Finally, that cannabinoids might exert a causal influence at a cellular level cannot be ruled out. For instance, a recent study shows that, in rodents, administration of THC was associated with reduced spatial working memory via activation of astroglial cannabinoid 1 receptors, which, in turn, activated glutamate receptors that led to long-term depression in synaptic strength in the hippocampus (107). While there are questions regarding how the levels of THC administered to the rodents compare with typical patterns of human cannabis use, this study (and others) hints at possible causal mechanisms that operate with such a degree of biological intricacy so as to remain entirely undetected in genetic epidemiological experiments.
