Comorbidity and risk-patterns of depression, generalised anxiety disorder and mixed anxiety-depression in later life: results from the AMSTEL study

BACKGROUND: Depression and generalised anxiety disorder frequently overlap. The question remains unresolved whether these are specific disorders, or that they represent different dimensions of a single disorder. Although both are highly prevalent disorders in this age group, studies on this issue in the elderly are scarce. Research is needed that investigates patterns of comorbidity and possibly different risk profiles for pure depression, pure generalised anxiety and mixed anxiety-depression in older people. METHODS: GMS-AGECAT diagnoses were obtained from 4051 community living older persons. Comorbidity was studied along a severity gradient for men and women separately. Multivariate analysis of risk factors included demographic variables, environmental vulnerability, longstanding vulnerability, physical/functional stresses and gender. RESULTS: The prevalence of pure depression was 12.2%, pure generalised anxiety 2.9%, mixed anxiety-depression 1.8%. Comorbidity increased with higher severity levels of both depression and generalised anxiety. Comorbidity was twice as likely in women than in men. Different risk profiles for diagnostic categories were not demonstrated for concurrent risk factors. Longstanding vulnerability was associated significantly stronger with mixed anxiety-depression than with pure anxiety and pure depression. Mixed anxiety-depression was overrepresented in women. CONCLUSIONS: Both lines of investigation suggest that, in the elderly, a dimensional classification is more appropriate than a categorical classification of depression and generalised anxiety. Mixed anxiety-depression is a more severe form of psychopathology that is almost specific to women in this age group.