Intellectual Disability and Psychiatric Disorders as Exclusion Criteria in Randomized Controlled Trials (RCT)

People with intellectual disability or psychiatric disorders are commonly excluded from Randomized Controlled Trials (RCTs) because of explicit exclusion to the trials or because of inaccessible research protocols. We analyzed the exclusion rate of persons with cognitive impairment, psychiatric disorders and inability to give informed consent in interventional RCTs about the first 10 causes of global DALYs (disability- adjusted life-years) according to the Global Burden of Disease Study (GBD) utilizing the website Clinicaltrials.gov. A total of 2809 studies in the 10 selected categories were reviewed. "Cognitive impairment" was present in 488 (17.4%) studies, "Behavioural and psychiatric disorders" was present in 616 (21.9%) studies, "Inability to grant informed consent" was present in 498 (17.7%) studies and the three explicit criteria were present, alone or in combination, in 1076 studies (38.3%). Other disability-related exclusion criteria were considered to be implicit exclusion criteria and were present in 1233 (43.9%) studies. A judgement was made on the correlation between the exclusion criteria and the primary objectives of the studies analyzed. The low level of representation of people with disabilities in RCTs, in addition to being an ethical problem, is a limitation of scientific knowledge because it considerably reduces the external validity of a significant part of medical research. There is a need to review the way scientific research designs are constructed, seeking to promote greater inclusiveness of people with disabilities.