Effect of high-potency cannabis on corpus callosum microstructure.

S Rigucci,A S David,M Di Forti,T R Marques,C M Pariante,F Dell'Acqua,H Taylor,A Simmons,P Girardi,P Dazzan,V Mondelli,S Bonaccorso,R M Murray

doi:10.1017/s0033291715002342

Abstract

The use of cannabis with higher Δ9-tetrahydrocannabinol content has been associated with greater risk, and earlier onset, of psychosis. However, the effect of cannabis potency on brain morphology has never been explored. Here, we investigated whether cannabis potency and pattern of use are associated with changes in corpus callosum (CC) microstructural organization, in patients with first-episode psychosis (FEP) and individuals without psychosis, cannabis users and non-users. The CC of 56 FEP (37 cannabis users) and 43 individuals without psychosis (22 cannabis users) was virtually dissected and segmented using diffusion tensor imaging tractography. The diffusion index of fractional anisotropy, mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity was calculated for each segment. Across the whole sample, users of high-potency cannabis had higher total CC MD and higher total CC AD than both low-potency users and those who never used (p = 0.005 and p = 0.004, respectively). Daily users also had higher total CC MD and higher total CC AD than both occasional users and those who never used (p = 0.001 and p < 0.001, respectively). However, there was no effect of group (patient/individuals without psychosis) or group x potency interaction for either potency or frequency of use. The within-group analysis showed in fact that the effects of potency and frequency were similar in FEP users and in users without psychosis. Frequent use of high-potency cannabis is associated with disturbed callosal microstructural organization in individuals with and without psychosis. Since high-potency preparations are now replacing traditional herbal drugs in many European countries, raising awareness about the risks of high-potency cannabis is crucial.

Highlights

Cannabis use has been associated with an increased risk of subsequent psychosis (Henquet et al 2008; Casadio et al 2011)
We hypothesized that corpus callosum (CC) microstructural organization would be affected in individuals who use higher-potency cannabis, independently of frequency and age of first use. We explored whether this effect would be stronger in those individuals with concomitant psychosis, and investigated which specific segment of the CC, if any, would be altered in relation to cannabis potency
There was no significant difference between patients and individuals without psychosis for years of cannabis use, age at first use, type of cannabis use, frequency of use and potency of cannabis used

Summary

Introduction

Cannabis use has been associated with an increased risk of subsequent psychosis (Henquet et al 2008; Casadio et al 2011). Our group has previously shown that this risk is greater, and onset occurs earlier, in those individuals who use more frequently and those who use cannabis with higher Δ9-tetrahydrocannabinol (THC) content (high-potency types such as ‘skunk’) (Di Forti et al 2009, 2014). While the long-term use of cannabis has been associated with alterations in both brain function and morphology (Lorenzetti et al 2010; Schacht et al 2012; Battistella et al 2014), the effect of potency on the brain has never been explored. The use of cannabis with higher Δ9-tetrahydrocannabinol content has been associated with greater risk, and earlier onset, of psychosis. We investigated whether cannabis potency and pattern of use are associated with changes in corpus callosum (CC) microstructural organization, in patients with first-episode psychosis (FEP) and individuals without psychosis, cannabis users and non-users

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Discussion

Conclusion