Depression, subthreshold depression and comorbid anxiety symptoms in older Europeans: Results from the EURODEP concerted action

Abstract

Background

In the epidemiology of late life depression, few insights are available on the co-occurrence of subthreshold depression and comorbid symptoms of anxiety. The current study aims to describe prevalence patterns of comorbid anxiety symptoms across different levels of depression in old age, and to describe the burden of depressive symptoms and functional disability across patterns of comorbidity.

Methods

Respondents were older adults in the community, age 65–104 (N=14,200), from seven European countries, with in total nine study centres, collaborating in the EURODEP concerted action. Depression and anxiety were assessed using the Geriatric Mental State examination (GMS-AGECAT package), providing subthreshold level and case-level diagnoses. Presence of anxiety symptoms was defined as at least three distinct symptoms of anxiety. Number of depressive symptoms was assessed with the EURO-D scale.

Results

The prevalence of anxiety symptoms amounts to 32% for respondents without depression, 67% for those with subthreshold depression, and 87% for those with case-level depression. The number of depressive symptoms is similar for those with subthreshold-level depression with comorbid anxiety, compared to case-level depression without symptoms of anxiety. In turn, at case level, comorbid symptoms of anxiety are associated with higher levels of depressive symptoms and more functional disability.

Limitations

GMS-AGECAT is insufficiently equipped with diagnostic procedures to identify specific types of anxiety disorders.

Conclusions

Anxiety symptoms in late life depression are highly prevalent, and are likely to contribute to the burden of symptoms of the depression, even at subthreshold level.

Introduction

Although categorised as different nosological entities, depression and anxiety frequently co-occur. Jacob et al. (1998) even conclude that mixed conditions are more common than pure depression or pure anxiety. The pattern has also been reported to pertain to older adults (Byers et al., 2010): in the NCS-R study in the US, over half of the older adults with a depressive disorder suffered from comorbid anxiety. The 10/66 study showed similar results, comparing a range of participating centres with samples aged 65 years and older from different countries in Asia and South and Central America (Prina et al., 2011). In these studies, anxiety disorders were diagnosed according to DSM-IV criteria (6 months for GAD) or to GMS-AGECAT case definition with levels of severity that warrant professional intervention. In other studies focusing on mixed depression and anxiety, these criteria were relaxed to 1 month recency, yielding higher rates and higher comorbidity levels (Kendler et al., 2007, Kendler and Gardner, 2011).

Prina et al. (2011) showed that having both depression and anxiety was linked to higher disability scores than having depression or anxiety alone. Similarly, comorbid depressive-anxiety disorder was more strongly associated with several physical conditions than were single mental disorders (Scott et al., 2007). Moreover, comorbid anxiety and depression result in a poorer course than non-comorbid depression or anxiety (Fava et al., 2008, Rhebergen et al., 2011), also in later life (Schoevers et al., 2005).

Whereas the epidemiology of depression and comorbid anxiety receive substantial research evidence, few insights are available on the co-occurrence of subthreshold depression and comorbid symptoms of anxiety. Subthreshold depression in later life, however, frequently runs a chronic course or tends to develop into an episode of major depressive disorder (Beekman et al., 2002). Subsequently, the severity of the condition warrants clinical intervention and can be defined as ‘case’. As advocated by Batelaan et al., comorbid subthreshold conditions of depression and anxiety are in need of more research (2012). Therefore, population-based studies can facilitate obtaining further insight into patterns of comorbidity as well as the severity of comorbid, subthreshold depression and symptoms of anxiety.

The current, population based study employs data from the centres participating in the EURODEP concerted action (Copeland, 1999a), and addresses the following research questions:

• What patterns of comorbid, late life anxiety symptoms with different levels of depression do occur? Do levels of comorbidity persist into very old age?

• What is the burden of depressive symptoms and functional disability among older adults with depression across levels of caseness (non-case, subthreshold and diagnostic case) for those without and with comorbid symptoms of anxiety?