• Genetics can be an important factor in depression as it often runs in families for generations.

• Traumatic events and stress can also be a cause for depression. Like the death of someone close to you, the break up of a good friendship, bullying.

• Changes in circumstances - moving home, a new school, parental split, other family problems.

• Physical medical conditions such as terminal or long standing illnesses. Depression can also make underlying conditions worse.

• People who think negatively and a pessimistic personality are at higher risk of developing depression.

• Many psychological conditions can co exist with depression, such as anxiety, substance abuse and eating disorders.

Chemical imbalances in the brain
When someone is suffering from depression there is also a change in the balance of chemicals in the brain called neurotransmitters. These chemicals are responsible for carrying signals in the brain and nerves. Anti- depressants can help to restore these chemicals to their original levels, thus, lifting the mood of the depressed person. Although there is this physical change in the brain it is thought to be a symptom of depression, not a cause.

Treatment usually consists of talking treatments and in some cases antidepressants are also required. Most children respond quickly to treatment and are fully recovered within a year or two.

Drug Treatments
Anti-depressant drugs act by increasing the activity of those brain chemicals, which affect the way we feel. Anti-depressants are thought to help 2 out of 3 of people with depression.

Tricyclic antidepressants, such as dothiepin, imipramine, and amitryptyline are often prescribed for moderate to severe depression. These usually take up to two weeks to start working and may have side effects.

Newer antidepressant drugs (SSRIs and SNRIs) target specific chemical 'messengers' in the brain. The most well known SSRI is fluoxetine (Prozac) but there are several other brands.

SSRIs such as Paroxatine (Seroxat) should not be prescribed for children and teenagers under 18 years because new data has shown an increase in self-harm and potentially suicidal behaviour when they are used for the treatment of depressive illness in this age group. Fluoxetine is the only SSRI that may be prescribed for under-18s, but only when specialist advice has been given.

These drugs work by increasing the level of the chemical serotonin in the brain, which helps to alleviate the symptoms of depression.

Lithium carbonate is sometimes prescribed to people with severe depression. High levels of lithium in the blood are dangerous so anyone taking lithium must have regular blood tests.

If you are prescribed drugs for depression you will probably be advised to take them for at least six months - or longer if you have a previous history of depression. You may experience withdrawal effects if you stop taking anti-depressant drugs, particularly if you stop suddenly. These effects can include headache, nausea, dizziness and even hallucinations. Always consult your doctor before stopping taking anti-depressants. Do not stop taking medication suddenly, as the withdrawal effects may be severe.

Talking treatments
Cognitive behavioural therapy (CBT) is a type of 'talking' treatment. It is based on the fact that the way we feel is partly dependent on the way we think about events. It also stresses the importance of behaving in ways which challenge negative thoughts - for example being active to challenge feelings of hopelessness.

Interpersonal therapy (IPT) focuses on people's relationships and on problems such as difficulties in communication, or coping with bereavement. There is some evidence that IPT can be as effective as medication or CBT but more research is needed.

Counselling is a form of therapy in which counsellors help people think about the problems they are experiencing in their lives and find new ways of coping with difficulties. They give support and help people find their own solutions, rather than offering advice or treatment.