Elderly patients with lesser versions of depression, a group many times larger than those with major depression, are more than five times as likely as healthy patients to descend into major depression within one year, according to a study published in the Annals of Internal Medicine. 

The study's authors believe that perhaps millions of elderly patients who do not meet the criteria for a diagnosis of major depression are indeed depressed, suffering and not being treated for it. Researchers are focusing on depression in elderly patients because the number of persons aged 65 years or older (about 36 million) is expected to double in the next 25 years, with a third of them expected to struggle with a mental disorder at some point. While major depression among the elderly is an important problem, it has overshadowed related disorders that are less serious, but that leave many more people with suffering from painful emotions, disinterest in their surroundings, and thoughts of worthlessness. 

As a result, this group is more functionally disabled, less able to feed and groom themselves, or to go shopping. The current study is the first to carefully reexamine the definitions of certain depression types in older patients seen in primary care settings, and to compare outcomes in different types of depression. According to the Diagnostic and Statistical Manual for Mental Disorders 4th Edition (DSM-IV), minor depression is officially defined using the exact same symptoms as major depression, but including fewer of them. To be precise, persons suffering from minor depression experience 2 to 4 symptoms of depression for most of the day nearly every day, while those with major depression experience five or more symptoms.

Patients with the same symptoms, but experiencing them less frequently - perhaps only several days per week, or for only a few hours each day -- fall within the "subsyndromal" depression category. Among patients in the current study, 20 percent were found to meet the criteria for minor or subsyndromal depression, compared to just five percent that met the definition of major depression. Projecting the percentages out to the U.S. population over aged 65, researchers estimate that about 7 million experience minor or subsyndromal depression, often undiagnosed and untreated, compared to 1.75 million senior citizens with major or so-called clinical depression. "Our study makes the point that the lines drawn between major and minor depression, while useful in some ways, are arbitrary, and may need to be redrawn to put an end to a great deal of suffering in this country," said Jeffrey M. Lyness, M.D., director of the Program in Geriatrics and Neuropsychiatry at the University of Rochester Medical Center, and lead author of the article. "The less severe the depression, the less it has been studied, regardless of how significant its impact might be." 

The current study followed 622 patients who were at least 60 years of age and came in for treatment in primary care practices in greater New York City, Philadelphia and Pittsburgh. The current study sought to measure minor depression, not by studying patients that report to psychiatrist's office, but instead by measuring depression among those who visited their primary care doctors' offices. 

Most elderly persons never see mental a health specialist, but instead may tell their primary care physician about feeling down or nervous or otherwise unwell during a regular check-up. Of the 441(70.9%) patients who completed one year of follow-up, 122 had major depression, 205 had minor or subsyndromal depression, and 114 did not have depression at the beginning of the study. One year after a baseline evaluation, data were collected using standard questionnaires and measurements of depression (e.g., Hamilton Depression Rating Scale).

The study found that patients with minor or subsyndromal depression were five and one-half times more likely to be diagnosed with major depression within a year than those who were not depressed at the start of the study. The group with minor and subsyndromal depression also suffered greater functional disability at one year than patients without depression, although not as severe as those with major depression. As shown in other studies, the level of a patient's medical illness to start with (medical burden) and patients' beliefs about their health and support from others such as families or friends were significant, independent predictors of depression outcome.

Lyness has also co-authored a separate study, now in press in The American Journal of Psychiatry, which may hold part of the answer for these oft-neglected patients with minor and subsyndromal depression. In short, the second study, a statistical analysis of previously published clinical studies, found that patients with less severe forms of depression may on average experience 40 percent more improvement from psychotherapy (i.e., counseling) than from treatment with antidepressant drugs. In addition, a greater proportion of patients receiving psychotherapy improved than did those receiving drug treatment, Lyness said. "There is an urgent need for all of us in the field to redraw the definitions and standards in minor and subsyndromal depression, but that will not happen until we prove what works for these patients in particular, as opposed to what works for patients with major depression," Lyness said. "In the near future we will seek to identify those patients most in need and most likely to respond to specific therapy or medications. To do so, my colleagues and I are currently analyzing information collected over the past five years from over 750 older persons in the Rochester area."