Caffeine-induced psychosis

Caffeine acts as an antagonist of adenosine receptors, particularly A1 and A2A receptors. Under normal conditions, adenosine inhibits neurotransmission, which promotes sleep and suppresses arousal. By blocking these receptors, caffeine limits adenosine's inhibitory influence, which results in increased neuronal activity and the enhanced release of excitatory neurotransmitters, such as dopamine and glutamate.

This mechanism contributes to improved alertness, attention, and mood at moderate doses. However, high doses or chronic overuse may overstimulate dopamine pathways in the brain, particularly in areas like the mesolimbic system, which are associated with the development of psychotic symptoms.^[13]

The elevated dopaminergic activity resembles the neurochemical abnormalities observed in psychotic disorders to a lesser degree, and may trigger hallucinations, delusions, or manic symptoms, particularly in individuals who are genetically or biologically vulnerable.^[9]

Additionally, caffeine-induced sleep deprivation, anxiety, and increased arousal can further exacerbate the risk of psychotic symptoms, either independently or in combination with other stressors or substances.^[14]

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Though a definitive causal relationship has not been established, caffeine's effect on dopamine levels may increase arousal and contribute to the onset of psychotic symptoms. Additionally, symptom improvement has been observed following caffeine reduction in individuals with pre-existing psychotic disorders. These findings suggest that individuals with a predisposition to psychosis may possess a lower threshold for developing psychopathological symptoms in response to caffeine intake.^[7]

People with schizophrenia may be more inclined to overuse caffeine for a variety of reasons. Many people with schizophrenia use caffeine to combat boredom or to fight the sedating effects of antipsychotic medications. Many antipsychotics can also cause dry mouth. Additionally, people with schizophrenia may experience psychogenic polydipsia (excessive thirst). These factors could increase the amount of caffeine one may consume.^[15]

80% of people with schizophrenia are smokers. Smoking tends to deplete much of the ingested caffeine, so users with schizophrenia may consume more caffeine than others to make up for this.^[15]

"Caffeine use can cause restlessness, nervousness, insomnia, rambling speech, and agitation",^[15] worsening the symptoms of schizophrenia. "Caffeine is metabolized by the CYP1A2 enzyme and also acts as a competitive inhibitor of this enzyme. Thus, caffeine can interact with a wide range of psychiatric medications, including antidepressant agents, antipsychotic agents, antimanic agents, antianxiety agents, and sedative agents."^[16]

Consuming less than 250 mg of caffeine a day has been associated with better results on cognitive tasks in people with schizophrenia. However, more research still needs to be done to determine if the amount of caffeine that is safe to consume by people with schizophrenia (>250 mg/a day) is the same as that for the general population of people without schizophrenia.^[17]