Depression rates have been growing continuously every year. More and more are affected by this disease, and people are finding it increasingly difficult to cope with certain conditions of life times. The question that many wonder is, what has caused depression to become so common?
Theories vary between Psychologists, Neurobiologists and evolutionary biologist.

A depressive disorder is an illness that influences the body, thoughts and mood. It affects how people eat, sleep, feel about themselves and how they think about things. The symptoms of depression vary from case to case. Symptoms include feelings of hopelessness, pessimism, guilt, decreased energy, fatigue, loss of appetite or over eating, thoughts of death or suicide ,etc. Those who are depressed lose interest in hobbies and activities that were once enjoyed.

An episode of depression associated with a loss of loved ones may differ than depression from a loss of resources. Sub-optimal conditions may play a role in the onset of depression and they may manipulate instant clinical manifestations in their course. Some traits may not be influenced during increasing severity. Even though some qualities are thought to be adaptive, they may in fact increase the chances of depression. Evolutionary systems that compete for recognition may explain much of the clinical "noise" of depression that is overlooked.
Depending upon the number and severity of the symptoms, a depressive episode may be specified as Mild, Moderate or Severe. A Mild depressive episode is when a person has two or three of the above symptoms are usually present. The person is usually distressed by these, but will probably to be able to continue with most activities. The Moderate depressive episode is when a person has four or more of the above symptoms are usually present and the person is likely to have great difficulty in continuing with ordinary activities. The Severe depressive episode is an episode in which several of the above the symptoms are marked and distressing, typically loss of self-esteem and ideas of worthlessness or guilt. Suicidal thoughts and acts are common. 1 Depression statistics that are available from past to current years do not correctly indicate real or actual numbers in the total population. This is because of misdiagnosis, which occurs between
30 and 50 percent of the time and because only half of all depression cases are actually documented. Available statistics are based on those cases in which patients seek care and/or are discovered to have the illness through surveys and studies. In 1998 depressive disorders concerned an estimated 9.5 percent of American adults ages eighteen and over, approximately
18.8 million people. In 2000, it was found that nearly twice as many women 12%, as men, 7%, have a depressive disorder each year. Ten percent of Americans suffer from clinical depression.
Twelve million women in the United States experience an episode of depression every year.
Overall, one in every eight women develops depression at one time in their life. Depression is also becoming more common in adolescents and children. As many as 1 in every 33 children experience this invisible disease. Teenage girls are more likely to acquire depression than teenage boys. one in eight adolescents may have depression. Major depression is found to be most common in the mid to late twenties.

Neurobiologists and psychologists argue whether ego-detrimental experiences and self- depreciating thoughts or biological, and chemical processes are the causes of depression. Genetic researchers have put forth great effort in the past twenty years trying to recognize the genes that are linked to depression. So far, these genes have escaped discovery. This may be due to the fact