Design, reporting, and research focus of neurology and psychiatry drug trials (2020–2023): a registry-based meta-epidemiological study using ClinicalTrials.gov and NLP

Abstract Background Clinical trial registries document trial design, funding, and results reporting, but heterogeneous and unstructured entries limit cross-trial comparison. Consequently, it is unclear how neurology and psychiatry drug trials are designed and reported in practice, hampering comparison of studies, understanding of the available evidence, and planning of future trials. The aim of this study was to quantify trial design features, results reporting practices, and research focus in neurology and psychiatry drug trials using harmonized registry data. Methods This is a registry-based observational study of interventional neurology and psychiatry drug trials registered on ClinicalTrials.gov between 2000 and 2023. Using natural language processing (NLP) with manual validation, we extracted and harmonized trial information on phase, randomization, masking, sample size, funding source, results reporting, and target diseases and drugs. We also performed content-based clustering and visualization to explore patterns across trials by drug and disease category. We analyzed temporal trends and differences across trial characteristics. Results We included 18,609 trials. Most were early phase, single-center, and small, typically enrolling 11–50 participants; 60% were completed. Industry funded 36% of trials, with a declining share over time and a corresponding increase in university sponsorship. Ten percent of trials were non-randomized and 38% were open label. Among trials completed after 2007, 50% reported results, with a mean delay of 12 months. The most frequently studied conditions were pain (10%), schizophrenia (8%), depression (8%), and Alzheimer’s disease (7%). Drug testing was widely distributed, with atypical antipsychotics, levodopa, and ketamine each accounting for 1–2% of trials. Content-based clustering identified disease-specific groupings of trials. Harmonized data are available through an interactive dashboard. Conclusions Registered neurology and psychiatry drug trials show persistent limitations in design and results reporting despite two decades of registry requirements. Registry-based analyses using computational harmonization can support empirical evaluation of trial practices and inform future trial design and reporting.