NEW YORK: Depression is the number one cause of disability in the world and the 11th leading cause of death among adults. And it is especially prevalent among women, striking up to one out of five over the age of 18.

Two decades ago, prevailing medical opinion held that depression was more of a psychiatric disorder - anger turned inward or a reaction to loss - than an organic brain disease. But recent studies suggest that it may involve brain pathology akin to Parkinson’s or Alzheimer’s diseases.

Brain scans reveal that sections of the frontal cerebral cortex related to mood, as well as the hippocampus, a structure crucial for forming short-term memories, are abnormally small in people who have suffered major depressive episodes. One possibility is that people prone to depression (there is a strong genetic component to the disease) are born with a less-than- normal amount of brain tissue in the affected regions.

Another explanation, supported by a growing body of research, is that depressive individuals react to stress by secreting excessive levels of stress hormones, such as cortical, that are toxic to neurons in high dosages. According to this theory, clinical depression may occur when acute or prolonged exposure to stress hormones damages mood centres in the brain.

In other words, if you have experienced either acute or chronic stress-trauma you may be at elevated risk for depression. But the symptoms are not always obvious, and people in the throes of depression often attribute their suffering more to external than internal causes.

You should ask yourself if you have experienced any of the symptoms on the following list every day or nearly every day during a two-week period: difficulty concentrating; loss of interest in activities you normally enjoy; change in appetite or weight; insomnia or oversleeping; feelings of sadness; physical slowing, agitation or anxiety; feelings of worthlessness or inappropriate guilt and persistent thoughts of death or suicide.

Five or more “yes” answers suggest that you have had a major depressive episode, making you a candidate for treatment. If depression strikes you or someone close to you, the good news is that medication and psychotherapy are more than 80 per cent effective as treatments.

New therapies, including noninvasive magnetic stimulation of underactive mood centres in the frontal lobes and drugs that block the harmful effects of stress hormones, show promise for alleviating depression in patients who do not respond to other treatments. So there is more reason now than ever to seek help. —Dawn/NYT News Service (c) The New York Times.