Dissociative and metacognitive factors in hallucination-proneness when controlling for comorbid symptoms

Evaluation of state and trait biomarkers in healthy volunteers for the development of novel drug treatments in schizophrenia

Antipsychotic drugs are the mainstay of treatment for schizophrenia but they have little effect on core negative symptoms or cognitive impairment. To meet the deficiencies of current treatments, novel potential compounds are emerging from preclinical research but translation to clinical success has been poor. This article evaluates the possibility that cognitive and physiological abnormalities in schizophrenia can be used as central nervous system biomarkers to predict, in healthy volunteers, the likely efficacy of entirely new pharmacological approaches to treatment. Early detection of efficacy would focus resource on rapidly developing, effective drugs. We review the relevance of selected cognitive and physiological abnormalities as biomarkers in schizophrenia and three of its surrogate populations: (i) healthy volunteers with high trait schizotypy; (ii) unaffected relatives of patients; and (iii) healthy volunteers in a state of cortical glutamate disinhibition induced by low-dose ketamine. Several biomarkers are abnormal in these groups and in some instances there has been exploratory work to determine their sensitivity to drug action. They are generally insensitive to current antipsychotics and therefore their predictive validity cannot be established until novel, therapeutically useful drugs are discovered. Until then such biomarker studies can provide evidence of drugs engaging with the mechanism of interest and encouragement of the concept.

The metacognitive beliefs account of hallucinatory experiences: a literature review and meta-analysis

An influential model of hallucinations proposed by Morrison et al. (1995. Behavioural and Cognitive Psychotherapy, 23(3), 265-280) assumes that dysfunctional metacognitive beliefs lead to the misattribution of intrusive thoughts to external sources, therefore generating hallucinatory experiences. Following a comprehensive review of the literature, a series of meta-analyses was carried out to summarize the empirical findings on the association between hallucination-proneness and different metacognitive beliefs. The results of this research synthesis found little support for the existence of specific associations between hallucinations and dysfunctional metacognitive beliefs. While metacognitive beliefs are robustly associated with hallucination-proneness in non-clinical studies, they were only moderately associated with hallucinations in clinical samples. Additional analyses revealed that, after controlling for the effect of comorbid symptoms, hallucination-proneness was only weakly associated with metacognitive beliefs, suggesting that the large associations observed in previous research might stem from the failure to consider the covariation between different symptoms. These findings have important implications in relation to the role of metacognitive factors in psychopathological symptoms, as well as for the implementation of metacognitive-focused cognitive behavioural techniques for the treatment of psychosis.