Exclusion of psychiatric disorders in neuropathic pain research: a secondary analysis of 312 randomized controlled trials.

Abstract

Chronic neuropathic pain frequently coincides with psychiatric disorders. Randomized controlled trials (RCTs), which underpin treatment guidelines, often seek to reduce confounding variables through exclusion criteria. This may affect the representation of populations with psychiatric comorbidities. This secondary analysis of 312 RCTs on neuropathic pain interventions examined how psychiatric-related exclusions are reported. Data were drawn from a published systematic review of neuropathic pain interventions. We identified 312 unique RCTs, and 2 independent reviewers coded psychiatric-related inclusion and exclusion criteria with 93% agreement. Frequencies of definite and probable psychiatric exclusions were described, and reporting of methods used to determine eligibility was assessed. Across 312 studies, 60% reported definite psychiatric exclusion criteria, 55% probable criteria, and 80% reported either or both. Substance-related disorders (38%) and depression (22%) were the most frequently specified exclusions. Among studies with definite psychiatric exclusions, 19% described the process by which eligibility was determined. Psychiatric-related exclusions are common across neuropathic pain RCTs. This may influence the generalizability of findings to individuals with comorbid psychiatric conditions, a substantial subgroup of the neuropathic pain population. The exclusion of participants with depression is notable given its frequent co-occurrence with neuropathic pain. Future research may benefit from greater transparency in reporting and continued consideration of how exclusion criteria balance methodological rigour with applicability to real-world clinical populations.