The concept of depression is broad and encompasses a number of different phenomena. The term is used in the vernacular to refer to a simple "blue" mood. In a medical sense it can label anything from a long-lingering feeling of hollowness to a critical situation ending in a suicide.

The simple "down mood" or "bad hair day" really isn't depression at all. It's merely the experience of normal human emotions in response to external and internal factors. Every case of being sad or lonely is not an example of depression. Low feelings are normal and even healthy. Depression refers to more severe cases where those negative feelings take hold and have a more serious or lasting influence on one's well-being or ability to function.

There are three types of depression, all of which share that similarity. One is known as dysthymia. Dysthymia is a chronic, low-grade depression that lasts over a long period of time. This type of depression is "sneaky" and may not be spotted easily. Its long-lasting nature allows one to "adjust" to its symptoms somewhat, making a depressed mood seem like the normal every day nature of things.

Dysthymia sufferers have the overall quality of their lives undermined by depression, often without realizing it. They may think they are simply dour people or that life is inevitably something less than enjoyable.

Those with dysthymia are able to function with a high degree of normalcy, but are constantly nagged by feelings of sadness, despair, loneliness and related emotions.

Situational depression can have more severe symptoms. This is the form of depression that rears its head in direct response to external circumstances. Any number of traumas or trying events can trigger a bout of situational depression. The death of a loved one, or the loss of a job, for instance, may produce intense and temporarily debilitating depressive symptoms.

The key to differentiating situation depression from its clinical counterpart is the temporary nature of the symptomology and the fact that it can often be traced back to a specific cause. One should note that traumatic events can also herald the onset of clinical depression, however.

Those suffering from situational depression may find life very difficult for a period of time. They may feel agitated or nervous, have disruptions in sleeping habits, or experience other common depressive symptoms. However, the problem usually passes as the individual learns to cope with the problems that triggered the episode.

Clinical depression is more severe. If one experiences symptoms that interfere with regular functioning for a period longer than two weeks in length, they may be suffering from clinical depression. Clinical depression can last indefinitely and can be quite devastating.

The hallmark of clinical depression is the inability to enjoy almost any aspect of life. In some cases, the sufferer may even begin to consider suicide as an alternative to continuing on in their depressed state. Symptoms can run the gamut from a vague sense of unease to utter and complete hopelessness.

Interventions are usually required for one to overcome clinical depression. These can involve the use of psychotherapy, prescription antidepressants and other strategies aimed at solving the problem. Those who do not seek treatment for this condition may find the problem literally fatal in the long run. Fortunately, these methods can often be successful in helping one overcome the dreaded symptoms of clinical depression.

Depression is a growing problem, and as the epidemic continues to grow, it only makes sense for all of us to gain a better understanding of the disease. The World Health Organization posits that by the year 2020 depression will be second most devastating disease facing humanity, second only to heart disease in its impact. Depression touches the lives of most everyone and all of us should develop a stronger appreciation of what separates depression from simply having a "lousy week."

Although the term "depression" may encompass many things in popular use, in a strict sense it refers to one of the three variations mentioned in this article. Dysthymia, situational depression and clinical depression represent the three primary types of depression. They share a great deal in common, but can be differentiated from one another by the severity of their symptoms and their longevity.