cannabis use in bipolar disorder (BD), with frequent cannabis use being associated with heightened risk of BD onset [154] and/or exacerbation of BD symptomology [154,155,156]. It is worth noting that these effects of long-time use of cannabis are in opposition to the effects of acute cannabis use, which seems to lead to an improvement in BD symptoms [157]. As for MDD, there are studies that found no statistically significant correlation between cannabis use and BD consequences when other factors were considered [157,158]. Anxiety symptoms seem to be higher in cannabis users compared with non-users [159] and are enhanced with the earlier onset of cannabis use [159,160,161,162]. Another condition, which can be related to anxiety and depression, is post-traumatic stress disorder (PTSD), for which cannabis is being used either as self-medication or doctor-prescribed medication. While those undergoing acute or short time treatment, mostly medically assisted, seem to show some benefits in lowering anxiety levels and ameliorating the quality of life, it has been shown that daily cannabis use is positively associated with increased severity of PTSD symptoms [163]. Most of the evidence supports an association of long-time cannabis use with a higher risk of PTSD symptoms and heightened negative affect [128,163,164].
