Depression is usually classified into severe (or major) and mild (or minor) forms. In the severe form the symptoms are obvious, but the mild form is harder to recognize, and is sometimes termed "sub-threshold". People with major depression have an increased risk of dying from any cause; this has been shown consistently in several studies. Minor depression, on the other hand, has been linked with an increased death rate in some studies, but not in others. This may be because the trials examined a variety of age groups, and people from different social and health backgrounds. A recent Dutch study examined a group of older people, to see if both major and minor depression were associated with an increased risk of dying, independent of health behavior (e.g. smoking, excessive alcohol) and social, health and economic backgrounds.

During a 12-month period over 3,000 people aged 55 to 85 in Amsterdam, Netherlands, were interviewed, and their survival over the next 5 years recorded. Based on their scores at entry using two symptom-rating scales, they were diagnosed as having major depression, minor depression, or no depression.

Deaths were recorded from death certificates, with information on the cause of death obtained from the Dutch Central Bureau of Statistics. Questionnaires were used to get information on participants' socio-economic status, presence of chronic diseases, any physical disability, their health behavior and physical activity.

The average age of participants was 71 years; just over half were women. Out of the 3,000-plus participants, 2% had major depression, 13% had minor depression, and 85% were not depressed. For the most part, those with depression - major or minor - were usually women, less well-educated, lived in cities, had more chronic diseases or were disabled, were inactive, and were smokers, compared with the non-depressed. Major depression occurred more often in younger subjects.

After excluding the effects of socio-economic factors and the presence of chronic diseases, people with major depression were almost twice as likely to die in the 5-year period than non-depressed subjects. This result was significant, even after the allowing for possible effects of overweight, disabilities, smoking and physical inactivity.

People with minor depression also had an almost 2-fold increased risk of dying. After allowing for the effects of sex and age, this risk was reduced, but it was still significant for men, though not for women. As with major depression, the effects of age, education, city-dwelling, chronic disease, and physical disability reduced the risk somewhat, but it was still significant.

Three participants committed suicide - one with minor depression and two without depression at the start of the study. Suicide is a recognized risk in major depression, but there were relatively few people with this severe degree of depression in this study - about 60, compared with about 400 with minor depression and 2,500 without depression.

The differences between risk in men and women with minor depression may be due to several factors - e.g. women's differing physiologic response to stress, or more frequent cardiovascular disease in men.

One must question the cause of the increased risk of dying for those with depression. Possible reasons are that depressed people are less likely to follow their physician's directives for medical treatment, their depression may make them more susceptible to diseases (by decreasing immunity), or that their depression may just be a symptom of a hidden developing disease.

Whatever the cause, the risk appears to be real, and it provides a good reason why depression in older people should be taken seriously and treated energetically.

Source

Minor and major depression and the risk of death in older persons.
BWJH. Penninx, SW. Geerlings, DJH. Deeg, Arch Gen Psychiatry, 1999, vol. 56, pp. 889--895