Subthreshold Depression in Older Adults: Overview and Expert Interview

Older adults have an elevated risk of depression compared to individuals in other age groups, according to the Centers for Disease Control and Prevention.¹ However, findings suggest that major depressive disorder (MDD) affects a small portion of this population. A 2017 review published in JAMA reported that the prevalence of MDD is 2% among older adults, with an additional 10% to 15% of older adults experiencing significant depressive symptoms.²

Many older persons may have subthreshold depression, defined in the DSM-5 as depressed mood with at least 1 symptom of MDD and the presence of “clinically significant distress or deficit lasting at least 2 weeks.”³ Researchers recommend that subthreshold depression be diagnosed “using a psychiatric interview to establish minor depression, according to DSM-IV, or a depressive episode with insufficient symptoms according to DSM-5.” They also recommend taking into consideration cutoff scores on validated scales, such as the Patient Health Questionnaire (PHQ-9), 30-item Geriatric Depression Scale (GDS-30), 20-item Center for Epidemiologic Studies Depression Scale, or Hamilton Depression Rating Scale.³

Despite substantial heterogeneity, findings from several studies show that at least 10% to 20% of participants with subthreshold depression converted to MDD during a 12-month period, with 1 study showing conversion rates of 28% to 41%.³ Alongside the danger of conversion to MDD, subthreshold depression can exacerbate morbidity and other conditions, such as diabetes, cardiovascular disease, arthritis, and asthma. In a 2013 meta-analysis, the relative risk of mortality was 1.58 in MDD and 1.33 in subthreshold depression,³ underscoring the importance of timely diagnosis and treatment.

“We have to dig deeper if we are considering a diagnosis of mild or subthreshold depression,” said co-author Ivan Aprahamian, MD, MSc, PhD, FACP, an associate professor in the division of geriatrics and psychiatry at the Jundiaí School of Medicine, Brazil. Clinicians must “make sure to exclude important differentials such as dementia, mild cognitive impairment, frailty, and atypical manifestations of somatic diseases,” he told Psychiatry Advisor. Along with organic disease, it is also necessary to distinguish subthreshold depression from sadness secondary to the various life changes that older adults often face, such as retirement or the loss of a loved one.

Brief psychotherapy is currently the first-line treatment. “This approach is especially beneficial in older adults because it allows many psychic aspects and their functioning to be addressed,” as stated in Dr Aprahamian’s paper.³ In the CASPER trial, a 4-month program incorporating psychological support and behavioral interventions, the treatment led to reduced subthreshold depressive symptoms compared to standard treatment.⁴ In a meta-analysis of 7 studies, patients who received a psychotherapeutic intervention showed a 30% lower risk of developing MDD.³

“The prescription of antidepressants is not recommended as first-line treatment or sole intervention for [subthreshold depression] treatment,” and the “use of these drugs in older patients carries a higher risk of adverse events due to multiple medical comorbidities and drug–drug interactions in the case of polypharmacy,” the study authors wrote.³ When antidepressants are deemed appropriate, selective serotonin reuptake inhibitors are the first-line medication, and lower starting doses and gradual titration are recommended. Other important elements of treatment include lifestyle changes, control of comorbid conditions, and social support.

Currently, Dr Aprahamian and colleagues are “conducting a systematic review and meta-analyses involving researchers from the United Kingdom, the Netherlands, and Brazil to better understand the clinical and diagnostic profile of subthreshold depression,” he said. “This research will help us to address important questions that will inform future cohort studies and clinical trials.”

To further discuss subthreshold depression and relevant diagnostic and treatment implications, Psychiatry Advisor interviewed Mary F. Wyman, PhD, a clinical psychologist and clinical adjunct associate professor at the the University of Wisconsin School of Medicine and Public Health and an advanced fellow in geriatrics at the Willliam S. Middleton Memorial Veterans Hospital in Madison, Wisconsin.

Psychiatry Advisor: What are believed to be reasons for the high rates of subthreshold depression among older adults?

Dr Wyman: For a long time, society and healthcare providers believed that feeling blue or down was a normal part of getting old and that psychological interventions for mental health symptoms were not effective in older people. We have Sigmund Freud to thank for that, in part. So, it was very interesting when large research studies showed that rates of diagnosed depression decrease in later life.

Relevant to subthreshold depression, however, other studies showed that rates of significant depressive symptoms that do not meet diagnostic criteria appear to increase with age. These studies provided support for the category of subthreshold depression, now firmly established as being common among older adults.

Why might subthreshold depression be more common among older adults compared to younger adults, and yet rates of diagnosed depression seem to decrease with age? There are several possible explanations. First, our measurement tools may not work the same with younger adults as with older adults. For example, there is some evidence that depression can present differently among older adults, who may report fewer emotional symptoms, such as low mood, and more physical symptoms.

Since diagnosis using the DSM requires either depressed mood or loss of pleasure along with other symptoms, it may be that young depression fits into current diagnostic criteria and old depression not as much. We do know that older adults are not well represented in mental health research, which informed the development of these criteria, so it could be that the symptoms are present but are not captured in a diagnosis due to the instrument used. It may be that people who survive into old age are generally more resilient or adaptable, and thus less likely to experience severe depression that meets diagnostic criteria. Still, they experience less severe depression.

Finally, we know that subthreshold depression is linked to problems that can be common in later life: medical illness, disability, social network loss, and retirement or other changes that can lead to a lack of purpose in life. These very real challenges might also contribute to high rates of subthreshold depression among older adults.

Psychiatry Advisor: What are some of the screening and diagnostic challenges pertaining to subthreshold depression in older adults?

