"Three studies evaluated cannabis use prevention interventions. Two studies evaluated school-based interventions and the third study evaluated two family-centred interventions and a web-based intervention.

"Four studies evaluated the cost-effectiveness of prescription opioid misuse prevention, three of which were conducted in the USA and one in South Korea. The interventions identified for the USA setting were a school-based programme, a family-centred programme and misuse-deterrent opioid formulations; a doctor's database assisting patient risk assessment was evaluated in the South Korean setting. All four studies utilised economic models to evaluate cost and benefit of intervention over 1- to 30-year time horizons.

"In this pilot pretest–posttest quasi-experimental study, we saw a lower proportion of SSP clients exclusively inject heroin and a higher proportion of SSP clients consume heroin through both injection and smoking after the implementation of a heroin pipe distribution program. The proportion of SSP clients who reported syringe reuse was also lower following the heroin pipe distribution intervention.

"People who use heroin (PWUH) have increased morbidity and mortality compared to the general population [1].

"Residential treatment is often considered the highest intensity of treatment for individuals with OUD [40], and may by particularly important for those with unstable housing, co-morbid mental health conditions, or high medical need [41].

"Growing evidence suggests that outpatient treatment, when coupled with MOUD, may be superior to other treatment settings.

"Methodology and Limitations

"The data available have limitations in respect to quality and coverage, however, the information available suggests that heroin was only present in the majority of overdose deaths in a relatively small number of EU countries. A significant share of overdose deaths was reported by Austria (67%), Italy (56%), Ireland (46% in 2017), Poland (44% in 2016) and Romania (43%).

"In 2021, the proportion of overdose deaths involving benzodiazepines increased in several countries and was present in more than half of the cases in Denmark, Austria, Portugal and Finland (see figure Proportion of drug-induced deaths with benzodiazepines involved in selected countries, 2019–2021 in Drug-induced deaths in Europe)."

"In 2022, generally very low levels of ketamine residues in municipal wastewater were reported by 15 cities, with the highest mass loads being detected in cities in Denmark, Spain, Italy and Portugal (see the figure Ketamine residues in wastewater in selected European cities, 2022, below)."