Modulation of the endogenous cannabinoid system as a therapeutic target in the treatment of mental health disorders

Development of effective therapeutic interventions for the treatment of mental health disorders has been a significant driving force in the search to understand the human brain. Current treatments for mental health disorders rely on modulating neurotransmitter systems such as norepinephrine (NE), serotonin (5-HT), dopamine (DA) and γ-aminobutyric acid (GABA) to achieve clinically relevant relief of symptoms. While many medications are available to the clinician that individually target these neural systems, treatment often results in patients reporting unwanted side effects or experiencing incomplete relief. To counter this lack of treatment efficacy, further investigation of other avenues for achieving similar or better outcomes and potentially reach patients refractory to common therapies must be undertaken. One of these potential new target systems is the endogenous cannabinoid system (ECS), which is currently composed of cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). These metabotropic seven transmembrane (7-TM) loop G-protein coupled receptors (GPCR) are responsible for mediating the effects of acute Cannabis ingestion as well as modulating several core functions of the nervous system including emotion, memory, and learning behavior. Due ubiquitous expression of ECS proteins, there is broad overlap between brain regions that show high levels of receptor expression and those thought to be involved in the etiology of a range of mental health disorders including depression, anxiety and schizophrenia. Consequently, modulation of cannabinoid receptor function is a novel and potentially clinically relevant mechanism for influencing the levels of other neuromodulators and neurotransmitters, such as dopamine, that are known to play crucial roles in the progression of mental illness. In addition, characterization of endogenous cannabinoids and cannabinoid receptors with respect to their normal physiological function and possible roles in pathophysiology may provide insight for the development of future ECS-based therapies.