At the European level, the bulk of trend data converge on showing that cannabis use and related problems have increased in the past decade. The available data indicates that rises in prevalence rates were reported in all age groups. Among adults aged 35 to 64 years, prevalence of past month use increased by 50% or more. These findings are similar to reports from European student surveys [46] and recent trends in the USA, where the largest increases in prevalence of use have occurred in middle-aged adults [47]. Consistent with rising prevalence of any use and high-risk use patterns, treatment rates have also risen in many countries, reaching a plateau in 2014. The high level of treatment rates for cannabis creates problems for healthcare providers. Psychosocial interventions such as Motivational Interviewing and Cognitive Behavioural Therapy have been shown to be effective at reducing cannabis use [48,49]. However, there is a lack of approved pharmacotherapies for the treatment of cannabis use disorders, and limited effectiveness of psychosocial interventions for people with comorbid mental health problems such as psychosis [50].
