What Is Depression?

Depression is a mental illness which involves feelings of intense sadness, hopelessness and low self-esteem which won't go away, along with physical symptoms like sleeplessness, a loss of energy, or physical aches and pains. Depression is different from feeling low, even though people often say "I'm depressed" when they feel a bit down. Mild to moderate depression is common, and while it usually doesn't stop you from doing your normal daily activities, it does make everything harder to do and seem less worthwhile.

Severe depression is extremely distressing and makes normal activity near impossible. It can be life-threatening, since many people with severe depression attempt suicide. Somebody with severe depression might stay in bed for days or weeks on end because they don't have the energy to do anything else. This kind of depression gets you labelled with 'Major Depression' or 'Major Depressive Disorder'. It is also sometimes called 'unipolar' depression, to distinguish it from bipolar depression.

Symptoms
The most common symptoms of depression are:

1. Low mood, which varies little from day to day.
2. Loss of interest, pleasure and concentration
3. Loss of energy, tiredness even after little effort.
4. Loss of appetite, or increased appetite
5. Weight loss when not dieting or weight gain
6. Insomnia & sleeplessness, or excessive sleepiness
7. Visible agitation or slowed movements
8. Feelings of worthlessness, low self-esteem, low self-confidence
9. Excessive or inappropriate feelings of guilt
10. Loss of sex drive
11. Thoughts about suicide or suicide attempts

As a general rule, if you have experienced four or more of these symptoms, for most of the day nearly every day, for over two weeks, then you should seek help. Very severe depression is sometimes also accompanied by psychotic symptoms, like hallucinations or delusions.

Causes
The exact cause of depression is not known, but the likelihood that somebody will decome depressed seems to be determined by a combination of physical, psychological and social factors.

Some types of depression run in families, so it's thought that some people inherit a genetic predisposition for it. In identical twins, if one twin is diagnosed with clinical depression, the other twin has around a 46% chance of developing one too. Other people affected by depression have no family history of mental illness, but they may be vulnerable to depression because they have picked up very negative ways of thinking. Low self-esteem and distorted thinking are closely related to depression, although it's not always clear if they are a cause or an effect.

Depression can be triggered by a traumatic event or period of stress, such as a bereavement, losing a job, family problems, divorce, exam stress, poverty or social isolation. Substance abuse and certain chronic illnesses (e.g. hypothyroidism) also make people more likely to develop depression.

More about depression:

• Bipolar Depression
  
• Other types of Depression
  
• Physiology of Depression
  
• Advice For Friends and Family

Sources:
1. The Depression Alliance - Now We're Talking (April 17, 2007)
2. NPR - History of Treating Depression (2004)
3. Karl Hempel, M.D. - Depression: What you need to know