The differential relationship between trait anxiety, depression, and resting frontal α-asymmetry

Relatively larger resting right frontal cortical brain activation has been labeled as a risk factor for emotion-related disorders. In light of this framework, the present studies' aim was twofold. First, we wanted to determine whether a relationship between symptoms of anxiety and depression and frontal asymmetry does already manifest in a sample of so far healthy individuals showing a large symptom range. This could be expected if frontal asymmetry constitutes a risk factor for depression and anxiety. Second, we aimed to investigate whether symptoms of depression and anxiety are independently related to frontal asymmetry, or whether either anxiety or depression is superior in predicting the relationship with frontal asymmetry. To address these questions, trait-like resting frontal alpha-asymmetry by means of EEG, as well as trait anxiety and depressive symptoms by questionnaire were measured from 43 healthy students (28 female). Results indicate that higher symptom severity of depression and anxiety were both significantly correlated with relatively larger right frontal cortical activation. However, in a regression analysis, frontal asymmetry was predicted by anxiety only. Controlling for depression and mood, anxiety explained 13% of variance, while controlling for mood and anxiety, depression did explain < 1% of variance within frontal asymmetry. In conclusion, although both anxiety and depression add to the relationship, relatively larger right frontal cortical activity might be influenced more strongly by symptoms of anxiety. Moreover, as this effect is present already in healthy individuals, the findings might further support the notion that right frontal cortical asymmetry constitutes a risk factor for anxiety or depression.