Schizophrenia - cannabis effects

Various studies have been done on the effects of cannabis on the brain. Many give conflicting results (1). Some show an increased risk of schizophrenia-like symptoms (2) and brain re-structuring (3), whereas others find no evidence for a causal link with schizophrenia (4). Brain damage appears to be greater when cannabis is taken in adolescence (5) . Cannabis intake can have similar effects on the brain to schizophrenia. For example, animal studies have shown that cannabis use results in dopamine increase in the mesolimbic area of the brain as its release is associated with pleasure (6) . Chronic cannabis use may result in atrophy of several areas in the brain including grey matter see Fig 8 and schizophrenia-like symptoms which increase with increased use (3) . There appears to be a dose-response relationship where increased use of cannabis results in an increased risk of developing psychosis (7) .

A recent study (8) investigating the effects of cannabis and high-potency cannabis use in different sites across Europe and Brazil show that the incidence of first-episode psychosis increases with frequency of use and potency. The study demonstrated that 12%, 30% and 50% of first episode psychosis cold be prevented in Europe, London and Amsterdam if the use of high-potency cannabis was prevented (8) and that cannabis use may contribute significantly to psychosis incidence (8).

 

Significant grey matter volume reduction could result either from heavy consumption unrelated to the age of onset or instead from recreational cannabis use initiated at an adolescent age. In contrast, the larger grey matter volume detected in the cerebellum of regular smokers without any correlation with the monthly consumption of cannabis may be related to developmental (ontogenic) processes that occur in adolescence i.e. prevents neuronal trimming (3; 9) .

Fig 8 Images show grey matter reduction in regular cannabis users compared with occasional users from: Battistella G, Fornari E, Annoni J-M, et al. Long-Term Effects of Cannabis on Brain Structure. Neuropsychopharmacology 2014;39(9):2041-48. doi: 10.1038/npp.2014.67

 

Legend

Voxel-Based Morphometry results on grey matter. Cold color bar shows regions where gray matter volume is lower in regular smokers compared with occasional ones. Hot color bar represents the opposite contrast. Maps are thresholded at P<0.005 and k>60 and superposed on a standard brain in the MNI space. Figure shows results in planes centered at −26, 7, 14 mm and −48, 10, −19 mm. Color bars represent T score.

 

 

 

References

1. DeLisi LE. The Effect of Cannabis on the Brain: Can it cause brain anomalies that lead to increased risk for Schizophrenia? Current opinion in psychiatry 2008;21(2):140-50. doi: 10.1097/YCO.0b013e3282f51266

2. Szoke A, Galliot AM, Richard JR, et al. Association between cannabis use and schizotypal dimensions--a meta-analysis of cross-sectional studies. Psychiatry Res 2014;219(1):58-66. doi: 10.1016/j.psychres.2014.05.008 [published Online First: 2014/06/01]

3. Battistella G, Fornari E, Annoni J-M, et al. Long-Term Effects of Cannabis on Brain Structure. Neuropsychopharmacology 2014;39(9):2041-48. doi: 10.1038/npp.2014.67

4. Hill M. Perspective: Be clear about the real risks. Nature 2015;525:S14. doi: 10.1038/525S14a

5. Bossong MG, Niesink RJ. Adolescent brain maturation, the endogenous cannabinoid system and the neurobiology of cannabis-induced schizophrenia. Prog Neurobiol 2010;92(3):370-85. doi: 10.1016/j.pneurobio.2010.06.010 [published Online First: 2010/07/14]

6. Oleson EB, Cheer JF. A Brain on Cannabinoids: The Role of Dopamine Release in Reward Seeking. Cold Spring Harbor Perspectives in Medicine 2012;2(8):a012229. doi: 10.1101/cshperspect.a012229

7. Marconi A, Di Forti M, Lewis CM, et al. Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis. Schizophr Bull 2016;42(5):1262-9. doi: 10.1093/schbul/sbw003 [published Online First: 2016/02/18]

8. Di Forti M, Quattrone D, Freeman TP, et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. The Lancet Psychiatry doi: 10.1016/S2215-0366(19)30048-3

9. Lubman DI, Cheetham A, Yucel M. Cannabis and adolescent brain development. Pharmacol Ther 2015;148:1-16. doi: 10.1016/j.pharmthera.2014.11.009 [published Online First: 2014/12/03]