Psychiatry and Clinical Neurosciences
April 18, 2023
Lucy Chester, L. Valmaggia, M. Kempton et al.
Cannabis use is associated with an increased risk of developing psychotic disorders among people already at clinical high risk for psychosis. In a prospective study of this population, cannabis use was linked to a higher incidence of psychotic disorders and to more persistent psychotic symptoms, as well as poorer functional outcomes. The findings strengthen evidence that cannabis acts as a risk factor for psychosis, though the direction of causality remains debated.
Schizophrenia Bulletin Open
January 1, 2020
M. Sami, R. Mccutcheon, U. Ettinger et al.
Both chronic cannabis use and psychotic disorders are linked to abnormalities in how the brain processes visual attention. Using resting-state fMRI, connectivity was measured in the visual and dorsal attention networks of people with early psychosis who did or did not use cannabis, and healthy controls who did or did not use cannabis. Patients with a history of cannabis use showed increased connectivity in the dorsal attention network (134%) and between the visual and dorsal attention networks (285%) compared to non-using controls. In patients who used cannabis, connectivity in these networks correlated with visual hallucinations and with severity of cannabis dependence. The findings suggest that disrupted connectivity in these networks may play different roles depending on cannabis use.
January 1, 2020
D. Oliver, G. Modinos, P. McGuire
No licensed pharmacological treatments exist to prevent the onset of psychosis in people at clinical high risk. This chapter reviews four preclinical models that inform the development of such treatments: neonatal hippocampal lesion, prenatal immune activation, and administration of PCP or methylazoxymethanol acetate (MAM). The neonatal hippocampal model lacks construct validity, evidence linking prenatal immune activation to psychosis is limited, and the chronic PCP model lacks a neurodevelopmental component. The MAM model best reproduces neural and behavioral changes resembling human psychosis onset. Together, these models have advanced understanding of mechanisms underlying psychotic disorders and provide a rationale for novel preventative interventions.
European Neuropsychopharmacology
July 1, 2018
M. Colizzi, P. McGuire, V. Giampietro et al.
Modest previous cannabis use blunts the acute behavioral and neurophysiological effects of ∆9-THC, the main psychoactive ingredient in cannabis. In a double-blind, placebo-controlled challenge, abstinent modest users (average 24.5 lifetime joints) showed worse cognitive performance and stronger right hemispheric brain activation than non-users, regardless of whether they received ∆9-THC or placebo. Acute ∆9-THC caused transient anxiety and psychosis-like symptoms in all participants, with stronger effects in non-users. Non-users under placebo activated specific brain areas for tasks while deactivating others, an opposite pattern to that seen in non-users under ∆9-THC and in cannabis users under placebo. Among non-users, more severe drug-induced symptoms and cognitive impairments correlated with greater neurophysiological changes.