Registered clinical trials on addiction: a cross-sectional study on ClinicalTrials.gov

Objective Clinical trials drive the development of medicine. However, little is known about the current status of clinical trials on addiction. This study aimed to provide a comprehensive analysis of registered addiction-related trials from ClinicalTrials.gov. Methods We examined all addiction-related trials registered on ClinicalTrials.gov up to March 23, 2020. Statistical analysis was performed by using SPSS 25.0, and a two-sided p < .05 was considered statistically significant. Results 370 eligible trials were identified. Over half of trials were completed, while only 13.8% of trials reported results. Sample sizes varied a lot with a median number of 84 per trial. Universities were the primary sponsor for 164 (44.3%) trials, followed by hospitals (96, 26.0%). Compared to trials without results, more trials with results were sponsored by universities (62.7% vs. 41.4%, p = .003), and conducted in United States/Canada (90.2% vs. 48.3%, p < .001). Most interventional trials were randomized with a parallel assignment, and 56.3% were blinded. Thirty one (41.3%) observational trials were cohort studies and 12 (16.0%) were case-only studies. Interventional trials were more likely to be funded by the US Government, while more observational trials were supported by industries. Trials funded by the US Government were more likely to be completed than those funded by other sources (p = .009). Conclusion Most registered trials on ClinicalTrials.gov about addiction were interventional trials with purpose for treatment. Most interventional trials were randomized, parallel, and masked. Our analysis highlighted the need for improvement in completing study results on the ClinicalTrials.gov.