The Cochrane Collaboration withdraws a review on methylphenidate for adults with attention deficit hyperactivity disorder.

A Cochrane systematic review on immediate-release methylphenidate for adults with attention deficit hyperactivity disorder (ADHD) was withdrawn from the Cochrane Library on 26 May 2016 after substantial criticism of its methods and flawed conclusions. Retraction of scientific papers on this basis is unusual but can be necessary. We provide a summary of the criticism that led to the withdrawal. We detail the methodological flaws of the withdrawn Cochrane systematic review and general issues of bias and shortcomings of the included ADHD trials: cross-over designs compared with parallel-group designs, exclusion of participants with psychiatric comorbidity, absence of 'functional outcomes' and use of clinical outcomes with limited relevance, short trial duration and small trial populations, broken blinding caused by easily recognisable side effects, combining outcome assessments by trial investigators and participants, outcome reporting bias, poor evaluation of cardiovascular and psychiatric harms and conflicts of interest of trialists and systematic reviewers. The withdrawal of the Cochrane systematic review signals recognition of previous unreliable clinical ADHD research. We conclude that clinical trials of immediate-release methylphenidate in adults with ADHD are of very low quality. We urgently need well-conducted long-term trials free of bias to assess the benefits and harms of central stimulant treatment in adult ADHD.