White matter hyperintensities in bipolar and unipolar patients with relatively mild-to-moderate illness severity

Background: Increased rates of white matter hyperintense lesions have been reported in mood disorder patients. However, the potential effects of age and illness severity on reported findings are not fully established. We examined the rates of hyperintense lesions in adult, non-elderly bipolar and unipolar patients, with a relatively mild-to-moderate illness severity, and in matched healthy controls. Method: We examined brain MRI images in 24 bipolar (19–56 years, mean±S.D.=34.2±9.9 years) and 17 unipolar patients (24–59 years, 42.8±9.2 years), and 38 healthy controls (21–59 years, 36.8±9.7 years). T2-weighted and proton-density axial MRI images were obtained at 1.5 Tesla. The lesions were rated by two independent raters, using a semi-quantitative rating scale. Results: There were no significant differences in the frequency of hyperintensities between bipolar or unipolar patients and healthy controls. Age was related to the presence of subcortical gray matter hyperintensities for the whole sample. Among the unipolar patients, length of illness and presence of mood disorder in a first-degree relative were related to deep and periventricular white matter lesions, respectively. Limitations: The methodology utilized for measurement of the white matter hyperintensities was semi-quantitative. Conclusions: Increased rates of white matter hyperintensities do not appear to be present in a group of relatively young mood disorder patients, with relatively mild to moderate illness severity. These brain lesions may be more directly related to late-life and more severe cases of these illnesses.