Changes in corpus callosum area and thickness have been reported in bipolar disorder. Imaging and limited neuropathological data suggest possible abnormalities in myelination and/or glial function.

To compare corpus callosum area, thickness and magnetic resonance imaging (MRI) T 1 signal intensity in patients with bipolar disorder and healthy controls.

A total of 48 patients with euthymic bipolar disorder and 46 healthy controls underwent MRI analysis of callosal midsagittal area, callosal thickness and T 1 signal intensity.

The bipolar group had smaller overall and subregional callosal areas and correspondingly reduced callosal width than the control group. Age correlated negatively with callosal area in the control group but not in the bipolar group. Signal intensity was higher in women than in men in both groups. Signal intensity was reduced in women, but not in men, in the bipolar group.

Observed differences probably relate to diagnosis rather than mood state and bipolar disorder appears to result in morphometric change that overrides changes seen in normal ageing. Intensity changes are consistent with possible altered myelination or glial function. A gender-dependent factor appears to operate and to interact with diagnosis.

Cerebrovascular changes and glucocorticoid mediated hippocampal atrophy are considered relevant for depression-related cognitive deficits, forming putative treatment targets.

This study examined the relative contribution of cortisol levels, brain atrophy and white matter hyperintensities to the persistence of cognitive deficits in older adults with depression.

Thirty-five people aged ⩾60 years with DSM–IV major depression and twenty-nine healthy comparison controls underwent magnetic resonance imaging (MRI) and were underwent magnetic resonance imaging (MRI) and were followed up for 18 months. We analysed the relationship between baseline salivary cortisol levels, whole brain, frontal lobe and hippocampal volumes, severity of white matter hyperintensities and follow-up cognitive function in both groups by testing the interaction between the groups and these biological measures on tests of memory, executive functions and processing speed in linear regression models.

Group differences in memory and executive function follow-up scores were associated with ratings of white matter hyperintensities, especially of the deep white matter and periventricular regions. Compared with healthy controls, participants with depression scoring within the third tertile of white matter hyperintensities dropped two and three standard deviations in executive function and memory scores respectively. No biological measure related to group differences in processing speed, and there were no significant interactions between group and cortisol levels, or volumetric MRI measures.

White matter hyperintensities, rather than cortisol levels or brain atrophy, are associated with continuing cognitive impairments in older adults with depression. The findings suggest that cerebrovascular disease rather than glucocorticoid-mediated brain damage are responsible for the persistence of cognitive deficits associated with depression in older age.

Abnormal diffusion parameters are reported in specific brain regions and white matter tracts in bipolar disorder.

To investigate whether these abnormalities are generalised, and thus evident in large regions of white matter.

Diffusion parameters were measured at several regions in the corpus callosum and in deep/periventricular white matter in 28 currently euthymic patients with bipolar disorder and controls. White matter hyperintensity loads were assessed.

Comparing the whole data-sets using the sign test, in the group with bipolar disorder, mean diffusivity was greater at all 15 sites (P<0.001) and fractional anisotropy was reduced at 13 (P<0.01). The effect of diagnosis was significant for callosal mean diffusivity and fractional anisotropy and for deep/periventricular mean diffusivity (MANCOVA). Comparing individual regions (Mann–Whitney U-test), prefrontal and periventricular mean diffusivity were significantly increased; callosal and occipital fractional anisotropy were significantly reduced. Former substance use and lithium were possible confounding factors. Periventricular white matter hyperintensities were associated with significantly increased periventricular mean diffusivity in individuals with bipolar disorder.

Generalised white matter microstructural abnormalities may exist in bipolar disorder, possibly exacerbated by past substance use and ameliorated by lithium.

Evidence for structural hippocampal change in depression is limited despite reports of neuronal damage due to hypercortisolaemia and vascular pathology.

To compare hippocampal and white matter structural change in demographically matched controls and participants with early-onset and late-onset depression.

High-resolution volumetric magnetic resonance imaging (MRI) and rating of MRI hyperintensities.

A total of 51 people with depression and 39 control participants were included. Participants with late-onset depression had bilateral hippocampal atrophy compared with those with early-onset depression and controls. Hippocampal volumes did not differ between control participants and those with early-onset depression. Age of depression onset correlated (negatively) with hippocampal volume but lifetime duration of depression did not. Hyperintensity ratings did not differ between groups.

Results suggest that acquired biological factors are of greater importance in late-than in early-onset illness and that pathological processes other than exposure to hypercortisolaemia of depression underlie hippocampal atrophy in depression of late life.