Welcome to the EPA 2022 Interactive Programme 

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This presenation summarizes the effects of adolescent cannabis use on brain functioning and cognitive correlates using structural and functional neuroimaging tools and standardised neuropsychological tests. Based on longitudinal epidemiological studies, it also reflects possible effects of adolescent and young adult cannabis use on cognitive performance in adult life and the completion of secondary education. The are two important messages to adolescents and young adults: First, cannabis has potentially detrimental effects on cognition, brain and educational outcomes that persist beyond acute intoxication. Second, impaired cognitive function in cannabis users appears to improve with sustained abstinence.

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Even if most people use cannabis without many negative consequences, some experience cannabis related harms. At higher levels of intake, one of these harms could be psychotic symptoms and even cannabis-induced psychosis. During the last years, we have seen increased treatment seeking for cannabis use disorders in Europe. Parallel with this increase we have seen an increase in the incidence of cannabis induced psychosis in all Scandinavian countries and an increased population attributable fraction for cannabis on the prevalence of schizophrenia has been demonstrated. All this may reflect increased use of cannabis, but more likely increased content of D9-tetrahydrocannabinol (THC) is most cannabis products. Many have also pointed to the fact that we have seen an increase in the incidence of schizophrenia in the same period, maybe attributable to cannabis use. If we also take into consideration that up to one third of those with cannabis-induced psychosis over time receive a diagnosis of schizophrenia, we may see at least two implications. Firstly, these findings strengthens the evidence for a causative relationship between cannabis use and schizophrenia, a causative relationship that man have suggested for several years, but that has had some opponents. Secondly, it points to cannabis-induced psychosis should be considered to be a part of the ICD-10 F2-chapter rather than the F1-chapter. This may be true also for the other substance-induced psychosis (F1x.5). An additional argument for this is that for no other psychotic diagnosis, a precipitation factor is mentioned in the diagnosis.

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Regular cannabis use is associated with several adverse health outcomes including psychosis and cannabis use disorders[ . In the last decade, prevalence of last-month cannabis use increased by 27% and rate of treatment demand rose from 27 to 35.1 per 100000 inhabitants in Europe. Cannabis legal status is changing worldwide, and recently two European countries (Malta and Luxembourg) legalized its production, sales and use. Even United Nations withdrew cannabis from Schedule IV of the Single Convention on Narcotic Drugs (retained in Schedule I). This new scenario aligns cannabis more closely with alcohol, prescribed drugs or tobacco than illegal drugs. Implementing prevention and harm reduction strategies will be even more relevant in the nearly future. Based on the history with alcohol or tobacco, frequency of use alone misestimates the risks due to limited capture of variations of quantity per day of use on regular users. Standardisation of cannabis use has been proposed in the literature as an instrument to assessing the level of risk. In the Lisbon Addictions Conference (2019) a group of 32 professionals from 13 countries and 10 disciplines participated in a back-casting foresight exercise aiming to addresses challenges of implementation of SJU. They proposed three key steps in the implementation of SJU: 1) constitution of task-force for an evidence-based approach to SJU; 2) expanding the available data on cannabis-related risks; 3) examining the relationship between ‘risky use’ and SJU.