Oligodendrocytes have been studied in depressive disorders (Edgar et al. 2012) (see Table III). There is white matter attenuation in MDD, especially in geriatric samples (Taylor et al. 2003, 2004), and this has been confirmed in several postmortem MDD studies (Regenold et al. 2007; Hayashi et al. 2011). Oligodendrocyte density is also decreased in the postmortem MDD brain (−19%) in PFC layer VI and surrounding white matter (Brodmann’s area 9) compared to non-psychiatric controls (Uranova et al. 2004). Decreased oligodendrocyte density has also been observed in sublayers IIIa, IΠb, and IΠc of Brodmann’s area 9 (Vostrikov et al. 2007) and in the amygdala of individuals with MDD but not BD (Hamidi et al. 2004). Other white matter corticolimbic circuitry abnormalities have been observed in BD (Mahon et al. 2010).
