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Cannabis-Induced Psychosis: A Review: Page 2 of 5

Cannabis-Induced Psychosis: A Review: Page 2 of 5

© Elisa Manzati/shutterstock.com© Elisa Manzati/shutterstock.com
A comparison of clinical features of idiopathic vs cannabis-induced psychosisTABLE. A comparison of the clinical features of idiopathic versus cann...
Treatment of cannabis-induced psychosisFigure. Treatment of cannabis-induced psychosis

 

Neurobiology of CIP

Cannabis is considered an environmental risk factor that increases the odds of psychotic episodes, and longer exposure is associated with greater risk of psychosis in a dose-dependent fashion. The drug acts as a stressor that leads to the emergence and persistence of psychosis. While a number of factors play a role in the mechanism by which consumption produces psychosis, the primary psychoactive ingredient is considered to be delta 9-tetrahydrocannabinol (delta9-THC). Properties of delta9-THC include a long half-life (up to 30 days to eliminate the long-acting THC metabolite carboxy-THC from urine) and high lipophilicity, which may contribute to CIP.

During acute consumption, cannabis causes an increase in the synthesis and release of dopamine as well as increased reuptake inhibition, similar to the process that occurs during stimulant use. Consequently, patients with CIP are found to have elevated peripheral dopamine metabolite products.

Findings from a study that examined presynaptic dopaminergic function in patients who have experienced CIP indicate that dopamine synthesis in the striatum has an inverse relationship with cannabis use. Long-term users had reduced dopamine synthesis, although no association was seen between dopaminergic function and CIP.6 This observation may provide insight into a future treatment hypothesis for CIP because it implies a different mechanism of psychosis compared with schizophrenia. As cannabis may not induce the same dopaminergic alterations seen in schizophrenia, CIP may require alternative approaches—most notably addressing associated cannabis use disorder.

Polymorphisms at several genes linked to dopamine metabolism may moderate the effects of CIP. The catechol-o-methyltransferase (COMT Val 158Met) genotype has been linked to increased hallucinations in cannabis users.7 Homozygous and heterozygous genetic compositions (Met/Met, Val/Met, Val/Val) for COMT Val 158Met have been studied in patients with CIP and suggest that the presence of Val/Val and Val/Met genotypes produces a substantial increase in psychosis in relation to cannabis use. This suggests that carriers of the Val allele are most vulnerable to CIP attacks.

There has been much controversy surrounding the validity of a CIP diagnosis and whether it is a distinct clinical entity or an early manifestation of schizophrenia. In patients being treated for schizophrenia, those with a history of CIP had an earlier onset of schizophrenia than patients who never used cannabis.8 Evidence suggests an association between patients who have received treatment for CIP and later development of schizophrenia spectrum disorder. However, it has been difficult to distinguish whether CIP is an early manifestation of schizophrenia or a catalyst. Nonetheless, there is a clear association between the 2 disorders.

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