Depression is reported to be associated with increased mortality, but underlying mechanisms are uncertain. Associations between anxiety and mortality are also uncertain. In a large population study, we investigated associations between anxiety, depression and mortality over a 3-6 year period. We utilized a unique link between a large regional community survey and a comprehensive national mortality database.

Baseline information on mental and physical health was collected in a population-based health study (n=61,349) (the HUNT-2 study) of adults aged 20 years and over. Anxiety and depressive symptoms were ascertained using the Hospital Anxiety and Depression Scale (HADS). Records were linked with the Norwegian national mortality database.

Case-level depression was a risk-factor for mortality, but case-level anxiety was not (having adjusted for confounding factors). The association between anxiety symptoms and mortality was U-shaped, and anxiety comorbid with depression was associated with lower mortality compared to depression alone. Associations between depression and mortality were partly but not entirely explained by somatic symptoms and conditions, and also physical impairment, but not by smoking, obesity, cholesterol level or blood pressure.

Depression predicted general mortality after adjustment for multiple potential confounding factors. Associations between anxiety symptoms and mortality were U-shaped. Lower mortality was found in comorbid anxiety and depression than in depression alone.