Cannabis, psychosis and the thalamus: A theoretical review

• Published in: Neuroscience and biobehavioral reviews Vol. 37; no. 4; pp. 658 - 667
• Main Authors: VUKADINOVIC, Zoran, HERMAN, Merrill S, ROSENZWEIG, Ivana
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 01.05.2013
• Subjects: Animals; Behavioral psychophysiology; Biological and medical sciences; Calcium Channels, T-Type - drug effects; Calcium Channels, T-Type - physiology; Cannabinoids - pharmacology; Cannabis; Cerebral Cortex - physiopathology; Dronabinol - toxicity; Electroencephalography; Fundamental and applied biological sciences. Psychology; Hallucinogens - toxicity; Humans; Neural Pathways - drug effects; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Psychoses, Substance-Induced - physiopathology; Psychoses, Substance-Induced - psychology; Psychotic Disorders - physiopathology; Psychotic Disorders - psychology; Schizophrenia - physiopathology; Schizophrenic Psychology; Thalamus - physiopathology; Source-monitoring deficits; CBD; Theory; T-type calcium channel; Central nervous system; Cannabidaceae; Review; Burst firing; THC; Encephalon; Psychosis; Cannabis; Information source; Δ; Dicotyledones; Angiospermae; Thalamus; Spermatophyta; Higher order thalamic nuclei; T-type calcium channels
• ISSN: 0149-7634; 1873-7528
• DOI: 10.1016/j.neubiorev.2013.02.013

The role of cannabis in the etiology of schizophrenia has been documented as possibly the strongest environmental risk factor. However, the pathomechanism whereby cannabis use increases this risk has not yet been identified. We argue that this pathomechanism may involve direct effects of exogenous cannabinoids on T-type calcium channels in the thalamus. These channels are crucial for amplification of corticothalamic inputs, as well as for the ability of the thalamus to generate neuronal burst firing. Cortically induced thalamic burst firing has been found to be important in trans-thalamic cortico-cortical interactions. Therefore, any potential interference with the burst firing mode in the thalamus could lead to an impairment in these interactions, which in turn causes a relative disconnection between cortical areas. This in turn could result in reduced ability to recognize re-afferent sensory inputs and psychosis. We also argue that the effects of Δ(9)THC are more detrimental compared with the effects of cannabidiol, as the former may increase the excitability of thalamic neurons by its direct effect on T-type calcium channels.