An Investigation into Caffeine Intake, Cognition, and Symptomatology in Schizophrenia Patients
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Patients with schizophrenia consume significantly more caffeine than the general population. Despite this, few studies report on caffeine use, and even fewer on the association between caffeine intake and how it might affect cognition. In healthy (non-psychiatric) controls, caffeine use has been associated with better cognitive performance on many of the cognitive domains typically impaired in schizophrenia patients. This cross-sectional study assessed moderate versus high caffeine users on measures of cognitive functioning and symptomatology in 19 participants diagnosed with schizophrenia or schizoaffective disorder. Primary analysis compared moderate versus high caffeine users on measures of working memory, attention/vigilance, processing speed, verbal learning, and visual learning. Secondary analysis compared moderate versus high caffeine users on positive symptoms, negative symptoms, and cognitive symptoms (i.e., cognitive deficits). This study also used open-ended survey questions to better understand the role of caffeine for schizophrenia patients, and themes from their responses were reported. Measures included the Cogstate battery and the Positive and Negative Syndrome Scale (PANSS). Participants were placed into one of two caffeine groups based on self-reported daily caffeine intake: moderate dose (0-250 mg/day) or high dose (251 mg or more/day). T-tests for independent samples were carried out to assess for differences between the two groups on demographic and illness-related variables and on measures of cognitive functioning and symptomatology. Results found that, with respect to demographic and illness- related variables, high caffeine users were prescribed higher antipsychotic doses and were more dependent on nicotine than moderate caffeine users. For cognitive measures, executive function was significantly different between groups such that moderate caffeine users demonstrated a better performance than high caffeine users on the Groton Maze Learning Test. There was a trending difference for a measure of verbal learning and memory, such that moderate caffeine users performed better than high caffeine users on the International Shopping List Test. Assessments of symptoms discovered a significant group difference for the negative factor, such that high caffeine users demonstrated fewer negative symptoms than moderate caffeine users. These results appear to suggest that moderate, rather than high, caffeine consumption is associated with better cognitive functioning, but that high caffeine consumption, rather than moderate, is associated with fewer negative symptoms in schizophrenia outpatients, without necessarily exacerbating positive symptoms. However, given the few studies that are available, additional research is warranted.