD itself does not increase psychosis risk. However, the cannabis-psychosis link adds urgency to addressing substance use in the ADHD population, where substance use rates are already elevated.
The numbers in context
509 ADHD participants, 276 controls at year 16. Psychosis screening: 5% ADHD vs. 4% controls (p = 0.60). Clinician-confirmed: 1.1% vs. 0.7% (p = 0.72). Cannabis use: significantly higher in screen-positive (p < 0.05) and confirmed-positive (p < 0.01) groups.
How the study worked
Longitudinal follow-up of the Multimodal Treatment Study of Children with ADHD (MTA), the largest and longest ADHD treatment study. Assessments at 6, 8, 10, 12, 14, and 16 years post-enrollment. Trained research assistants administered a psychosis screener; positive screens were evaluated by study clinicians. Original enrollment mean age: 8.5 years. Year 16 mean age: 25.1 years.
What this study cannot tell us
The MTA sample was originally treatment-seeking and not population-representative. Psychotic symptoms were screened and confirmed at specific assessment points, potentially missing episodes between visits. The study cannot determine whether cannabis caused the psychotic symptoms or whether shared vulnerability led to both cannabis use and psychosis.
How to read the evidence
Strong evidence from a 16-year prospective follow-up of the landmark MTA study with appropriate comparison group.
When this study was published
Published in 2017. 16-year follow-up data from the MTA study (original enrollment 1990s).
The bigger picture
The MTA study is one of the most influential longitudinal studies in child psychiatry. Its finding that ADHD does not predict psychosis is reassuring, but the cannabis signal is consistent with the broader cannabis-psychosis literature. For ADHD youth, who are at higher risk for substance use, this reinforces the importance of substance use prevention as part of ADHD management.
Questions still open
- Are ADHD stimulant medications protective against psychosis, potentially masking an ADHD-psychosis link? Does the ADHD-related impulsivity increase cannabis use, which then increases psychosis risk? Should ADHD treatment protocols include more aggressive substance use prevention?
Common questions
Does ADHD increase the risk of psychosis?
Should kids with ADHD be extra careful about cannabis?
Read the original research
Psychotic Symptoms in Attention-Deficit/Hyperactivity Disorder: An Analysis of the MTA Database.
Journal of the American Academy of Child and Adolescent Psychiatry, 56(4), 336-343
Citation
Vitiello, Benedetto; Perez Algorta, Guillermo; Arnold, L Eugene; Howard, Andrea L; Stehli, Annamarie; Molina, Brooke S G. (2017). Psychotic Symptoms in Attention-Deficit/Hyperactivity Disorder: An Analysis of the MTA Database.. Journal of the American Academy of Child and Adolescent Psychiatry, 56(4), 336-343. https://doi.org/10.1016/j.jaac.2017.01.016
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