The purpose of this paper was to document nationally representative age-specific prevalence rates of DSM-IV mood, anxiety, and comorbid mood-anxiety disorder for adults 55 years and older. There are three key findings in the present study: 1) Declining prevalence with age; 2) Rates of anxiety disorders as high as mood disorders; and 3) The common co-occurrence of these disorders. Rates were generally higher for women in each age group, but did not vary by race or ethnicity.
The first and general finding from our study was the overall trend found for adults of increasing age – a general decline in the 12-month prevalence of mood, anxiety, and comorbid disorder. Statistically, prevalence rates with increasing age were more prominent for 12-month rates among women compared to men (P
< .05). Earlier studies of both clinical and community-based studies suggest such a pattern of decline with age.6,10,34
The ECA found a consistent trend of lower DSM mental disorders in late life when grouping age categories together. Work by Gum et al.20
found a similar trend in the NCS-R with lower rates in older adults (≥ 65 years) vs younger adults (aged 18-64 years). Recent international research by Kohn and colleagues found the same decreasing pattern with age in a sample of adults from Latin America.35
Further, studies have found women to have higher prevalence rates of symptoms of depression, anxiety, and co-existing depression-anxiety than men, while racial differences are less consistent.16-18
Our study found no statistically significant difference across race/ethnicity; however, small cell counts for minority groups equated to lower power to detect a difference.
The second key finding was that rates of anxiety disorders were as high or even higher (with pooled rates higher; overall 12-month = 12%) than mood disorders (overall 12-month = 5%). The age-specific rates of anxiety were higher than mood disorders in each age group, with 12-month rates 17% for those 55 to 64 years old (vs 8% for mood) and 8% for those 85 and older (vs 2% for mood). Similarly, anxiety disorders were the most prevalent disorders among those aged 65 years and older in the ECA with phobic disorder the most prevalent individual disorder.10
Interestingly, we found high prevalence of specific and social phobias, disorders not often investigated and often under appreciated. Of note, unlike our study, the Longitudinal Aging Study Amsterdam (LASA) determined high rates of generalized anxiety disorder (7.3% vs. 2.0% in our study).36
This discrepancy between reported prevalence rates highlights largely methodological differences (e.g., sampling procedures and attrition rates, definition and operationalization of anxiety) and potential cultural differences between population-based studies. Most studies of anxiety disorders among U.S. older adults have been examined relative to their occurrence in patients with depression. Research by Lenze et al.37
found a high rate of at least one current (23%) anxiety disorder in depressed older adults (60 and older) from primary care and psychiatric settings. Work from our group investigating anxiety symptoms in a cohort of community-dwelling older adults (aged 70-79 years) found that 19% of participants reported current anxiety symptoms, where women (20%) had higher rates than men (12%) (P
Our present findings suggest similar results with diagnostic anxiety disorders, which are prominent and pervasive in older adults even into the oldest years.
The third finding was the high rate of co-existing mood and anxiety disorders in NCS-R respondents (overall 12-month = 3%). Geriatric psychiatry research is struggling to understand the comorbid depression-anxiety outcomes and treatment needs. Thus far, the impact of comorbid depression-anxiety is greater than initially estimated. Most U.S. studies have been clinically-based and, as mentioned above, found high prevalence rates of comorbid anxiety in patients with depression.37-39
In contrast, the NCS-R's advantage is that it allows the examination of a nationally representative group—highlighting the impact of comorbid and individual mood and anxiety disorders in the population. Our results showed that the co-occurrence of mood and anxiety disorders in the community was high, common and significant across age strata 55 years and older, investigating overall trends as well as by gender and race/ethnicity.
Investigation of the oldest age cohort (85 years and older), which maintained prominent prevalence rates, warrants comment. Because individuals 85 years and older are not always captured in geriatric psychiatric research, the present examination suggests the need for more research in this group and confronting potential challenges specific to the study of this group. For example, the oldest old are less available for study except in institutional settings and experience heterogeneity of comorbid diseases—creating difficult study of pure disorders in the population.40
Epidemiological evidence for age-specific trends of depression in older adults often measured with the CES-D scale41
or Geriatric Depression Scale (GDS)42
have shown an increase in symptomatology in the oldest cohort,1,9,10,40,43
while in most clinical studies6,10
rates of diagnosed depression consistently decline in older age groups. Thus, understanding diagnostic patterns in the oldest old is complex and requires more investigation than the present study provides.
