White matter changes in depression and Alzheimer's disease: A review of magnetic resonance imaging studies

This article reviews magnetic resonance imaging (MRI) studies of white matter lesions in depression and Alzheimer's disease. Although conflicting reports exist, many studies show that white matter lesions are more prevalent in both conditions, with depression associated with deep white matter lesions (DWML) and Alzheimer's disease with periventricular lesions (PVL). In normal ageing and depression there is some evidence that such lesions may be associated with neuropsychological dysfunction, though the relationship is less clear for Alzheimer's disease. One difficulty in drawing firm conclusions from work so far is that confounding variables, such as cerebrovascular risk factors, have now always been taken into account. Most studies have been cross-sectional so there is little information regarding the progression, prognostic significance and pathogenesis of such lesions. These issues merit examination in longitudinal studies combining serial MRI with clinical assessments of subjects who have been fully assessed for vascular risk factors.