Depression is the most common form of mental illness, causing typical symptoms of feeling down, being unable to experience joy, and losing interest in life. The disorder can range from mild to severe and, in the most serious cases, what is called psychosis can occur. Psychosis is a condition where people have beliefs which are not true, and which are not shared by others. There may also be experiences of seeing and hearing things which are not actually there, or, in rarer cases, unreal experiences may involve the senses of smell, taste and touch. When depression and psychosis occur together, this is a sign of serious illness, with a risk of suicide, and treatment is generally commenced urgently, beginning with a combination of medication and psychological therapy.
Different types of psychosis are known to exist and these often fit with a person's mood. In depression there is a low mood, so delusions may center around physical deterioration, for example. This differs from a manic psychosis, where the mood is uplifted and a person can appear euphoric, with delusions of grandeur. In the case of psychosis and schizophrenia, there may be what is known as a paranoid psychosis, in which there may be delusions relating to conspiracies or being persecuted.
Certain illnesses which are particularly associated with depression may cause what is called an organic psychosis in their own right. For example, Alzheimer's and psychosis often occur together, but a person may have depression at the same time. Psychosis and depression may also be experienced by a person with Parkinson's disease. In such cases it can be difficult to say if a person's psychosis is due to the depression itself or is part of the physical illness. Depending on the cause, psychosis treatment may involve just relieving the depression or it may be more bound up with the underlying disease.
With depression and psychosis, there is a danger that hallucinations may occur in which people hear critical voices discussing them. This could feed back and increase existing feelings of worthlessness. In extreme cases, voices may be heard ordering people to harm or even kill themselves. For these reasons, treatment of severe depression is usually started urgently, as the risk of suicide is high.
Antidepressant and antipsychotic drugs are typically combined to treat depression and psychosis, together with intensive non-drug therapy such as cognitive behavioral therapy. A psychiatrist is usually involved in the treatment of people who have both depression and psychosis symptoms. Electroconvulsive therapy, or ECT, where a person is put to sleep and given electric shocks, is reserved for extreme cases where other treatments have not worked, and it has been found to help some people with severe depression.
