How chronic are depressive and anxiety disorders? 9-year general population study using narrow and broad course outcomes.

BACKGROUND

Existing studies on disease course usually apply relatively short follow-up periods and narrow definitions of disease course resulting in too optimistic views on disease prognosis. This study explores the relevance of using a longer and broader (cross-disorder) perspective.

METHODS

Respondents with a 12-month disorder at baseline and available at 3-, 6- and 9-year follow-up were selected (major depressive disorder, MDD: n = 208; anxiety disorder: n = 220) from a general population study (N = 6646). DSM-IV disorders were assessed with the Composite International Diagnostic Interview. Disease course was described using a short and narrow perspective (i.e., 3-year follow-up, and considering presence of the index disorder only) and a long and broad perspective (9-year follow-up, and considering presence of any mood, anxiety or substance use disorder as outcome).

RESULTS

The recovery rates of both MDD and anxiety disorder reduced by half when the perspective switched from short and narrow (MDD: 74.0 %; anxiety disorder: 79.5 %) to long and broad (35.6 % and 40.0 % respectively). At 9-year follow-up, the rates of a persistent disorder (a disorder at each follow-up assessment) tripled when the perspective switched from narrow to broad (MDD: from 4.8 % to 13.9 %; anxiety disorder: from 4.5 % to 15.5 %).

LIMITATIONS

The findings are not generalizable to the most severe depressed and anxious patients.

CONCLUSIONS

Most people with MDD or anxiety disorder in the general population have a rather favourable prognosis when a narrow perspective is applied, but an unfavourable prognosis when a long-term and broad perspective is applied. Consequently, MDD and anxiety disorder should not merely be perceived as episodic disorders, and require longer-term disease monitoring and management.