The word 'depression' is often used to describe the feelings of sadness which all of us experience at some stage in our lives. It is a term used to describe a form of mental illness called clinical depression.
There are differences between sadness in daily life and the symptoms of clinical depression.

What are the main types of depressive illness?

Adjustment disorder with depressed mood
People with this illness are reacting to distressing situations in their lives (eg the failure of a close relationship or loss of a job) but to a greater degree than is usual.

This depression is more intense than the unhappiness experienced in daily life, it lasts longer and the symptoms often include anxiety, poor sleep and loss of appetite.

The time which this form of depression lasts may vary from weeks to years.

It usually goes away when the cause is removed or when the person finds a new way to cope with the stress. Many people require intensive professional treatment to overcome this type of depression.

Post-natal depression
The so-called 'baby blues' affect about half of all new mothers. They feel mildly depressed, anxious, tense or unwell, and may have difficulty sleeping even though they are tired and lethargic most of the time. This type of depression may last only hours or a few days, then disappear.

However, in about 10 percent of mothers this feeling of sadness develops into a serious disorder called post-natal depression. Mothers with this illness find it increasingly difficult to cope with the demands of everyday life.

They can experience anxiety, fear, despondency and sadness. Some mothers have panic attacks or become tense and irritable. There may be a change in appetite and sleep patterns.

A severe, but rare form of post-natal depression is called puerperal psychosis. The woman is unable to cope with her everyday life and can be disturbed in her thinking and behaviour.

Depressive episode
This is, in general, a more severe form of clinical depression. It can come on without apparent cause, although in some cases a distressing event might trigger the condition.

The cause is not well understood but is believed to be associated with a chemical imbalance in the central parts of the brain. A depressive episode can develop in people who have coped well with life, who are good at their work and happy in family and social relationships.

They become low-spirited, lose their enjoyment of life and suffer disturbed sleep patterns. People experiencing a depressive episode lose their appetite, lack concentration and energy and may lose weight. Feelings of guilt are also common.

Sometimes their feelings of hopelessness and despair can lead to thoughts of suicide.

The most serious form of this type of depression is called psychotic depression. During this illness, the person loses touch with reality, may stop eating and drinking and may hear voices saying they are wicked or worthless and deserve to be punished.

Bipolar Mood Disorder
(previously called Manic Depression) See Bipolar Mood Disorder

What causes Depression?

Often there are many interrelated factors associated with depression:

Heredity
It is well established that the tendency to develop depression runs in families. This is similar to a predisposition...

Biochemical Imbalance
As already stated, depressive episodes are thought to...

Stress
Depression is associated with stress after personal tragedies or disasters. It is more common at certain stages of life, such as at childbirth, menopause and retirement, and common in young adults, women and people with physical health problems.

Personality
People with certain personality characteristics are more prone to depression.

Depression occurs more commonly in people who are sensitive, emotional and prone to experience feelings which are upsetting to them.

Perfectionists who set high standards for themselves and others, and who find it difficult to adjust their ideas and standards to changing circumstances, are often easily depressed. Also, those who are very dependent on others are susceptible to depression if they are let down.

Learnt response
In some cases, people exposed to repeated losses or stress throughout their lives lose their optimism and feel helpless and depressed.

Since 1995, Christos Pantelis, Paul Maruff, Mike Kyrios and Warrick Brewer of the Mental Health Research Institute have worked on a series of functional neuroimaging studies examining differences in patterns of brain activation in schizophrenia, obsessive-compulsive disorder, depression, and first-episode psychosis.

People experiencing feelings of sadness which have persisted for a long time or which are affecting their life to a great extent, should contact their family doctor or community health centre.

Modern treatments for depression can help the person return to more normal feelings and enjoy life. Treatment depends on each person's symptoms, but will take one or more of the following forms:

• Psychological interventions help individuals understand their thoughts, behaviours and interpersonal relationships.
• General supportive counselling assists people to sort out practical problems and conflicts and helps them understand the reasons for their depression
• Anti-depressant medications relieve depressed feelings, restore normal sleep patterns and appetite and reduce anxiety. Unlike tranquillisers, anti-depressant medications are not addictive. They slowly return the balance of neurotransmitters in the brain, taking 1-4 weeks to achieve their positive effects.