The endogenous cannabinoid system is a signaling system of the human body that comprises endocannabinoids (such as anandamide and 2-AG), cell-surface receptors (CB1 and CB2), as well as proteins responsible for the synthesis, degradation and transport of endocannabinoids. This system is widely expressed in the brain, and has been shown to control processes involving learning and memory, attention, pain perception, and emotions while its malfunction has been linked with mental disorders including Parkinson’s disease. Currently, an accumulating body of research has revealed that the sleep-wake cycle is also under the influence of the endocannabinoid system. For instance, in lab mice, injection of anandamide induces sleep, so does the pharmacological inhibition of the protein that degrades it. In contrast, blocking the CB1 cannabinoid receptor (which is activated by anandamide as well as THC, the psychoactive component of cannabis) promotes wakefulness.
Dreaming is a mental activity occurring during sleep, characterized by emotions and sensory perceptions, and involved in memory consolidation. Because of the significant overlap between defining components of dreaming and functions of the endocannabinoid system, scientists have begun to hypothesize that this system might modulate dream activity. Some scientific experiments using animal models have emerged to elucidate the mechanisms of this relationship. Moreover, preliminary studies in humans have indicated that treatment with cannabinoids decreases post-traumatic stress disorder symptoms, including nightmares. Nonetheless, the role of the endocannabinoid system in dreams generation or control remains under-explored, mostly due to methodological challenges in investigating this subject.