Depression may often precede anxiety

NEW YORK (Reuters Health) - Contrary to the prevailing belief, it is nearly as likely that major depressive disorder will develop into a generalized anxiety disorder, as the reverse pattern, according to a study published in the June issue of the Archives of General Psychiatry. Moreover, the lifetime prevalence of both anxiety and depression has probably been underestimated.

"The close association between generalized anxiety disorder and major depressive disorder prompts questions about how to characterize this association in future diagnostic systems," write Dr. Terrie E. Moffitt, of King's College London, UK, and colleagues. Most information about having both of these conditions at the same time "comes from patient samples and a review of patient records.

Using data from a long-term study, the researchers examined the sequential and cumulative relationship between generalized anxiety disorder and major depressive disorder. Included were 1,037 participants born between 1972 to 1973 in New Zealand, who were followed up to age 32. Diagnoses of anxiety and depression were made at seven time intervals between age 11 age 32.

The researchers report that anxiety began before or at the same time as depression in 37-percent of depression cases. Depression began before or concurrently in 32 percent of anxiety cases.

Forty-eight percent of lifetime depression cases had lifetime anxiety disorder, and 72 percent of lifetime anxiety cases had lifetime depression.

Overall, 12 percent of the subjects had comorbid anxiety disorder and major depressive disorder during adulthood. Of these, 66 percent had recurrent major depressive disorder and 47 percent had recurrent generalized anxiety disorder.

Sixty-four percent of the cohort utilized mental health services and 47 percent took psychiatric medications. The team reports that 8 percent of the patients were hospitalized and 11 percent attempted suicide.

Because of the strong relation between generalized anxiety disorder and major depressive disorder, they could be classified as a single category of distress disorders, Moffitt and colleagues suggest.

They also conclude from their findings that "generalized anxiety disorder-major depressive disorder comorbidity may affect more of the adult population and constitute a greater health burden than previously thought."

Arch Gen Psychiatry 2007;64:651-660.