Association of cannabis with glutamatergic levels in patients with early psychosis: Evidence for altered volume striatal glutamate relationships in patients with a history of cannabis use in early psychosis
Psychosis is a debilitating but quite common mental condition characterized by a disconnection from reality; therefore, multiple ongoing research efforts are dedicated to understanding the mechanism of this disorder. Glutamate is the most abundant excitatory neurotransmitter – chemicals that nerve cells use to send signals to other cells – in the brain and one of its main sites of action is a brain structure known as striatum. Medical research has previously established that psychotic symptoms are related to abnormal glutamate transmission at the striatum.
THC, the main psychoactive compound in cannabis, creates the sense of relaxation and euphoria through binding to and activating the cannabinoid receptor type 1 (CB1), which is very abundant in the brain, especially in the grey matter (neuronal cell body). Because there are widespread neural projections from grey matter regions with high CB1 expression to the striatum, it has been postulated that abnormal glutamate level and distribution pattern may underlie multiple symptoms experienced by patients with a dual diagnosis of psychosis and cannabis use.
Recently, through a large clinical study with four groups: early psychosis patients with and without a history of cannabis use and healthy individuals with and without a history of cannabis use, researchers have found evidence of a significant, unique correlation in early psychosis patients who used cannabis: the more grey matter volume, the higher striatal glutamate level. The causal relationship behind this correlation – whether a history of cannabis use leads to a change in connectivity of these brain regions or the native patterns of some patients’ brains predispose them to heavy cannabis use – remains to be further investigated.