Comorbid anxiety and depression: illumination of a controversy

Depression and anxiety frequently coexist in the same individual, either concurrently or at different times, and numerous studies show that the presence of an anxiety disorder is the single strongest risk factor for development of depression. When the two coexist simultaneously, either as diagnosed disorders or subsyndromal states, they may be viewed as mixed anxiety-depression or as comorbid syndromes, i.e. separate disorders occurring concurrently. Controversy continues over the nature of the relationship between depression and anxiety, some believing they are distinct, separate entities while others - now the majority - view them as overlapping syndromes that present at different points on a phenomenological and/or chronological continuum, and share a common neurobiology, the degree of overlap depending on whether each is described at the level of symptoms, syndrome or diagnosis. Community data likely underestimate true prevalence, since affected individuals frequently present in primary care with somatic, rather than psychological, complaints. Irrespective of the nature of the relationship, patients with both disorders experience significant vocational and interpersonal impairment, and more frequent recurrence, with greater likelihood of suicide, than individuals with single disorders. Various classes of antidepressant drugs offer symptom relief for these patients, the most selective of th SSRIs holding the greatest promise for sustained clinical improvement. Yet, the crucial parameter of successful pharmacotherapy seems to be the length of treatment, ensuring enhancement of the compromised neuroprotective and neuroplastic mechanisms. Further clarification of the relationship is a prerequisite for offering effective treatment to the many patients who experience lifetime depression and anxiety.