While this isn’t an exhaustive list, here is a quick overview of the most common forms of depression.

Mild/Minor Depression is the least severe form of depression. Usually the symptoms aren’t so severe that they have a major impact in the life of the sufferer, although the depression can still cause distress and disruption. Many people who are suffering from mild depression never seek treatment – they don’t believe the symptoms are severe enough.

Dysthymic Disorder is a long-term form of mild depression (lasting two or more years). Like mild depression, most sufferers never seek help as they don’t believe their symptoms are severe enough. Also like mild depression, the symptoms of dysthymic depression don’t usually have a huge impact on the sufferers day-to-day life. But when the long-term results from the depression are considered, the impact can be huge. People who suffer from dysthymic depression often can’t remember a time when they weren’t depressed.

Moderate Depression fits somewhere between mild depression and major depression. The symptoms of moderate depression are more severe and numerous than mild depression, and they begin to have an impact on the work, home and social life of the sufferer. While mild depression and dysthymic depression can go unnoticed by others, the symptoms of moderate depression are usually noticeable. If left untreated, people suffering from moderate depression can slip into major depression.

Major Depression (also known as clinical or unipolar depression) is what most people think of when they think of depression – the individual seems to have totally given up on life, and has a large number of obvious symptoms. It is unlikely that someone suffering from major depression could function normally in a work, social or home setting – their symptoms are too pronounced. Suicide can be a huge risk with major depression, and professional help needs to be sought to treat the depression.

Bipolar Depression (BPD) is sometimes known as manic-depression, and is characterized by the sufferer having large mood swings from very upbeat and energetic to extreme lows. Both periods normally last for several weeks at a time. Bipolar depression is usually categorized into a number of sub-categories. While there is no firm consensus on how many sub-categories there are, the four most common are Bipolar I Disorder, Bipolar I Disorder, Cyclothymic Disorder and Bipolar NOS.

People with bipolar I disorder have the most extreme mood swings. Their low moods can be classified as major depression, while in their positive moods they can engage in crazy, outrageous and even dangerous activities. During this ‘mania’ state they may even suffer from paranoia or hallucinations.

People with bipolar II disorder have much less extreme mania periods. Indeed, many bipolar II sufferers go untreated because people mistake their ‘mania’ phase for simply getting over their depression. People with bipolar II don’t suffer from paranoia or hallucinations.

Cyclothymic disorder is a milder but much more long-term version of bipolar disorder (usually lasting for two or more years). Like bipolar II the mania phases are relatively minor, but in addition their depressive phases aren’t so severe that they classify as major depression. If left untreated, cyclothymic depression can develop into bipolar II depression.

Finally, Bipolar NOS (Not Otherwise Specified) is a catch-all category for people who have some of the symptoms of bipolar, but those symptoms don’t allow the person to be neatly categorized in one of the three other categories. For example, the sufferer may have fast cycling between the manic and depressive states, or manic states without depressive states.

Premenstrual Dysphoric Disorder (PMDD) is a severe form of Premenstrual Syndrome (PMS) that affects between 3% and 8% of women. Symptoms of depression appear around a week prior to menstruation, and disappear within a few days of menstruation beginning.

Postnatal (Postpartum) Depression can occur any time in the first 12 months after a baby is born. Some form of postnatal depression affects over 80% of new mothers, although most who are affected only have a very mild form of depression that usually passes naturally with rest and the support of family and friends. However around 15% of mothers get a more severe form of postnatal depression, and like major depression the sufferer needs treatment and support to overcome the illness.

Seasonal Affective Disorder (SAD) is a type of depression caused by the changing light levels throughout the year. The most common for of SAD is caused by the low-light levels of winter, but a much rarer form of the disorder is triggered by the high-light levels of summer.

As you can see, depression comes in many different forms – each type of depression has different triggers and symptoms associated with it, and each type of depression also responds better to different treatments. By being aware of the different forms depression can take, you can be much more prepared to help a friend of family member.

One thing that may make it hard for doctors to recognise depression is that people with depression often complain of physical problems, commonly headaches, lethargy, stomach upsets or joint pains, rather than low mood, sometimes because these can be significant symptoms, but sometimes because they find it difficult to admit to feeling emotionally distressed for reasons they may not even be able to identify.

Depression is usually related to upsetting life events, such as bereavement, relationship difficulties, physical illness, or job or money worries.

Are there different types of depression?

Bi-polar disorder (manic depression)

Someone with bi-polar affective disorder has both ‘high’ and ‘low’ mood swings, along with changes in thoughts, emotions and physical health.

Post-natal depression (PND)

About 1 in 10 women experience postnatal depression in the first year after having a baby.

Seasonal Affective Disorder (SAD)

Some people describe feeling depressed regularly at certain times of the year. Usually this kind of depression starts in the autumn or winter, when daylight is reduced.

How can you reduce the risk of depression?

• Keep in touch with you friends. If you are already depressed you find it very difficult to be sociable, and this can make you feel more depressed. So it is important for you to keep in contact with friends and find someone to talk to when you are feeling low.

• Keep active. Being more active is associated with lower levels of depression. Outdoor activity seems to be particularly important in staving off depression in older men.Review your eating habits. Recent research has suggested that people who are depressed may have low levels of certain essential fatty acids, which are found in fish oils. It has therefore been suggested that people with depression should change their eating habits, for example eating more oily fish such as sardines, or should take fish oil supplements.

• Investigate herbal medicine. St John’s Wort ( Hypericum perforatum) can help many people with mild to moderate depression. Before taking St John’s Wort check with your doctor or pharmacist especially if you are taking other kinds of medication, for example for heart disease, epilepsy, asthma or migraine.

• Investigate self-help techniques. Some people have reported benefits from various self help techniques such as meditation, listening to music, and acupuncture.

• Take control. Some people find it helps if they have some control over what happens. This helps to guard against the kind of ‘hopelessness’ which is associated with depression. Activities that involve making a ‘fresh start’ have been shown to help people recover from long-lasting depression. Similarly, learning to set small or manageable goals can give you a sense of achievement and make you feel better.

There are a number of self-help books, guides, and software programmes which can help you to learn ways of coping with mild to moderate episodes of depression.

What treatments are there for depression?

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. These newer drugs are popular because they tend to have fewer side effects than older drugs.

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 antidepressant 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 (cognition). 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.

Electroconvulsive therapy (ECT)

ECT is a controversial treatment which is intended only to be used for people with severe depression who have not responded well to medication or other treatments. The person receiving ECT is given an anaesthetic and drugs to relax their muscles. They then receive an electrical ‘shock’ to the brain, through electrodes placed on the head. Most people are given a series of ECT sessions. Some people say that ECT is very helpful in relieving their depression, although others have reported unpleasant experiences, including memory problems.