Understanding caffeine's impact on sustained attention in early phase psychosis: Unveiling cognitive insights through...

Cognitive impairment, particularly in attention and working memory, is a notable feature of schizophrenia (SZ). Individuals with SZ frequently consume high levels of caffeine, often exceeding 550 mg daily, yet the cognitive effects of this excessive intake - especially in the early stages of the illness - remain unexplored. This study is the first to investigate the acute effects of caffeine on cognition in SZ using a rigorous double-blind, placebo-controlled design. Utilizing electroencephalography (EEG)-derived event-related potentials (ERPs) and the AX-continuous performance task (AX-CPT), we examined behavioural and neurophysiological markers of sustained attention, including P300 amplitude and latency. Our sample included individuals within the first five years of their SZ diagnosis (n = 11) and healthy controls (n = 14) aged 20 - 38 (HC: M = 22.5, SZ: M = 28.2). Findings revealed that within the caffeine condition, individuals with SZ exhibited enhanced P300 amplitudes and shorter latencies for the priming stimulus compared to controls. Behavioural performance, however, did not support this and found individuals with SZ performed worse than controls, suggesting the enhancement of cognitive resources during the caffeine condition does not significantly improve performance in individuals with SZ. Correlational findings suggest a potential interaction between symptomology and caffeine's cognitive effects, whereby increased positive symptoms were associated with increased amplitudes, while, negative symptoms were associated with latency findings. These findings challenge the assumptions that caffeine consumption enhances cognitive function in SZ, at least at the doses tested. Future research should explore caffeine's effects at intake levels that are more representative of each individual's habitual consumption to better determine whether chronic high doses exert differential effects on cognition in this population.