The Effects of Caffeine on Anxiety Behavior in Healthy Individuals: A Systematic Review of the Literature

To assess available evidence on the association between anxiety and caffeine consumption in healthy individuals. A high-sensitivity electronic search was performed, as recommended by the Cochrane Handbook, which underwent peer review according to the PRESS Guide, in March 2021 in the following databases: Cochrane Library, MEDLINE via PUBMED, LILACS via VHL, APA PsycNet, EMBASE, Scielo, Scopus, Web Of Science and Cinahl. There were no idiomatic or temporal restrictions regarding the studies obtained. After applying the inclusion and exclusion criteria, the articles were evaluated in a paired manner by two review authors for risk of bias and quality of evidence using the ROB-II tool. Statistical analysis was conducted using R version 1.4.1106 with a fixed-effect model, but the specific statistical tests applied were not detailed. 6999 studies were located, of which 6972 were excluded following the PRISMA protocol, leaving 27 articles at the end. The findings indicate a dose-dependent anxiogenic effect of caffeine. However, variations were observed between individuals with low and high habitual caffeine consumption prior to the intervention. Additionally, evidence suggests that caffeine-induced insomnia may have contributed to increased anxiety in the study population. In general, the findings of the present study were predominantly in favor of caffeine associated with increased anxiety symptoms.