The early identification of psychosis: can lessons be learnt from cardiac stress testing?

Assessing the Relationship between Sense of Agency, the Bodily-Self and Stress: Four Virtual-Reality Experiments in Healthy Individuals

The bodily-self, our experience of being a body, arises from the interaction of several processes. For example, embodied Sense of Agency (SoA), the feeling of controlling our body’s actions, is a fundamental facet of the bodily-self. SoA is disturbed in psychosis, with stress promoting its inception. However, there is little knowledge regarding the relationship between SoA, stress, and other facets of the bodily-self. In four experiments manipulating embodied SoA using a virtual hand (VH), we examined (1) How is embodied SoA related to other facets of the bodily-self?; and (2) How is SoA impacted by stress? We found that increased alteration of the VH significantly decreased subjective ratings of SoA and body ownership (Exp. 1), supporting the close relation between SoA and body ownership. Interoceptive accuracy and SoA were positively correlated (Exp. 3), connecting awareness to one’s actions and cardiac signals. Contrary to our expectations, SoA was not related to trait anxiety (Exp. 3), nor did induced stress impair SoA (Exp. 4). Finally, we found a negative correlation between self-reported prodromal symptoms and SoA. These results strongly support the connection between SoA and the bodily-self. Whereas, SoA was not impaired by stress, and weakly related to psychotic symptoms.

Basic self-disturbance, neurocognition and metacognition: A pilot study among help-seeking adolescents with and without attenuated psychosis syndrome

AIM

The goal of this pilot study was to assess the association between basic self-disturbance (SD) and deficits in neurocognitive and metacognitive functioning among help-seeking adolescents with and without attenuated psychosis syndrome (APS).

METHODS

Sixty-one non-psychotic, help-seeking adolescents (age 13-18) were assessed with the examination of anomalous self-experience, the structured interview for prodromal syndromes and a new metacognitive approach to neurocognitive assessment applied to two non-social (executive functions and verbal memory) and two social (theory of mind and emotion recognition) domains. After each answer, subjects were also requested to indicate their level of confidence in the answer and to decide whether they desired it to be "counted" toward their total score on the task. Each volunteered answer earned a 5-cent gain if correct, but an equal fine if wrong.

RESULTS

As hypothesized, metacognitive monitoring and control had a significant contribution to the prediction of SD over and above neurocognitive functioning and attenuated psychotic symptoms. However, the direction of this association was positive rather than negative. Also, inconsistent with or hypothesis, it was not moderated by the presence of APS.

CONCLUSIONS

These pilot results provide preliminary support a modest association between SD and metacognition, which is not reducible to neurocognition and APS. In addition, they raise an intriguing possibility regarding metacognitive monitoring and control being indicators of hyper-reflectivity that characterizes individuals with SD. However, further research with larger samples and high-stress assessment conditions are needed to assess this possibility.

Human Laboratory Studies on Cannabinoids and Psychosis

Some of the most compelling evidence supporting an association between cannabinoid agonists and psychosis comes from controlled laboratory studies in humans. Randomized, double-blind, placebo-controlled, crossover laboratory studies demonstrate that cannabinoid agonists, including phytocannabinoids and synthetic cannabinoids, produce a wide range of positive, negative, and cognitive symptoms and psychophysiologic deficits in healthy human subjects that resemble the phenomenology of schizophrenia. These effects are time locked to drug administration, are dose related, and are transient and rarely necessitate intervention. The magnitude of effects is similar to the effects of ketamine but qualitatively distinct from other psychotomimetic drugs, including ketamine, amphetamine, and salvinorin A. Cannabinoid agonists have also been shown to transiently exacerbate symptoms in individuals with schizophrenia in laboratory studies. Patients with schizophrenia are more vulnerable than healthy control subjects to the acute behavioral and cognitive effects of cannabinoid agonists and experience transient exacerbation of symptoms despite treatment with antipsychotic medications. Furthermore, laboratory studies have failed to demonstrate any "beneficial" effects of cannabinoid agonists in individuals with schizophrenia-challenging the cannabis self-medication hypothesis. Emerging evidence suggests that polymorphisms of several genes related to dopamine metabolism (e.g., COMT, DAT1, and AKT1) may moderate the effects of cannabinoid agonists in laboratory studies. Cannabinoid agonists induce dopamine release, although the magnitude of release does not appear to be commensurate to the magnitude and spectrum of their acute psychotomimetic effects. Interactions between the endocannabinoid, gamma-aminobutyric acid, and glutamate systems and their individual and interactive effects on neural oscillations provide a plausible mechanism underlying the psychotomimetic effects of cannabinoids.