Hemispheric Asymmetry in Depression: An Overview

Indian Journal Social Science Researches
Vol. 6, No. 1, March, 2009, pp. 16-28
ISSN 0974-9837

Hemispheric Asymmetry in Depression: An Overview
Rakesh Pandey* and Garima Gupta**
The present paper attempts to review empirical evidences dealing with the nature of hemispheric asymmetry in depression. The early empirical evidences obtained from the study of unilateral focal brain damaged patients suggested that left hemisphere damage is associated with depression whereas the right hemisphere damage with manic like features. These observations extended the right hemispheric hypothesis of depression. However, the review suggests that this hypothesis is not unanimously agreed upon, researchers have extended alternative interpretations, and hypotheses (e.g., left hemisphere hypoactivation). Furthermore, the clinical studies suffered from several methodological problems that limit the generalization of the conclusion for intact brain individuals suffering from depression. Taking the limitations of the clinical studies into account, hemispheric asymmetry studies conducted on intact brain depressive patients were also reviewed. However, these studies also yielded inconsistent findings.
Most of the studies reported either a left hemisphere hypoactivation or a right hemisphere hyperactivation in depression and a few observed right hemisphere hypoactivation. However, subsequent studies suggested that depression might be characterized by a reciprocal hypoactivation of the left hemisphere and hyperactivation of the right. Overall, a critical look on the available empirical evidences reveals the possibility that left hemisphere hypoactivation and right hemisphere hyperactivation hypotheses might be complementary in nature and the former might be a trait whereas the latter being a state dependent phenomenon. However, still there are a number of methodological and theoretical issues that need to be addressed in future research before accepting and generalizing

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