The results published by Man and colleagues  (open-access) sit right with me. I say that on the basis that previous research suggesting that attention-deficit hyperactivity disorder (ADHD) may 'prime' someone for an elevated risk of developing psychosis (see here) has potentially received some welcome substantiation. That MPH might not be the bogeyman that some people might think (see here too) is also an important part of the Man findings (minus any charges of me providing medical or clinical advice on this blog... I'm not).
The Man paper is open-access but a few choice details are worthwhile mentioning:
- Based on data from the "Clinical Data Analysis and Reporting System (CDARS)" an initiative based in Hong Kong, researchers set about identifying those "aged 6–19 years who received at least one prescription of MPH with at least one psychotic disorder and/or hallucination diagnostic code (psychotic events) during the study period (January 2001 to December 2014)." Given that only MPH and atomoxetine are seemingly licensed in the Hong Kong for "the treatment of ADHD", the authors were able to focus specifically on MPH quite easily.
- Although over 20,000 patients were in receipt of MPH prescriptions, only data for 103 participants were used in the study as a result of that diagnosis of a psychotic/hallucinatory condition. Most were male and 76 out of the 103 participants had "a clinical ADHD diagnosis."
- Researchers looked at MPH treatment and those psychotic/hallucinatory events taking into the account timing and including "a 90-day pre-exposure period" representing a period before MPH use (see here).
- Results: "The primary analysis indicated no statistically significant association between MPH treatment and occurrence of incident psychotic events." But, when compared with baseline data, there did seem to be something to see during that pre-exposure period (before MPH) and incident psychotic event(s). Ergo, something other than MPH use seemed to be linked to the experience of psychosis and we therefore head back to the idea that ADHD as one reason for MPH use might have some quite profound implications for future mental health.
There is still quite a bit more to do in this area as per more longitudinal research with greater participant numbers. I might also draw your attention to Table 2 of the Man paper (see here) examining other 'psychiatric comorbidities' when it came to those participants experiencing a psychotic episode. The list of potential correlates is interesting in light of other work (see here).
Whilst MPH comes out of such research with more than a whiff of roses, it is perhaps important to understand that medicines, all medicines come with potential side-effects and that includes MPH. Nevertheless, the idea that the benefits of controlled use of MPH might trump the risk of serious psychiatric side-effects such as psychosis is something that needs to be said and with it, a realisation that treating/managing the signs and symptoms of ADHD early, might have more profound repercussions for those diagnosed...
 Man KKC. et al. Methylphenidate and the risk of psychotic disorders and hallucinations in children and adolescents in a large health system. Translational Psychiatry. 2016; 6: e956.