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Cannabis use has been associated with psychosis through exposure to delta-9-tetrahydrocannabinol (Δ9-THC), its key psychoactive ingredient. Although preclinical and human evidence suggests that Δ9-THC acutely modulates glial function and hypothalamic-pituitary-adrenal (HPA) axis activity, whether differential sensitivity to the acute psychotomimetic effects of Δ9-THC is associated with differential effects of Δ9-THC on glial function and HPA-axis response has never been tested.
A double-blind, randomized, placebo-controlled, crossover study investigated whether sensitivity to the psychotomimetic effects of Δ9-THC moderates the acute effects of a single Δ9-THC dose (1.19 mg/2 ml) on myo-inositol levels, a surrogate marker of glia, in the Anterior Cingulate Cortex (ACC), and circadian cortisol levels, the key neuroendocrine marker of the HPA-axis, in a set of 16 healthy participants (seven males) with modest previous cannabis exposure.
The Δ9-THC-induced change in ACC myo-inositol levels differed significantly between those sensitive to (Δ9-THC minus placebo; M = −0.251, s.d. = 1.242) and those not sensitive (M = 1.615, s.d. = 1.753) to the psychotomimetic effects of the drug (t(14) = 2.459, p = 0.028). Further, the Δ9-THC-induced change in cortisol levels over the study period (baseline minus 2.5 h post-drug injection) differed significantly between those sensitive to (Δ9-THC minus placebo; M = −275.4, s.d. = 207.519) and those not sensitive (M = 74.2, s.d. = 209.281) to the psychotomimetic effects of the drug (t(13) = 3.068, p = 0.009). Specifically, Δ9-THC exposure lowered ACC myo-inositol levels and disrupted the physiological diurnal cortisol decrease only in those subjects developing transient psychosis-like symptoms.
The interindividual differences in transient psychosis-like effects of Δ9-THC are the result of its differential impact on glial function and stress response.
Brain imaging studies have shown altered amygdala activity during emotion processing in children and adolescents with oppositional defiant disorder (ODD) and conduct disorder (CD) compared to typically developing children and adolescents (TD). Here we aimed to assess whether aggression-related subtypes (reactive and proactive aggression) and callous-unemotional (CU) traits predicted variation in amygdala activity and skin conductance (SC) response during emotion processing.
We included 177 participants (n = 108 cases with disruptive behaviour and/or ODD/CD and n = 69 TD), aged 8–18 years, across nine sites in Europe, as part of the EU Aggressotype and MATRICS projects. All participants performed an emotional face-matching functional magnetic resonance imaging task.
Differences between cases and TD in affective processing, as well as specificity of activation patterns for aggression subtypes and CU traits, were assessed. Simultaneous SC recordings were acquired in a subsample (n = 63). Cases compared to TDs showed higher amygdala activity in response to negative faces (fearful and angry) v. shapes. Subtyping cases according to aggression-related subtypes did not significantly influence on amygdala activity; while stratification based on CU traits was more sensitive and revealed decreased amygdala activity in the high CU group. SC responses were significantly lower in cases and negatively correlated with CU traits, reactive and proactive aggression.
Our results showed differences in amygdala activity and SC responses to emotional faces between cases with ODD/CD and TD, while CU traits moderate both central (amygdala) and peripheral (SC) responses. Our insights regarding subtypes and trait-specific aggression could be used for improved diagnostics and personalized treatment.
Cortical glutamatergic dysfunction is thought to be fundamental for psychosis development, and may lead to structural degeneration through excitotoxicity. Glutamate levels have been related to gray matter volume (GMV) alterations in people at ultra-high risk of psychosis, and we previously reported GMV changes in individuals with high schizotypy (HS), which refers to the expression of schizophrenia-like characteristics in healthy people. This study sought to examine whether GMV changes in HS subjects are related to glutamate levels.
We selected 22 healthy subjects with HS and 23 healthy subjects with low schizotypy (LS) based on their rating on a self-report questionnaire for psychotic-like experiences. Glutamate levels were measured in the bilateral anterior cingulate cortex (ACC) using proton magnetic resonance spectroscopy, and GMV was assessed using voxel-based morphometry.
Subjects with HS showed GMV decreases in the rolandic operculum/superior temporal gyrus (pFWE = 0.045). Significant increases in GMV were also detected in HS, in the precuneus (pFWE = 0.043), thereby replicating our previous finding in a separate cohort, as well as in the ACC (pFWE = 0.041). While the HS and LS groups did not differ in ACC glutamate levels, in HS subjects ACC glutamate was negatively correlated with ACC GMV (pFWE = 0.026). Such association was absent in LS.
Our study shows that GMV findings in schizotypy are related to glutamate levels, supporting the hypothesis that glutamatergic function may lead to structural changes associated with the expression of psychotic-like experiences.
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