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.