Are subsyndromal symptomatic depression and major depressive disorder distinct disorders?

Abstract

Depressive conditions that do not meet full symptomatic or duration criteria for a major depressive disorder (MDD) are of considerable interest to both clinicians and researchers. [1-4] The fourth edition of the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) provides descriptions of several types of subthreshold depressive states including dysthymia, minor depression and recurrent brief depression; but many individuals with subthreshold depression and associated impaired functioning do not meet DSM-IV diagnostic criteria for any of these disorders. [3] To cover these cases Judd and colleagues [4] proposed the concept of ‘Subsyndromal Symptomatic Depression’ (SSD) for individuals without depressed affect or anhedonia who have two or more (but less than five) of the other seven symptoms of depression that have been present for most of the time for at least two weeks and that are associated with impaired social functioning. [3,4] The appropriate diagnosis and treatment of individuals with this type of subthreshold depression will require a better understanding of the relationship between SSD and MDD. Are they independent disorders or is SSD a transitional state on the road to MDD? SSD is a relatively common condition. Based on the Epidemiological Catchment Area study in the United States, Judd and colleagues estimated a 12-month prevalence of SSD of 8.4% in the general population; the prevalence in women was double that in men and was particularly high in women who were unmarried and unemployed. [5] A study in Australia reported a 12.9% prevalence in the general population and found that the quality of life for persons with SDD was intermediate, between that for persons without any depressive symptoms and that for persons who met criteria for MDD. [6] A survey of people aged 60 and above in Singapore found that SSD was more common in individuals with a lower socioeconomic status and was often associated with cognitive impairment, anxiety, poor physical health, and poor social functioning. [7] The clinical presentation of SSD is similar to that for other types of depressive disorders. [5] Common symptoms include sleep disturbances (44.7%), prolonged fatigue (42.1%), repetitive thoughts of death (31%), and difficulty concentrating (22.7%). Atypical symptoms such as weight gain, slowed thinking and hypersomnia are somewhat more common in individuals with SSD than in those with minor depression. Risk of suicide is lower among SSD patients than in patients with minor depression or major depressive disorder. [5]