Health outcomes associated with crack-cocaine use: Systematic review and meta-analyses

Background: Crack-cocaine use is prevalent largely in socio-economically marginalized populations in the Americas. Its use has been associated with diverse health outcomes, yet no recent or systematic reviews of these exist. Methods: A systematic review of health outcomes associated with crack-cocaine use was performed, using MEDLINE, Scopus, Web of Science, CINAHL, PsycINFO, and LILACS up to October 2016. Search terms included crack-cocaine and health outcome-related keywords, targeting peer-reviewed studies on quantified health outcomes associated with crack-cocaine use. Random effects meta-analyses produced pooled odds ratios. Levels of evidence for major results were assessed using the GRADE approach. A review protocol was registered with PROSPERO (CRD42016035486). Results: Of 4700 articles returned, 302 met eligibility criteria, reporting on health outcomes for 14 of 22 ICD-10 chapters. Conclusive evidence and meta -analyses showed positive associations between crack-cocaine use and blood/sexually transmitted diseases (HIV and hepatitis C virus, others); moderate evidence and meta -analyses supported associations with neonatal health, and violence. There were mixed associations for mental and other health outcomes, yet insufficient evidence to perform meta -analyses for many categories (e.g., mortality). Most underlying research was of limited or poor quality, with crack-cocaine commonly assessed as a secondary covariate. Conclusions: Crack-cocaine use was associated with a range of health outcomes, although it was unclear if there was direct causal impact, interactions between risk factors, or external drivers of both crack-cocaine use and outcomes. Rigorous epidemiological studies are needed to systematically assess health outcomes of crack-cocaine use and underlying pathways, also to inform evidence-based interventions.