Harmen Beurmanjer

31 Review on the GHB using Population 2 difficult to detect and hidden, because most people use at home and there is a strong stigma towards GHB (Grund et al., 2015; Palamar & Halkitis, 2006). Another specific target population consists of gays and bisexual men using GHB in the context of chemsex: men having sex with men (MSM). Though they less frequently experience GHB-related comas, they more often have other health consequences related to GHB use, like sexually transmitted deceases (Evers et al., 2020; McCall, Adams, & Willis, 2015). Additional targeted prevention strategies might therefore best focus on the health issues specific for this population (Sewell et al., 2019). In line with the above, a personalized approach to prevent GHB related harm has been proposed (Grund et al., 2015). Individually tailored advice should preferably be based on a thorough assessment of GHB use and its context (Phan et al., 2020). In the Netherlands, several interventions have been suggested over the past years, such as a GHB-helpline and a ’G-app’ with information on monitoring and dosage, dosage syringes and timers, and an awareness campaign on risks of overdosing (Grund et al., 2015). This meets the need for non- didactic educational materials (Palamar & Halkitis, 2006). For patients with GUD referral to specialized care facilities is warranted, aiming to supervise detoxification attempts and prevent relapse. In case of opioid dependence substitution treatment is very common and thoroughly studied, however for patients with GUD no substitution treatment is yet available (Beurmanjer, Kamal, de Jong, Dijkstra, & Schellekens, 2018). The findings of this study have to be seen in light of some limitations, resulting in knowledge gaps and related recommendations for future studies. First, about half of the studies included less than a hundred subjects (45%), and the range between studies is large: between 7 (Boyce et al., 2000) and 1331 subjects (Anderson et al., 2006). We did not correct for these differences and this could have biased our results. A meta-analysis can be performed on predefined variables to solve this problem, however reported variables differ in definitions, completeness and accuracy, influencing valid comparisons between studies. For example, definitions for GHB dosage (variation in concentration), psychiatric problems (disorder or symptoms) and GHB dependence (frequency or severity of use) differ between studies. Another example is the description of comorbid substance use. Most, but not all, studies reported only the most commonly co-used drugs (Boyd et al., 2012; Dietze et al., 2008; Galicia et al., 2019; Galicia, Nogue, & Miro, 2011; Horyniak et al., 2013; Kapitany-Foveny et al., 2017; Liechti et al., 2006; Madah-Amiri, Myrmel, & Brattebo, 2017; Munir et al., 2008), or chose to report categories only. These differences affect the calculated numbers in this review and limit the possibility to integrate data and execute meta-analysis (Jager, Putnick, & Bornstein, 2017). Second, included studies mainly consisted of retrospective database/cohort studies, followed by surveys and case series. Many studies focused on a particular setting, e.g. at Emergency Departments (43%), and to a lesser extent at addiction care (15%). Only 20% of the studies recruited participants from the general population, mostly using convenience sampling. These different recruitment methods help provide an overview of different GHB