Perceptual Asymmetry in Depression: Role of Co-morbid Anxiety

Anxiety disorder is the most prevalent psychiatric co-morbidity in depression [1-3] and many researchers argue that it is present in lesser or greater degree in almost all cases of depression [4,5]. The clinical picture and severity of symptoms become worse in patients having incidence of psychiatric co-morbidity in depression and these observations pose a methodological difficulty in uncovering the underlying hemispheric base of depression inasmuch as both anxiety and depression are associated with negative affect and both conditions generally co-occur in a patient. Thus, any study of hemispheric asymmetry in depression is fraught with methodological difficulty of differentiating how far the observed hemispheric changes in depression is due to the clinical syndrome of depression and how far it is associated with symptoms of anxiety. Delineating the difference in hemispheric functioning associated with depression and co-morbid anxiety disorder becomes further complicated by the fact that both are associated with higher prevalence of negative affect that has often been associated with a pattern of hemispheric asymmetry similar to that observed for anxiety and depression. Considering anxiety while investigating brain function in depression has been repeatedly emphasized [6-11] inasmuch as both depression and anxiety may be associated with different pattern of hemispheric functioning [9] and the possibility that co-morbid presence of anxiety disorders can alter the observed pattern of hemispheric asymmetry in depression has been empirically demonstrated in various studies [12-14].