Increased CB^sub 2^ mRNA and anandamide in human blood after cessation of cannabis abuse

In previous studies, long-term cannabis use led to alterations of the endocannabinoid system including an increase in CB^sub 1^ and/or CB^sub 2^ receptor messenger RNA (mRNA) in blood cells and an increase in the serum level of the endocannabinoid 2-arachidonoyl glycerol. However, in those studies, cannabis use was stopped only few days before testing or not interrupted at all. Therefore, one cannot decide whether the alterations are due to long-term cannabis abuse or are confounded by acute effects of cannabis. Blood was sampled from donors that had smoked marijuana >=20 times in their lives but had abstained from cannabis for >=6 months (high-frequency users, HFU) and from controls (cannabis use =20 times in their lives and stopped cannabis use at least 6 months before the study show an increase in CB^sub 2^ receptor mRNA in the blood and in serum anandamide level. These alterations resemble those obtained for marijuana smokers that had stopped cannabis use only few days before testing and may be implicated in the pathogenesis of disorders associated with long-term cannabis use.