Background. Depressive syndromes not fulfilling the criteria for specified disorders (subthreshold depression, SD) may be clinically important. We aimed to study SD in old and very old age, in comparison with subjects with no depressive symptoms (NDS) and subjects with major depression (MD).

Methods. A community-based random sample of 516 subjects, age 70 to 100 years and over, stratified by age and sex, was examined. All participants were investigated by psychiatrists and by geriatricians independently.

Results. In 16·5% (N = 85) of the study subjects SD was identified. Study subjects with SD had, similarly to the subjects with MD, significantly more somatic diagnoses and used more somatic as well as psychotropic medications than the subjects with NDS. Self-ratings and observer ratings of depression indicated that SD was a milder depressive state than MD.

Conclusions. Compared with MD, SD is probably a milder form of depression. The increased use of psychotropic medications indicates that at least a portion of these individuals have a disorder requiring treatment. One of the characteristics of SD is co-morbidity with somatic illnesses and physical disability.