Hvilke varige skadevirkninger har lang tids bruk av cannabis på kognitive funksjoner.

Abstract

Background: Cannabis is the world’s most commonly used illicit drug, being used of about 4 % of the total global population between 15 and 64 years of age. After the discovery of the endocannabinoid system there has been an increase in the research about cannabis and THC and its potential use as a therapeutical drug. Hence there has also been renewed interest in its possible negative effects. Aims: To highlight recent knowledge and literature about the possible non-acute irreversible effects of long-term cannabis use on cognitive functions. And if possible draw conclusions on the subject. Method: A systematical search on the databases Pubmed and Cochrane Library with key words; cannabis, cannabinoids, hasjis, marijuana, cognition, cognitive dysfunction, learning, memory, long-term and non-acute. Among other inclusion criteria was a controlled abstinence period from cannabis of at least 25 days for participants. Conclusions: 8 studies that matched all criteria. In two of these the authors concluded there were no evidence for cognitive impairments 28 days or more after end of use. One of them was the only longitudinal study with pre-THC-debut data of participants. A third study found that early-onset users exhibited poorer cognitive performance than late-onset users. This founding was supported by yet another. The only meta-study found only small significant differences on the learning and forgetting domaines. Three studies also measured brain activity in cannabis users and all found alterations compared to non-using controls, but only one also found dose-related differences in test performance.