Mental illness, substance abuse, lack of sleep and certain medications cause people to hallucinate, according to Healthline. High fever may cause hallucinations in the elderly and young children. Other causes of hallucinations include brain trauma, liver failure and toxins.
Schizophrenia, delirium and dementia can cause hallucinations. Alcohol, marijuana, cocaine and steroid abusers may experience hallucinations.
People who do not get enough sleep over a prolonged period of time may have hallucinations. Hallucination may also be associated with vision and hearing problems, notes MedicineNet.
Medications used to treat Parkinson's disease, psychosis, depression and epilepsy may trigger hallucinations, states Healthline. Aripiprazole, haloperidol, clozapine and ziprasidone all have hallucinatory side effects.
People who have a terminal illness, such as acquired immunodeficiency syndrome, kidney failure, liver failure or brain cancer may have hallucinations. Seizures and migraines have also been linked to hallucinations. A person who has an epileptic episode may see flashing lights, shapes or bright spots.
Bereavement, grief and loss may cause a person to have temporary hallucinations, according to Healthline. The individual may hear the person's voice or see his image briefly. However, this type of hallucination goes away as the pain of loss subsides.