Dr Wyman: As mentioned above, assessment tools may not be capturing the range of depressive experience that older adults face. In the past, geriatric depression questionnaires were developed because there was concern that physical symptoms unrelated to depression, such as fatigue, poor concentration, low appetite, and sleep problems were leading to inflated scores and thus overestimations of depression among older adults. This can certainly be true. However, there is equal concern that depressive symptoms may be underestimated.

Stigma about mental health conditions can cause older adults and their families to choose to suffer with subthreshold depressive symptoms rather than seek assessment and intervention. Ageism can manifest in family members or healthcare staff buying into inaccurate stereotypes of late life, such as “all older people are depressed,” and not taking steps to help an older person get screened or evaluated. Our work examining attitudes toward aging among caregivers of older women showed that depression in the care recipient is associated with more negative attitudes toward older adults in the caregiver.⁵

There is also increasing evidence that the syndrome of depression is experienced differently in different cultural groups. Our recent work showed that African American older women, compared to white older women, endorsed similar rates of depressive symptoms, but denied impairment related to their depression, and this resulted in them not meeting diagnostic criteria. This probably relates to how the symptoms are perceived—maybe as more normal for the African American women—and what people consider effective coping.

Relevant to subthreshold depression specifically, our findings suggest that it is more severe among African American older women compared to whites and may require tailored treatment.⁶ We need more research in this area, as there is very little information about subthreshold depression among nonwhite older adults. Additionally, there is probably a general problem of subthreshold depression not being recognized as important to treat, or at least to monitor closely through watchful waiting. However, our own [unpublished] work in older women living in the community confirms that subthreshold depression is associated with levels of medical illness and disability at similar levels to diagnosed depression, showing that subthreshold symptoms are not just “a touch of the blues,” but cause considerable suffering among older adults. Meeks, et al wrote a helpful review on the topic.⁷

Psychiatry Advisor: How should clinicians approach screening, diagnosis, and treatment of these patients?

Dr Wyman: Best practice recommendations are that older adults [be] screened regularly for depression, because we know it is so common. Times of loss, illness, or significant changes are also good points to complete a brief screen. I suggest using a validated screening tool such as the PHQ-9 for most older adults, and the GDS-30 for older adults with frailty or impairments, including mild dementia. Both questionnaires have published cut-points for subthreshold symptoms. Take the time to use these cut-points to get a more nuanced sense of the severity of the symptoms, instead of a dichotomous present/absent approach to depression screening.

It is important to always follow-up on a positive screener with a discussion with the patient about the items they endorsed and talk about any symptoms they are experiencing in their own words. Asking about thoughts of self-harm or a passive wish to die is always appropriate when depression or anxiety is elevated.

In primary care, a depression care management approach that may include watchful waiting, medications, or psychotherapy and telephone-based follow-up with the patient to monitor symptoms is considered best practice. For some older adults with subthreshold depression, watchful waiting with monitoring is appropriate. In our [unpublished] work, we found that about a third of older women with subthreshold depression improved over the course of 6 months, even without treatment, consistent with published work from others.

Brief psychotherapeutic approaches that can be helpful include problem-solving therapy, cognitive-behavioral therapy, and behavioral activation. There are effective psychotherapies developed for older adults with dementia and depression, and these patients should also be offered intervention. There are too few psychotherapists trained for work with older adults; however, treatment is effective, and it is critical that clinicians learn about available resources for their older patients with subthreshold depression.

Psychiatry Advisor: What are the remaining needs in this area in terms of clinician education?

Dr Wyman: Provider education is really critical, as very few providers of all disciplines get enough training in geriatric mental health in their professional programs. Continuing education and on-the-job consultation are extremely important. There are various efforts underway right now to train providers in improved older adult depression assessment and treatment, but it is simply not enough. We have a geriatric workforce crisis that is especially critical in mental health, according to the 2012 report from the Institute of Medicine.⁸

References

1. Depression is not a normal part of growing older. Centers for Disease Control and Prevention website. Updated January 31, 2017. Accessed on February 3, 2020.
2. Kok RM, Reynolds CF 3rd. Management of depression in older adults: a review. JAMA. 2017;317(20):2114-2122.
3. Biella MM, Borges MK, Strauss J, Mauer S, Martinelli JE, Aprahamian I. Subthreshold depression needs a prime time in old age psychiatry? A narrative review of current evidence. Neuropsychiatr Dis Treat. 2019;15:2763-2772.
4. Gilbody S, Lewis H, Adamson J, et al. Effect of collaborative care vs usual care on depressive symptoms in older adults with subthreshold depression: the CASPER randomized clinical trial. JAMA. 2017;317(7):728-737.
5. Wyman M, Shiovitz-Ezra S, Parag O. Ageism in informal care network members of older women. Int Psychogeriatr. 2019;31(10):1463-1472.
6. Wyman MF, Jonaitis EM, Ward EC, Zuelsdorff M, Gleason CE. Depressive role impairment and subthreshold depression in older black and white women: race differences in the clinical significance criterion. Int Psychogeriatr. 2019;1-13.
7. Meeks T, Vahia I, Lavretsky H, Kulkarni G, Jeste D. A tune in “A minor” can “B major”: a review of epidemiology, illness course, and public health implications of subthreshold depression in older adults. J Affect Disord. 2011;129(1-3):126-142.
8. Eden J, Maslow K, Le M, Blazer D, eds. The Mental Health and Substance Use Workforce for Older Adults: In Whose Hands? Washington, DC: National Academies Press (US); 2012.