In healthy populations, caffeine appears to have beneficial effects on health; however, patients with bipolar disorder (BD) are routinely advised to limit caffeine use in psychoeducation programmes. We aimed to examine all literature reporting whether caffeine intake/withdrawal impacts the natural course of BD, in terms of clinical outcomes.
PubMed, Embase and PsycINFO were searched (up to 17/07/2020) and all studies reporting data on individuals with BD comparing a measure of caffeine use with illness severity (symptoms of mania, depression, psychosis, anxiety, sleep or suicidality) were included.
Of the 1678 records reviewed, 17 studies met inclusion criteria (10 case reports, 1 retrospective cohort study, 5 cross-sectional studies, 1 interventional study). Most case reports described people with BD switching to manic, hypomanic or mixed states after consuming caffeine in variable amounts and/or whose serum lithium concentrations increased after reducing caffeine consumption. The interventional study found that caffeine may suppress lithium concentrations, while the retrospective cohort study reported that participants who drank coffee had more suicidality than non-drinkers.
The literature examining clinical effects of caffeine in patients with BD is not conclusive. Acute increases in caffeine consumption may precede the occurrence of manic symptoms in patients with BD, potentially through a direct stimulant effect, affecting sleep pattern and/or the metabolism of lithium or other medications, although increases in caffeine intake could also be a consequence of an ongoing manic relapse or a prodromal sign. Further research is needed to determine whether caffeine use impacts the long-term prognosis of BD.

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