Depression and anxiety are two of the most commonly occurring comorbid psychological conditions. Research estimates that nearly 65% of people who have a history of generalized anxiety (GAD) also experience symptoms of major depression (MDD). Additionally, a very high percentage of people with MDD have also experienced episodes of GAD. The two conditions share some symptoms, such as memory and concentration problems and impaired sleep. Both GAD and MDD are also believed to be influenced by genetic factors and childhood experiences. However, the two conditions are also thought to have unique and varied course trajectories and symptoms relative to each such as negative affect (in MDD) and fear and worry (in GAD).
Because of these similar and differing dimensions of GAD and MDD, some experts have begun to theorize that perhaps MDD actually covers the symptoms of GAD. To explore this further, Anna Weinberg of the Department of Psychology at Stony Brook University in New York recently led a study using error-related negativity (ERN) tests to assess the levels of GAD in 26 female participants with GAD, 23 with both MDD and GAD and 36 with no history of either condition. After conducting error response experiments on all of the participants, Weinberg found that the ERN in the individuals with comorbid MDD and GAD was similar to that found in the GAD participants.
This finding suggests that MDD does not enhance the GAD symptoms. In particular, MDD did not produce the same physiological results as GAD. If it did, as some experts theorize, the ERN in the comorbid participants would be higher than the ERN of the participants with GAD alone. The outcome of this study supports evidence that the dimensions and trajectories of GAD and MDD symptoms are not redundant but act in distinct and singular ways. Understanding how these two conditions affect each other and manifest or mask symptoms is an area that warrants further exploration. Weinberg said, “The present results highlight the possible moderating effects of comorbid disorders in GAD and emphasize the need to examine or control for comorbidity in future studies.”
Weinberg, A., Klein, D. N., Hajcak, G. (2012). Increased error-related brain activity distinguishes generalized anxiety disorder with and without comorbid major depressive disorder. Journal of Abnormal Psychology. Advance online publication. doi: 10.1037/a0028270
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