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17-03-2011 | Mental health | Article

Cannabis use linked to brain matter deficits in young schizophrenics


Free abstract

MedWire News: Cannabis use is associated with grey and white matter deficits in patients with adolescent-onset schizophrenia, research shows.

"Numerous epidemiological surveys have shown a link between cannabis use and the risk of schizophrenia… [and] there appears to be a dose-dependent relationship, with a higher risk of schizophrenia predicted by the earlier age of cannabis use," explain Anthony James (Warneford Hospital, Oxford, UK) and team.

However, they add that it is not known whether cannabis use affects neurodevelopment in adolescents with schizophrenia.

To investigate, the team studied 16 adolescents with schizophrenia who had a history of cannabis use, 16 adolescent schizophrenia patients without such a history, and 28 mentally healthy controls without such a history who were matched to age, gender, and handedness.

All of the participants underwent magnetic resonance imaging of the brain.

Compared with controls, all of the schizophrenia patients showed grey matter deficits in the prefrontal cortex, superior and inferior temporal gyrus, temporal pole, fusiform gyrus, lateral occipital cortex, inferior, middle, and superior frontal gyrus as well as the supplementary motor cortex.

Schizophrenia patients also had reduced fractional anisotropy (FA) - an indicator of white matter deficits - in several brain areas compared with controls.

Among the schizophrenia patients, those with a history of cannabis use had grey matter deficits in the temporal fusiform gyrus, parahippocampal gyrus, ventral striatum, right middle temporal gyrus, insular cortex, precuneus, right paracingulate gyrus, dorsolateral prefrontal cortex, left postcentral gyrus, lateral occipital cortex, and cerebellum compared with those who did not.

Schizophrenia patients with a history of cannabis use also showed reduced FA in the brain stem, internal capsule, corona radiata, and the superior and inferior longitudinal fasciculus compared with those without such a history.

However, there were no significant differences in cognition between the two schizophrenia groups, and both had similar levels of positive and negative symptoms, the researchers note.

Both groups of schizophrenia patients had poorer cognition than controls.

James and team conclude in the journal Schizophrenia Research: "Our study showed that early cannabis abuse is associated with greater white matter and grey matter changes than in adolescent-onset schizophrenia subjects generally.

"We suggest that this is due to the critical period of development of adolescent brain."

They add: "Further work on the effects of cannabis on targeted pathways around the critical period of puberty is warranted, particularly in view of its putative role in schizophrenia and its widespread use."

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Mark Cowen

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