Depression: 

Depression is a common illness that can be triggered by stressful situations such as financial difficulties, redundancy or death of a very close person.
The illness can be caused by an imbalance of certain chemicals in the brain.
Many people may feel down sometimes, but recognizing depression is not simple. 
Depression doesn’t differentiate between race, sex, income or age. It may develop for a range of reasons and can seriously disrupt people's lives.

Symptoms of Depression 
The symptoms of depression can differ greatly according to the kind of depression. Victims often experience low moods and lose interest and enjoyment in aspects of life. This is often more noticeable to the patients' family and close friends than to themselves. Physically, patients can complain of a variety of conditions like back pain, headaches and giddiness. Behaviorally depression can cause changes in weight and appetite, fatigue, lack of interest in social life and in sex, irritability, anxiety and confusion.
The apathy which accompanies depression often stops sufferers from seeking help.

Treatment of depression 
Fortunately depression can often be successfully treated, either with antidepressant drugs, or with therapy and counseling, or with a combination of both. The treatment that doctors choose depends on a number of factors: such as types of symptoms, lifestyle, severity and being under other medications. Complementary therapies and conditions can also help sufferers to manage depression. Counseling can successfully help sufferers to overcome and deal with a wide range of problems and it may be carried out by a trained counselor, a psychologist or psychotherapist.

Antidepressants
Antidepressant drugs work by affecting the levels of chemicals in the brain, such as serotonin. Antidepressants frequently lift a person's mood and allow him/her to address the problems which caused the depression in the first place. 
An important fact to know is that antidepressant drugs take several weeks to start having a noticeable effect.