One in a hundred people suffer from schizophrenia which affects the mental functioning of a person and in the long term may cause changes to a person's personality.

First onset is usually in adolescence or early adulthood. It can develop in older people, but this is not common.

Some people may experience only one or more brief episodes in their lives. Others may suffer recurring or life long schizophrenia.

What are the symptoms of Schizophrenia?

Delusions - false beliefs of persecution, guilt or grandeur or being under outside control. People with schizophrenia may describe plots against them or think they have special powers and gifts.

Hallucinations - most commonly involving hearing voices. Other less common experiences can include seeing, feeling, tasting or smelling things which to the person are real but which are not actually there.

Thought disorder - where the speech may be difficult to follow; for example, jumping from one subject to another with no logical connection. Thoughts and speech may be jumbled and disjointed. The person may think someone is interfering with their mind.

Loss of drive - where often the ability to engage in everyday activities such as washing and cooking is lost. This lack of drive, initiative or motivation is part of the illness and is not laziness.

Blunted expressions of emotions - where the ability to express emotion is greatly reduced and is often accompanied by a lack of response or an inappropriate response to external events such as happy or sad occasions.

Social withdrawal - this may be caused by a number of factors including the fear that someone is going to harm them, or a fear of interacting with others because of a loss of social skills.

Lack of insight or awareness of other conditions - because some experiences such as delusions and hallucinations are so real, it is common for people with schizophrenia to be unaware they are ill. For this and other reasons such as medication side-effects, they may refuse to accept treatment which could be essential for their well-being.

Thinking difficulties - a person's concentration, memory, and ability to plan and organise may be affected, making it more difficult to reason, communicate, and complete daily tasks.

What causes Schizophrenia?

No single cause has been identified, but several factors are believed to contribute to the onset of schizophrenia in some people:

Genetic factors
A predisposition to schizophrenia can ruin families. In the general population, only 1 percent of people develop it over their lifetime. If one parent suffers from schizophrenia, the children have a 10 percent chance of developing the condition - and a 90 percent chance of not developing it.

Biochemical factors
Certain biochemical substances in the brain are believed to be involved in this condition, especially a neurotransmitter called dopamine. One likely cause of this chemical imbalance is the person's genetic predisposition to the illness.

Family relationship
No evidence has been found to support the suggestion that family relationships cause the illness. However, some people with schizophrenia are sensitive to any family tension which, for them, may be associated with relapses.

Environment
It is well recognised that stressful incidents often precede the onset of schizophrenia. They often act as precipitating events in vulnerable people. People with schizophrenia often become anxious, irritable and unable to concentrate before any acute symptoms are evident. This can cause relationships to deteriorate, possibly leading to divorce or unemployment. Often these factors are blamed for the onset of illness when, in fact, the illness itself has caused the crisis. It is not, therefore, always clear whether stress is a cause or a result of illness.

Drug Use
The use of some drugs, especially cannabis and LSD, is likely to cause a relapse in schizophrenia.