Inhaling vaporized cannabis containing 10 mg of THC acutely increased blood levels of the endocannabinoid anandamide by 18% and several related noncannabinoid lipids, but adding 10, 20, or 30 mg of CBD did not alter these effects. Over four sessions spaced about two weeks apart, pre-inhalation levels of anandamide and one related compound progressively declined, possibly due to repeated THC exposure or reduced anxiety. The findings suggest that CBD, at the doses tested, does not modulate THC's acute influence on endocannabinoid concentrations, though higher or chronic CBD doses might have an effect.
Abruptly stopping heavy, daily cannabis use can trigger psychosis, both in people experiencing their first episode and in those with a pre-existing psychotic disorder. A systematic review of 21 studies identified 44 individuals whose psychosis began after cannabis withdrawal, and a health-record search found another 68 cases. Almost all were daily users who stopped abruptly. Those who resumed cannabis after the acute psychotic episode were far more likely to relapse than those who abstained (odds ratio 13.9). The findings indicate that acute psychotic symptoms can emerge after cannabis cessation, not only during its use.