In contrast, given the strong effect of cognitive and physical health as predictors and outcomes of mental health disorders,1-5
the finding of a general decline in mood, anxiety, and comorbid mood-anxiety disorders with age is counter-intuitive. Three possible explanations for this general decline with age include: 1) Cohort effect (i.e., as the young-old age they will maintain higher levels of mental disorders); 2) Healthy survivor bias or differential mortality, institutionalization (i.e., those institutionalized were not sampled); and 3) Epidemiological methods and diagnostic issues in assessing older adults for psychiatric disorders (e.g., difficulty remembering symptoms, stigma related to the reporting of mental health disorders, somatic symptoms reported but determined to be related to chronic conditions instead of mental health disorders).
The strengths of this study include a nationally representative probability sample, current DSM diagnostic assessment, and precise age-stratification to define trends for young-old, mid-old, old-old, and oldest old cohorts. This study helps to describe the prevalence of mood, anxiety, and comorbid mood-anxiety disorder in a nationally representative sample of older U.S. adults. It highlights those disorders with the greatest potential for intervention and prevention, research and services—translating back into science those diseases with the greatest potential impact on the older public's health.
The implications of the study findings include the public health relevance of anxiety disorders in older adults and the need for more research focused on the oldest old age group, females, and minority groups. Given the high prevalence of anxiety disorders in the community, the lack of attention in research and program policy statements to anxiety disorders in older adults is disturbing.44,45
The literature has shown that comorbid anxiety in depressed elderly patients leads to poorer treatment outcomes than depression alone.38
Thus, the high prevalence of comorbid mood-anxiety disorders found in our study suggests the modifying influence of anxiety on antidepressant treatment outcomes is a serious concern.
The oldest old are the fastest growing age group in the United States.40
The oldest old are often underrepresented so estimates from community samples have been difficult to obtain. Because mental disorders are associated with declining physical health that occurs with frequency in older age,1-5
the assessment of psychiatric disorders is an important indicator of health and increased risk of mortality in this older population.
In addition, these results expand beyond the field of geriatric psychiatry; highlighting the importance of diagnosis, treatment, and management of psychiatric symptoms and disorders in younger years. Given the chronicity of these disorders, preventing their occurrence in later life implies that clinicians and researchers outside geriatrics need to be more vigilant about diagnosis and treatment in early years. These disorders are common in younger adults and most have early age-of-onset, but often are not diagnosed or under-diagnosed and under-treated.21,27
There are three main limitations of this study. First, the NCS-R underrepresents homeless, institutionalized, and non-English speaking older adults. Second, there may be issues of stigma, whereby older adults with mental illness might be less inclined to participate in a mental health survey. Third, even though the WMH-CIDI was shown to have good concordance with the SCID,21
it is still a lay-administered interview rather than a clinically-administered assessment, especially in the context of medical illness, disability, and cognitive decline. Thus, given the above limitations, the estimates herein are probably conservative.
Additional limitations include details associated with surveying older populations that were not available in the NCS-R. These include assessment of the response rate in those aged 55 years and older and demonstration of acceptable reliability of the NCS-R instruments for older adults. Further, the NCS-R was limited in its assessment of mood disorders, as we were unable to determine prevalence rates of some disorders that would be considered common in older adults, e.g., depression NOS, dementia with depression, mood disorders secondary to medical disorders, adjustment disorders with depression, and bereavement. Because depression in older adults may present differently (more apathy, social withdrawal, irritability), the criteria for a major depression diagnosis may not be met, although the other symptoms may be severe, suggesting an underestimation of the prevalence rate in NCS-R older adults. This underestimation is probably large considering the potential for reporting bias in older adults due to difficulty recalling symptoms or difficulty associating symptoms with psychological distress.
The study of nationally representative samples provides evidence for research and policy planning that helps to define community-based priorities for future psychiatric research. The findings of this study emphasize the importance of individual and co-existing mood and anxiety disorders when studying older adults, even the oldest cohorts. Further study of risk factors, course, and severity is needed in order to target intervention, prevention, and health care needs. Given the rapid aging of the U.S. population, the potential public health burden of late-life mental health disorders will likely grow as well, suggesting the importance of continued epidemiologic monitoring of the mental health status of the young-old, mid-old, old-old, and oldest old cohorts.