Life presents each of us with a spectrum of experiences for which we may develop an emotional response. On the high end we may feel excited, energetic and even euphoric, and at the low end we may experience deep sadness, lethargy and despair.

If you are experiencing emotions at the low end of this spectrum, this may be normal depending upon the recent stressful events in your life. Our life experience at one time or another will present each of us with stresses and may leave us feeling emotionally down or luxuriating in a bit of self-pity. When low emotions seem out of proportion to a recent life stress then there may be a cause for concern about depression.

Depression may come in various forms, but most mental health experts say that depression is either reactive (also called situational) or endogenous. Reactive depression events i.e. the death of a loved one, divorce or a physical illness. A person with reactive depression may feel anxious, have difficulty sleeping, and avoid friends and family. The good news is that reactive depression resolves, or the grief from it is dulled by time, the person usually begins to feel better. Endogenous depression may result from reactive depression that has gone untreated. Unlike reactive depression, endogenous depression seems to stem from an internal source rather than from external events. If your world seems gray and you persistently feel sad, frustrated, pessimistic, or experience feelings of guilt, shame, despair and hopelessness, these may be symptoms that warrant further evaluation by your physician. Your physician will be able to help you determine whether you are experiencing one of life's normal dips or more serious depression.

There are several factors that may increase your risks for experiencing clinical depression. Family history is a risk factor as sometimes depression seems to run in families. A personal history of depression may increase your risks as it is not uncommon for depression to recur. Chronic medical conditions that result in pain and frustration as well as changes in body chemistry may cause depression. Personal loss including death, divorce, job loss or even a child going away to college or moving away may precipitate depression. Certain personality traits associated with a tendency to brood, criticize or be pessimistic, are more prone to depression. Alcohol abuse and illicit drug use as well as prescription medicines may alter the normal balance of our sensitive emotional systems and induce depression. And believe it or not, reduced exposure to sunlight may cause seasonal depression. This is more common during the winter months, especially in the higher latitudes where the number of daylight hours is relatively short.

Although depression can occur at any age, it most commonly occurs between the ages of 25 and 45. It is estimated that more than 17 million adults in the United States (one of every seven people) each year suffer some type of depressive illness. It is twice as more likely in women than in men.

If you have been experiencing fatigue unrelated to exertion, mood swings, feelings of sadness, guilt, feelings of resentment, anger, or if you have experienced weight loss or gain, insomnia, memory problems, you should see your physician immediately. A lag in diagnosis and treatment could prove deadly as the No. 1 cause of suicide in the United States is untreated depression.

World Wide Web resources

The National Depressive and Manic-Depressive Association

http://www.ndmda.org

The National Depressive and Manic-Depressive Association's home page is full of helpful information from education to advocacy to support.

Depression.com

http://www.depression.com/types/types_01_normal.htm

This Web site provides information on the various types of depression, as well as antidepressant therapy options.

Dr. Scott Gibbs is a neurosurgeon and editor-in-chief of Mosby's Medical Surfari. You may e-mail questions to him at drgibbs@semissourian.com or write in care of the Southeast Missourian, P.O. Box 699, Cape Girardeau, Mo., 63701.