Effects of phytocannabinoids, synthetic and semi-synthetic cannabinoids on microglia and astrocytes: Review of neuroinflammatory mechanisms

Abstract Over 120 phytocannabinoids and 190 synthetic and semi-synthetic cannabinoids have been identified. Many of these currently circulate in recreational and illicit drug markets. Epidemiological evidence indicates a progressive increase in their use but long-term effects of cannabinoids on the CNS remain poorly understood. Exogenous cannabinoids can interact with cannabinoid receptor CB2, which is expressed on astrocytes and microglia, the key regulators of neuroinflammatory responses. Dysregulated or chronic microglial activation can sustain neuroinflammation, a central mechanism underlying neurodegenerative diseases. Clarifying cannabinoid-induced alterations in glia is therefore crucial both because their widespread consumption and the global burden of neurodegenerative disorders, for which cannabinoids might offer therapeutic potential. This review was conducted by a multidisciplinary team following JBI and PRISMA-ScR guidelines that systematically mapped available evidence across PubMed, Scopus and Web of Science. The findings are thematically organized and qualitatively summarized and indicate compound and time-dependent effects. Acute exposure appears to be neuroprotective whereas chronic effects remain unclear. Preliminary data suggest that some synthetic and semi-synthetic cannabinoids may retain protective actions while Δ9-tetrahydrocannabinol (THC) may promote glial activation and neuroinflammation, These results underscore the need for further in vivo and longitudinal studies to evaluate long-term impacts and inform safe therapeutic and regulatory strategies.