Research report
A tune in “a minor” can “b major”: A review of epidemiology, illness course, and public health implications of subthreshold depression in older adults

https://doi.org/10.1016/j.jad.2010.09.015Get rights and content

Abstract

Background

With emphasis on dimensional aspects of psychopathology in development of the upcoming DSM-V, we systematically review data on epidemiology, illness course, risk factors for, and consequences of late-life depressive syndromes not meeting DSM-IV-TR criteria for major depression or dysthymia. We termed these syndromes subthreshold depression, including minor depression and subsyndromal depression.

Methods

We searched PubMed (1980–Jan 2010) using the terms: subsyndromal depression, subthreshold depression, and minor depression in combination with elderly, geriatric, older adult, and late-life. Data were extracted from 181 studies of late-life subthreshold depression.

Results

In older adults subthreshold depression was generally at least 2–3 times more prevalent (median community point prevalence 9.8%) than major depression. Prevalence of subthreshold depression was lower in community settings versus primary care and highest in long-term care settings. Approximately 8–10% of older persons with subthreshold depression developed major depression per year. The course of late-life subthreshold depression was more favorable than that of late-life major depression, but far from benign, with a median remission rate to non-depressed status of only 27% after ≥ 1 year. Prominent risk factors included female gender, medical burden, disability, and low social support; consequences included increased disability, greater healthcare utilization, and increased suicidal ideation.

Limitations

Heterogeneity of the data, especially related to definitions of subthreshold depression limit our ability to conduct meta-analysis.

Conclusions

The high prevalence and associated adverse health outcomes of late-life subthreshold depression indicate the major public health significance of this condition and suggest a need for further research on its neurobiology and treatment. Such efforts could potentially lead to prevention of considerable morbidity for the growing number of older adults.

Introduction

With the introduction of the DSM-III, psychiatry increased reliability of its diagnoses, including major depressive disorder (MDD) (Judd et al., 1994). The establishment of boundaries at which the frequency, duration, or severity of symptoms crossed a “threshold” sufficient to be labeled psychopathology was not simple, however. When possible, thresholds were based on empirical data, but otherwise, non-empirical “expert opinion” was involved in separating the “ill” from the “well.” With emphasis on dimensional aspects of psychopathology in development of the upcoming DSM-V, now may be an opportune time to explore the merits of better defining various continua of disorders such as depression. Subthreshold depression (SubD) has sometimes been divided into distinct categories (e.g. minor depression [MinD], recurrent brief depression, and subsyndromal depression [SSD]), but at other times studied as a single entity. Based on the diagnostic criteria used in studies, overlap among these constructs is common. We exclude dysthymia (DYS) as a type of SubD because it has well-defined DSM-IV-TR (First et al., 2002) criteria, and most SubD studies do not include it.

In 1992, Wells et al. (1989) reported that depressive symptoms not qualifying as MDD were associated with more social disability than many medical illnesses. Soon thereafter, Judd et al. (1994), in analyses from the Epidemiological Catchment Area (ECA) study (1982), reported a one-month prevalence of SSD in the general adult population of 11.8%. DSM-IV later listed criteria for MinD among its research diagnostic criteria in the section on Depression Not Otherwise Specified. These were similar to those for MDD except requiring only 2–4 symptoms and no prior history of MDD; however, subsequent research has shown that DSM-defined MinD misses a substantial number of people who suffer morbidity from other variants of SubD. For instance, Judd et al. noted that among the SubD subjects in the ECA study, less than a third met criteria for MinD because neither depressed mood nor anhedonia (MDD Criterion A symptoms) were present (Judd et al., 1994). The investigators found virtually no differences between SubD subjects with versus without Criterion A symptoms. Angst et al. (1990) proposed another variant of SubD—recurrent brief depression, in which the only reason for failing to meet MDD criteria was that symptoms did not persist uninterrupted for two consecutive weeks.

Despite variable definitions and criteria, “non-major” depressions consistently exact major consequences on affected individuals (e.g. increased disability, poorer quality of life) and on society (e.g. increased healthcare costs) (Broadhead et al., 1990, Hybels et al., 2001, Sptizer et al., 1995, Xavier et al., 2002, Koenig, 1998). The concept of SubD resonated strongly in geriatric psychiatry (Jeste et al., 1999, Jeste et al., 2005), along with a speculation that MDD prevalence among older adults was inaccurate in the ECA study because of diagnostic ascertainment procedures (Judd and Akiskal, 2002). Re-analyzing the ECA data, Judd and Kunovac (1998) found that among adults ≥ 65 years old, SubD (MinD + SSD) prevalence was 31.1%, versus 6.3% for MDD—a fivefold difference.

Given the preponderance of SubD compared to MDD in older adults and the increasing research on late-life SubD, we believe an updated review of SubD in older adults is warranted. Specifically, we focus on the following aspects of late-life SubD, for which we know of no recently published comprehensive review: epidemiology, longitudinal time course, risk factors and public health consequences.

Section snippets

Methods

We searched PubMed (1980–January 2010) using combinations of the following search terms: Group (A) subsyndromal depression, subthreshold depression, and minor depression with Group (B) elderly, geriatric, late-life, and older adult. Additional articles were identified via manual review of references in articles from database searches. We extracted data from articles in English conducted among older adults (age  55 years) that focused on any depressive condition with proposed criteria other than

Results

We identified 153 unique, potentially relevant articles by database searches (Fig. 1). Although we used search terms geriatric, older adult, and late life for thoroughness, these terms yielded no articles other than those discovered with the search term elderly, hence the omission of these other search terms in Fig. 1. An additional 28 studies of interest were identified via manual review of database-generated articles.

Discussion

The evidence reviewed above strongly suggests that late-life SubD, howsoever defined, is prevalent, worsens quality of life and health of older adults, and impacts healthcare systems via increased service utilization and cost expenditure. Epidemiological research on late-life SubD demonstrated a pattern observed in late-life MDD: increasing prevalence moving from community to PC to LTC settings (community [10%], PC [25%], medical inpatients [30%+], LTC [c. 45–50%]). SubD was consistently at

Role of funding source

This work was supported in part by grants from the National Institute on Mental Health (P30 MH080002), the National Institute on Aging (T35 AG26757), and The US Health Resources and Services Administration (Geriatric Academic Career Award), the UCSD Sam and Rose Stein Institute for Research on Aging, the John A. Hartford Center of Excellence in Geriatric Psychiatry, and the Department of Veterans Affairs.

Conflict of interest

Dr. Lavretsky has a research grant from the Forest research Institute.

AstraZeneca, Bristol-Myers Squibb, Eli Lilly, and Janssen donate medication to Dr. Jeste's NIMH-funded research grant, “Metabolic Effects of Newer Antipsychotics in Older Pts.”

No other authors have any conflicts of interest.

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