Minor depression is a greater risk factor for an episode of Major Depression than most medical illnesses, according to the results of a study presented Friday at the 113th Annual Convention of the American Psychological Association in Washington, DC.

After accounting for other potential risk factors, such as demographic factors and medical illnesses, having minor depression increases the risk of having an episode of major depression over a 15-year period by six-fold, said co-investigator Dr. Joshua Fogel.

“Minor depression” can be defined as having two to five depressive symptoms over a period of several weeks, the researcher pointed out, whereas “Dysthymia,” which is characterized by moods that are consistently low, but not as extreme as other types of Depression, involves depressive symptoms lasting 2 years or longer.

Fogel, from Brooklyn College of the City University of New York, and Dr. Daniel E. Ford, of Johns Hopkins University in Baltimore, evaluated data from the Baltimore Epidemiological Catchment Study.

At the start of the study, 101 of the 1634 subjects examined (19 percent) were diagnosed with minor depression, 19 of whom developed major depression during 15 years of follow-up.

Although medical illnesses, such as Heart disease  and Diabetes, have been associated with Depression, only minor depression and stroke were associated with major depression in this study, Fogel noted. The risk of major depression was increased ten-fold among Stroke patients.

“It’s important that when people are experiencing symptoms related to depression that persist for more than a few weeks, not related to bereavement, they should consider treatment,” Fogel said. “If they don’t take care of it, there’s the possibility that it can turn into something much worse.”

Rather than medication for minor depression, he advocates psychotherapy or other measures, such as reading self-help books.