Background and Aims Drug checking services provide people who use drugs with chemical analysis results of their drug samples while simultaneously monitoring the unregulated drug market. We sought to identify and synthesize literature on the following domains: (a) the influence of drug checking services on the behaviour of people who use drugs; (b) monitoring of drug markets by drug checking services; and (c) outcomes related to models of drug checking services. Methods Systematic review. A systematic literature search was conducted in MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, PsycINFO, Scopus, Web of Science and Dissertations and Theses Global. Eligible studies were peer‐reviewed articles and conference abstracts or grey literature, published in any language since 1990 and including original data on the domains. We assessed risk of bias for quantitative peer‐reviewed articles reporting on behaviour or models of drug checking services using National Institutes of Health tools. Results We screened 2463 titles and abstracts and 156 full texts, with 90 studies meeting inclusion criteria. Most (n = 65, 72.2%) were from Europe and used cross‐sectional designs (n = 79, 87.7%). Monitoring of drug markets by drug checking services (n = 63, 70%) was the most reported domain, followed by the influence of drug checking services on behaviour (n = 31, 34.4%), including intent to use, actual use and disposal of the drug, and outcomes related to models of drug checking services (n = 17, 18.9%). The most common outcome measures were detection of unexpected substances (n = 50, 55.6%), expected substances (n = 44, 48.9%), new psychoactive substances (n = 40, 44.4%) and drugs of concern (n = 32, 36.5%) by drug checking services. Conclusions Drug checking services appear to influence behavioural intentions and the behaviour of people who use drugs, particularly when results from drug checking services are unexpected or drugs of concern. Monitoring of drug markets by drug checking services is well established in Europe, and increasingly in North America. Concerns about drug contents and negative health consequences facilitate the use of drug checking services; lack of concern; trust in drug sellers; lack of accessibility of drug checking services; and legal and privacy concerns are barriers to use.

THIS PREPRINT HAS BEEN UPDATED AND FORMALLY PUBLISHED IN _ADDICTION_ [https://onlinelibrary.wiley.com/doi/10.1111/add.15734] (HTTPS://DOI.ORG/10.1111/ADD.15734 [https://doi.org/10.1111/add.15734]). A ONE-PAGE FACT SHEET [https://cdpe.org/publication/drug-checking-services-for-people-who-use-drugs-a-systematic-review/] IS ALSO AVAILABLE. BACKGROUND AND AIMS: Drug checking services (DCS) provide people who use drugs (PWUD) with chemical analysis results of their drug samples, while simultaneously monitoring the unregulated drug market. We sought to identify and synthesize literature on the following domains: (a) influence of DCS on behaviour of PWUD; (b) monitoring of drug markets by DCS; and (c) outcomes related to models of DCS. METHODS: This review followed PRISMA guidelines and was pre-registered in PROSPERO (CRD42018105366). A systematic literature search was conducted in MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, PsycINFO, Scopus, Web of Science, and Dissertations & Theses Global. Eligible studies were peer-reviewed articles and conference abstracts, or grey literature, published in any language since 1990 and including original data on the domains. We assessed risk of bias for quantitative peer-reviewed articles reporting on behaviour or models of DCS using National Institutes of Health tools. RESULTS: We screened 2,463 titles and abstracts and 156 full-texts, with 90 studies meeting inclusion criteria. Most (n=65, 72.2%) were from Europe and used cross-sectional designs (n=79, 87.7%). Monitoring of drug markets by DCS (n=63, 70%) was most commonly reported, followed by influence of DCS on behaviour (n=31, 34.4%) and outcomes related to models of DCS (n=17, 18.9%). The most common outcome measures were detection of unexpected substances (n=50, 55.6%), expected substances (n=44, 48.9%), new psychoactive substances_ _(n=40, 44.4%), and drugs of concern (n=32, 36.5%) by DCS. CONCLUSIONS: Monitoring of drug markets by DCS is well established in Europe and increasingly in North America. There is an emerging evidence base demonstrating the capacity of DCS to influence behavioural intention, and a smaller subset of findings on its impact on the enacted behaviour of PWUD. Further research is needed on enacted behaviours and corresponding health outcomes including overdose, particularly among people who inject drugs or use opioids.

Background: Due to the inherent subjectivity of pain, it is difficult to make accurate judgements of pain in others. Research has found discrepancies between the ways in which perceived "objective" (e.g., medical evidence of injury) and "subjective" information (e.g., self-report) influence judgements of pain. This study aims to explore which potential cues (depictions of sensory input, brain activation, self-reported pain and facial expressions) participants are most influenced by when evaluating pain in others. Methods: First, 60 participants (23 women, 36 ± 10 years old) judged who was in more pain between two different pain indicators representing two different patients. These trials revealed which congruent indicator (i.e., two high pain indicators) would most influence participant decisions. Second, participants prescribed quantities of analgesia for one patient's pain based on two different pain indicators. These trials revealed which incongruent indicators (i.e., one high and one low indicator) would most influence participant decisions.Results: As predicted, facial expressions were perceived as subjective and were the least likely, among all pain indicators, to influence observer's judgements of pain. Participants relied upon indicators they perceived as objective. Self-report pain ratings had the greatest influence on participants judgements about how much analgesic cream to prescribe and was perceived as objective by half of the participants. Conclusions:We found that in situations where incongruent information was presented about an individual's pain, participants relied on pain indicators that they perceived to be objective. The current study provides important insights about biases that people hold when making judgements of pain in others.Significance: Interpretation and assessment of pain remains one of the largest barriers to pain management and involves complex, idiosyncratic processing.This study provides insights into what information participants view as critical in making attributions of pain when presented with multiple, seemingly incongruent sources of information.

BACKGROUND AND AIMS: Drug checking services (DCS) provide people who use drugs (PWUD) with chemical analysis results of their drug samples, while simultaneously monitoring the unregulated drug market. We sought to identify and synthesize literature on the following domains: (a) influence of DCS on behaviour of PWUD; (b) monitoring of drug markets by DCS; and (c) outcomes related to models of DCS. METHODS: This review followed PRISMA guidelines and was pre-registered in PROSPERO (CRD42018105366). A systematic literature search was conducted in MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, PsycINFO, Scopus, Web of Science, and Dissertations & Theses Global. Eligible studies were peer-reviewed articles and conference abstracts, or grey literature, published in any language since 1990 and including original data on the domains. We assessed risk of bias for quantitative peer-reviewed articles reporting on behaviour or models of DCS using National Institutes of Health tools. RESULTS: We screened 2,463 titles and abstracts and 156 full-texts, with 90 studies meeting inclusion criteria. Most (n=65, 72.2%) were from Europe and used cross-sectional designs (n=79, 87.7%). Monitoring of drug markets by DCS (n=63, 70%) was most commonly reported, followed by influence of DCS on behaviour (n=31, 34.4%) and outcomes related to models of DCS (n=17, 18.9%). The most common outcome measures were detection of unexpected substances (n=50, 55.6%), expected substances (n=44, 48.9%), new psychoactive substances_ _(n=40, 44.4%), and drugs of concern (n=32, 36.5%) by DCS. CONCLUSIONS: Monitoring of drug markets by DCS is well established in Europe and increasingly in North America. There is an emerging evidence base demonstrating the capacity of DCS to influence behavioural intention, and a smaller subset of findings on its impact on the enacted behaviour of PWUD. Further research is needed on enacted behaviours and corresponding health outcomes including overdose, particularly among people who inject drugs or use opioids.

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