The term "depression" covers the whole range of negative human experience from “feeling blue” to terrifying anxiety and suicidal despair, as well as physical symptoms ranging from flu-like aches and pains to a sense of profound tiredness.
Depression tends to leave people feeling very cut off from the rest of humanity. The stigma which traditionally surrounds “mental illness” makes the sense of misery even worse and stops many people from seeking help. But depression is not anyone’s fault; it is a recognized illness which can be effectively treated in a whole range of ways.
And as befits a complex condition, depression has a range of causes as wide as life itself. Stressful events which cause a deep sense of loss – such as bereavement, divorce, physical illness or the loss of a job – can trigger depression. Some people believe that bottled-up anger and frustration also turn into depression.
Chemistry also has a part to play in depression: when you feel very low, chances are that your brain is lacking in vital nerve messengers called neurotransmitters, although whether this is cause or effect is not clear. Similarly, hormonal changes (as women with P.M.S. know all too well) can make us feel depressed.