Patterns of drug use among people who inject drugs: A global systematic review and meta-analysis

Background: A better understanding of global patterns of drug use among people who inject drugs can inform interventions to reduce harms related to different use profiles. This review aimed to comprehensively present the geographical variation in drug consumption patterns among this population. Methods: Systematic searches of peer reviewed (PsycINFO, Medline, Embase) and grey literature published from 2008-2022 were conducted. Data on recent (past year) and lifetime drug use among people who inject drugs were included. Data were extracted on use of heroin, amphetamines, cocaine, benzodiazepines, cannabis, alcohol, and tobacco; where possible, estimates were disaggregated by route of administration (injecting, noninjecting, smoking). National estimates were generated and, where possible, regional, and global estimates were derived through meta-analysis. Results: Of 40,427 studies screened, 394 were included from 81 countries. Globally, an estimated 78.1 % (95 % CI:70.2-84.2) and 71.8 % (65.7-77.2) of people who inject drugs had recently used (via any route) and injected heroin, while an estimated 52.8 % (47.0-59.0) and 19.8 % (13.8-26.5) had recently used and injected amphetamines, respectively. Over 90 % reported recent tobacco use (93.5 % [90.8-95.3]) and recent alcohol use was 59.1 % (52.6-65.6). In Australasia recent heroin use was lowest (49.4 % [46.8-52.1]) while recent amphetamine injecting (64.0 % [60.8-67.1]) and recent use of cannabis (72.3 % [69.9-74.6]) were higher than in all other regions. Recent heroin use (86.1 % [78.3-91.4]) and non-injecting amphetamine use (43.3 % [38.4-48.3]) were highest in East and Southeast Asia. Recent amphetamine use (75.8 % [72.7-78.8]) and injecting heroin use (84.8 % (81.4-87.8) were highest in North America while non-injecting heroin use was highest in Western Europe (45.0 % [41.3-48.7]). Conclusion: There is considerable variation in types of drugs and routes of administration used among people who inject drugs. This variation needs to be considered in national and global treatment and harm reduction interventions to target the specific behaviours and harms associated with these regional profiles of use.