Muscle tension and physiologic hyperarousal, performance, and state affectivity: assessing the independence of effects in frequent headache and depression.

Anxiety, depression, and frequent headache are closely associated. The comorbidity may be due to selection bias (such as inherent in treatment seeking), shared environmental or genetic factors, or a common underlying process. In this study, comorbidity is considered an alternative explanation for correlates of frequent headache found in earlier work. This study addressed whether EMG, peripheral temperature, performance measures, and measures of affect were independently attributable to depression or headache proneness, after control of trait anxiety. Headache state was evaluated in parallel analysis. Seventy-two participants, comprising four groups, were tested: depressed/headache-prone depressed/headache-resistant, not depressed/headache-prone, and not depressed/headache-resistant. Participants completed a performance task that allowed assessment of ambition and performance accuracy while measures of affect, headache state, EMG, and peripheral temperature were obtained. Headache proneness, independently of depression and trait anxiety, was related to heightened EMG. Depression was related to EMG, ambition, and performance accuracy independently of headache proneness and trait anxiety. Headache state was associated only with negative affect, independently of depression and anxiety. These results suggest that headache states during assessment, as well as comorbid depression and anxiety, are not primarily responsible for the heightened EMG found in headache-prone individuals. Negative affect often reported in the headache prone, however, may be due to concommitant anxiety. Other analyses address a variety of issues surrounding distinctions among these variables raised in previous research.