Predictors of treatment outcome in adults with ADHD treated with OROS® methylphenidate

Background: We conducted a post-hoc analysis of the Long-Acting MethylpheniDate in Adult attention-deficit hyperactivity disorder (LAMDA) study to investigate predictors of response in adults with ADHD randomly assigned to Osmotic Release Oral System (OROS)®-methylphenidate hydrochloride (MPH) 18, 36 or 72mg or placebo. Methods: LAMDA comprised a 5-week, double-blind (DB) period, followed by a 7-week, open-label (OL) period. A post-hoc analysis of covariance and a logistic regression analysis were undertaken to detect whether specific baseline parameters or overall treatment compliance during the double-blind phase contributed to response. The initial model included all covariates as independent variables; a backward stepwise selection method was used, with stay criteria of p< 0.10. Six outcomes were considered: change from baseline CAARS:O-SV (physician-rated) and CAARS:S-S (self-report) scores at DB and OL end points, and response rate (≥ 30% decrease in CAARS:O-SV score from baseline) and normalization of CAARS:O-SV score at DB end point. Results: Taking into account a significant effect of OROS®-MPH treatment versus placebo in the original analysis (p≤0.015), across the outcomes considered in this post-hoc analysis, higher baseline CAARS scores were most strongly predictive of superior outcomes. Male gender and lower academic achievement were also predictive for improved results with certain outcomes. Conclusions: Several baseline factors may help to predict better treatment outcomes in adults receiving OROS®-MPH; however, further research is required to confirm these findings and examine their neurobiological underpinnings. © 2010.