Psychosis is a state of mind in which a person loses touch with reality through hallucinations, paranoia, or delusions. In a world where people joke about being addicted to caffeine, and many drink large cups of strong coffee at home, at work, and in cafés, you should be aware that caffeine can induce some types of mental illness.
Psychosis in healthy people
Clinical case studies suggest that caffeine can induce psychosis in otherwise healthy people. One study described a patient who started suffering from paranoia and delusions after consuming a large amount of caffeine . The patient’s psychotic symptoms subsided naturally after reducing caffeine consumption for 7 weeks without taking any anti-psychotic medicine. Another clinical case study reported a patient who had been drinking several cups of coffee and energy drinks each day . The patient sought help because of hallucinations that involved seeing things that were not there and having paranoia about being followed . The patient was also experiencing delusions of reference (a type of delusion involving thinking that trivial or innocuous things have great personal significance or meaning) by being preoccupied with the number 33 . Further longitudinal research is needed to explore whether people who consume a high amount of caffeine are at greater risk of psychosis.
Worsening symptoms for people with psychotic disorders
Caffeine can also make people who are already suffering from a psychotic disorder suffer a worsening of symptoms. A clinical case study reported a patient who had been in remission from paranoid schizophrenia for several years with regular antipsychotic medication but no hospitalisation or caffeine consumption in that period . The patient then started drinking up to 10 cans of energy drinks every day for about 8 weeks and this was followed by psychotic symptoms such as paranoia and delusions. After the patient was hospitalised and not allowed any caffeine for 10 days, the psychotic symptoms lessened, and the patient was discharged. The patient had been consuming 20mg of caffeine per kilogramme of body weight per day, which the authors noted is far below the commonly reported toxicity level of caffeine .
Caffeine and brain receptors
Caffeine is clinically classed as a drug because it has significant effects on the brain and body. The psychoactive effects of caffeine are similar to some of the effects of stimulant drugs such as amphetamines or cocaine . Caffeine is highly addictive because it activates reward-orientated mechanisms within the brain, giving people unpleasant withdrawal symptoms such as headaches or brain “fog” when they stop or reduce it. Drinking coffee and other caffeinated products has significant effects on the brain and body because caffeine interacts with the dopamine system. Caffeine antagonises the brain’s A1 and A2 adenosine receptors , explaining its effects on the body’s motor activity, such as boosting exercising activity or increasing physical agitation. Caffeine also disrupts sleep by antagonising the brain’s A1 receptor , which has an important role in helping people sleep, and this can explain why caffeine makes people feel more alert while increasing their risk of insomnia.
Caffeine-related mental disorders
The psychoactive effects of caffeine, as a drug, led the American Psychiatric Association to recognise that caffeine-related disorders exist, with the Diagnostic and Statistical Manual of Mental Disorders (DSM-5, 2013)  listing several caffeine-related disorders. For example, caffeine intoxication disorder is defined by DSM-5 as following consumption of more than 250mg of caffeine, clinically significant disturbance in functioning or distress, and 5 of the following symptoms not caused by another medical condition:
- Diuresis (e.g. frequent urination)
- A flushed face
- Gastrointestinal disturbance (e.g. diarrhoea)
- Muscle twitching
- Periods of being inexhaustible
- Psychomotor agitation (e.g. fidgeting)
- Rambling thoughts or speech
- Tachycardia or arrhythmia (unusually fast or irregular heart beats)
The DSM-5 now also recognises caffeine withdrawal disorder, with symptoms including headaches and finding it difficult to concentrate or feeling depressed . Future versions of the DSM should review research about caffeine-induced psychosis, and consider whether it should be added to the list of caffeine-related mental disorders.
Is caffeine harming your mental health?
If you follow the trend of drinking strong coffee, energy drinks, and other caffeinated products every day, ask yourself whether it could be harming your mental health:
- Is your caffeine consumption toxic: Are you drinking too much caffeine for your body weight every day?
- How much caffeine, for you, is too much? Depending on your physiology (e.g. tolerance, weight) this might be far less than 250mg a day.
- Do you notice symptoms of caffeine intoxication, addiction, or withdrawal that disturb your psychological or physical functioning?
- Have you had psychotic symptoms after consuming caffeine?
If you think that caffeine is harming your mental health, stop or reduce it and speak to your clinician.
 Hedges, D.W., Woon, F.L & Hoopes, S.P. Caffeine-induced psychosis. CNS Spectr, 14(3):127-9. https://doi.org/10.1017/s1092852900020101
 Whiting, W. (2011) New-onset psychosis: Check caffeine use. Current Psychiatry, 10(11), 69. https://www.mdedge.com/psychiatry/article/64520/schizophrenia-other-psychotic-disorders/new-onset-psychosis-check-caffeine
 Cerimele, Joseph & Stern, Adam & Jutras-Aswad, Didier. (2010). Psychosis following excessive ingestion of energy drinks in a patient with schizophrenia. American Journal of Psychiatry, 167(3), 353. https://doi.org/10.1176/appi.ajp.2009.09101456
 Ferré, S. (2007). An update on the mechanisms of the psychostimulant effects of caffeine. Journal of Neurochemistry, 105(4), 1067-1079. https://doi.org/10.1111/j.1471-4159.2007.05196.x
 American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5). Arlington, VA: American Psychiatric Association.