White matter hyperintensities, suicide risk and late-onset affective disorders: an overview of the current literature

White matter hyperintensities (WMHs) refer to areas of hyperintense signal on T2- or proton density-weighted brain magnetic resonance imaging. Although WMHs are a common finding in patients with bipolar disorder (BD), particularly with a later disease onset, some studies report a higher frequency of WMHs only in unipolar affective disorders. We reviewed the literature examining examining both the severity and presence of WMHs in late life and particularly in individuals with late-onset BD (LOBD). Studies investigating white matter lesions in LOBD were systematically retrieved and the reference lists of these studies were scanned for additional relevant studies of neuroimaging in LOBD. The majority of neuroimaging studies reported an association between older age and LOBD and the presence of WMHs in LOBD. Also, we found in a small sample of patients preliminary evidence of a significant relationship between older age with late-onset BD and WMHs having a higher prevalence of cardiovascular and cerebrovascular risk factors. In conclusion over 60 years older individuals with LOBD and WMHs might have a type of illness characterized by more neuropathological changes and biologically different compared to non LOBD. This is consistent with the hypothesis of vascular mania. WMHs could be a reliable biological risk marker for late onset mood disorders.