Psychosis is the term used to describe a loss of contact with reality. The person suffering from psychosis has a distorted perception of reality, with thought contents characterised by delusions (of persecution, megalomania, etc.), acoustic-verbal and/or visual hallucinations, that is hearing or seeing things that do not exist. The cause is a brain abnormality, including a chemical disturbance of neuronal communication (especially the neurotransmitters dopamine and serotonin). Psychosis is the expression of a psychological disorder, which can occur in different psychiatric pathologies such as bipolar disorder, depression or schizophrenia, but also in the context substance abuse (e.g. alcohol, cannabis, cocaine, amphetamines, etc.) Schizophrenia is a mental illness characterised by a loss of contact with reality. It affects thoughts, perceptions and behaviour and often has a significant impact on the quality of life of the person suffering from it. A diffuse brain dysfunction is at the basis of the disease and not a split personality as is still often believed. This disease affects several areas of the brain. A small number of people with this disease can become violent, especially those at high risk of suicide. This disease shows the following symptoms: difficulty imagining the actions required to reach one's goal, major concentration problems with forgotten appointments or tasks to accomplish, difficulty following a conversation, difficulty remembering what someone has said or done (here we talk about memory, attention and executive function disorders). To this we can add, in early adulthood, so-called "positive" symptoms such as hallucinations, most often auditory but also olfactory, tactile and visual. Also, delusions ideas of being watched or in danger, that others can read one’s thoughts or that one is controlled by an external force. So-called "negative" symptoms are seen as the person cuts himself off from his friends and activities. The sufferer will de detached from reality, has conversation difficulties, neglects hygiene, maybe immobile and expressionless.