Caffeine is the most commonly used psychoactive substance worldwide, being daily consumed by approximately 80% of the world's population. It may be found not only in the form of beverages and food but also as pharmacologic preparations. Caffeine's consumption is implied in many psychiatric manifestations, from anxiety bursts to psychosis. This symptomatic variation is not only dose-dependent but also affected by various individual factors. Caffeine is a methylxanthine that exerts its primary action in the Central Nervous System (CNS) as an antagonist of the adenosine receptors A1 and A2A, altering the release of neurotransmitters such as dopamine and glutamate. It also interferes with olanzapine and clozapine's hepatic metabolism, increasing its seric levels. Caffeinism is considered when the daily dosage of caffeine consumed is 600–750 mg. Some studies report that dosages above 750 mg/daily may precipitate or exacerbate psychotic symptoms, as well as increase the resistance to neuroleptic treatment. Moreover, it has been demonstrated that patients diagnosed with schizophrenia have significantly larger consumptions of caffeine than other diagnostic groups. Different factors may sustain this, as the relief of side effects due to neuroleptic medication and as a social facilitator.