BACKGROUND: Cannabis use has increased across Europe over the last decade, accompanied by growing availability of high-potency THC products and rising psychiatric presentations. Despite these trends, European countries differ substantially in monitoring systems, clinical preparedness and public health responses. These disparities are especially visible between Western Europe, which has more developed pharmacovigilance systems, diagnostic networks, and addiction psychiatry services, and other regions. Compared with other regions, in Central and Eastern Europe cannabis-related psychiatric complications remain systematically underestimated.

METHODS: We conducted a narrative review of peer-reviewed literature, epidemiological reports and national health data published between 2015 and 2025. Sources included EMCDDA, WHO Europe, national statistical agencies and clinical studies on psychiatric outcomes associated with cannabis use.

FINDINGS: Cannabis is the most commonly used illicit psychoactive substance in Europe, with higher prevalence in Western countries but rapid growth across Central and Eastern Europe. The proliferation of high-potency cannabis (>15-25%) is consistently linked to elevated risks of psychosis, anxiety, panic symptoms, derealisation episodes and cannabis use disorder. Western Europe demonstrates better detection of cannabis-related psychiatric presentations, whereas Central and Eastern Europe show a hidden clinical burden driven by stigma, limited screening, inconsistent diagnostic practices and the absence of structured monitoring systems. Health systems vary widely in preparedness, particularly regarding early identification of high-risk use, addiction psychiatry integration and routine collection of psychiatric outcome data.

INTERPRETATION: Cannabis use is linked to a growing mental health burden in Europe. Stronger THC products and uneven health systems make this problem worse. In Central and Eastern Europe, many cannabis-related mental health problems are missed or not reported. Better monitoring, clearer diagnostic rules, and coordinated action across Europe are needed.