Hallucinations can be deeply confusing and frightening. They happen when someone sees, hears, smells, feels, or tastes something that isn’t really there.
For people with mental illness, hallucinations are more than just unusual experiences—they are often a sign that something is seriously wrong in the brain.
But what actually causes hallucinations, and why do they happen in some mental health conditions? Scientists have been studying these questions for decades, and while there’s still more to learn, research has uncovered many possible causes.
One of the most well-known conditions linked to hallucinations is schizophrenia. People with schizophrenia often hear voices that aren’t real. These voices might comment on what they’re doing, insult them, or tell them to do things.
Studies using brain scans show that during these hallucinations, parts of the brain linked to hearing and language are highly active—even when no sound is present. This suggests the brain is creating sounds from within, possibly because of chemical imbalances or faulty connections between brain areas.
Another mental health condition that can involve hallucinations is severe depression, especially when it includes psychotic features. In these cases, people may hear critical voices or believe things that are not true.
Anxiety and stress can also trigger hallucinations, especially when someone is under extreme emotional pressure. Post-traumatic stress disorder (PTSD), for example, may involve flashbacks that feel so real they seem like hallucinations.
Dementia, especially Alzheimer’s disease and Lewy body dementia, can also cause hallucinations. These often involve seeing people, animals, or things that aren’t there.
Scientists believe this happens because brain cells are dying in areas involved in vision, memory, and thinking. In fact, visual hallucinations are one of the first signs of Lewy body dementia.
Bipolar disorder can also cause hallucinations, usually during episodes of mania or deep depression. During manic states, people might feel extremely energized and may have delusions or hear voices. During depressive states, they might hear voices that tell them negative things about themselves.
Researchers also know that certain brain chemicals—especially dopamine—play a key role. Dopamine helps transmit messages in the brain and affects how we interpret reality.
When dopamine levels are too high in certain parts of the brain, it can lead to hallucinations. Many antipsychotic medications work by lowering dopamine activity, which often reduces hallucinations.
Sleep problems can also cause hallucinations. People who don’t sleep for long periods—such as during insomnia or severe stress—can start to see or hear things that aren’t real. These hallucinations often go away once the person gets enough rest. Similarly, people with sleep disorders like narcolepsy may have vivid dreams that mix into waking life.
While hallucinations are often linked to mental illness, they can also be caused by medical problems like brain injuries, epilepsy, or even infections that affect the brain. That’s why doctors usually run tests to rule out physical causes when someone first reports hallucinations.
In short, hallucinations are complex and can come from many different sources, especially within mental health conditions. They are not made up or fake—they are real experiences caused by changes in the brain. Understanding what causes them can help doctors find better ways to treat them and help people feel more in control of their minds.
If you care about depression, please read studies about vegetarianism linked to higher risk of depression, and Vitamin D could help reduce depression symptoms.
For more information about health, please see recent studies that ultra-processed foods may make you feel depressed, and these antioxidants could help reduce the risk of dementia.
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