Depression can be a serious illness. Health professionals tend to use the terms 'depression', 'depressive illness' or clinical depression to refer to something very different from the common experience of feeling miserable or fed up for a short period of time.
Depression is common; about 15 percent of people will have a bout of major depression at some point in their lives and it is the fourth most common cause of disability worldwide. The number of people with depression is hard to estimate, because many don't get help or aren't formally diagnosed.
Most of the 4,000 suicides committed each year in England are linked to depression. On average, 15% of people with recurrent depression (repeated attacks) have an increased risk of suicide.
Women seem to be twice as likely to suffer from depression than men, although this could possibly be because men may be less likely to seek help. Depression can appear at any age and occurs in every Western country. There is some debate about whether it is seen in every culture across the world, although it now seems likely that depression is a universal human condition.
People with a family history of depression are more likely to experience depression themselves. Depression affects people in many different ways and can cause a wide variety of physical, psychological (mental) and social symptoms.
Doctors describe depression in the following three ways:
1. By how serious it is:
2. By physical symptoms: If you have depression you will probably have one or two (or maybe more) physical ('somatic') symptoms.
3. By psychotic symptoms: If you have depression you may also have psychotic symptoms, such as hallucinations or delusions. These symptoms don't affect everyone with depression. Please see the separate encyclopaedia topics on specific types of depression such as bi-polar affective disorder, and seasonal affective disorder (SAD) for further information.
If you think you have depression you should visit your GP. Your GP may do a physical check and do some blood or urine tests to rule out other conditions.
There are no clinical tests for depression so detailed interviews and questionnaires are used in the diagnosis.
There are many different questionnaires used to measure depression. However two classifications of mental illness are most widely used. The first, developed by the American Psychiatric Association, is called the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The second, developed by the World Health Organisation, is called the International Classification of Diseases - Part 10 (ICD10).
Using one of these guidelines, it is usually possible for your GP to diagnose depression, decide which type of depression you are experiencing and to rule out another mental conditions.
About half of the people who have a first episode of depression will have another episode within 10 years. The risk of further bouts of depression is higher than in someone who has never been depressed.
Mental disorders (particularly depression and substance abuse) are associated with more than 90% of all cases of suicide.