Jones Fernyhough 2009 Caffeine, Stress, and Proneness to Psychosis-Like Experiences

2681 Words Oct 16th, 2012 11 Pages
Personality and Individual Differences 46 (2009) 562–564

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Caffeine, stress, and proneness to psychosis-like experiences: A preliminary investigation
Simon R. Jones *, Charles Fernyhough
Department of Psychology, Durham University, South Road, Durham DH1 3LE, UK

a r t i c l e

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a b s t r a c t
In diathesis–stress models of psychosis, cortisol released in response to stressors is proposed to play a role in the development of psychotic experiences. Individual differences in cortisol response to stressors are therefore likely to play a role in proneness to psychotic
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In the only study to systematically administer caffeine (10 mg/kg) directly to patients with schizophrenia, Lucas et al. (1990) found that suspiciousness/paranoia did not change, but that grandiosity and unusual thought content increased (data on hallucinations were not reported). However, such studies may be confounded by the interaction of caffeine with antipsychotic medication (Haslemo, Eikeseth, Tanum, Molden, & Refsum, 2006). One way to avoid this confound is to assume that psychotic experiences exist on a continuum stretching into the healthy population (Johns & van Os, 2001) and examine the relation between caffeine and psychosis-like experiences in the general population. The only study to date to examine the relation between caffeine intake and schizotypy (Larrison, Briand, & Sereno, 1999) found no relation between the two. However, this study used a crude self-report measure of caffeine intake in which participants were simply asked to ‘‘circle the number of caffeinated. . .drinks they consumed

S.R. Jones, C. Fernyhough / Personality and Individual Differences 46 (2009) 562–564


per day or week” (p. 103), and then split individuals into high, moderate and low intake groups, hence reducing the power of the study. Furthermore, it employed a general measure of schizotypy, with no focus on specific experiences such as hallucinations or feelings of persecution. We accordingly set out to

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