Mood state linked to differences in gray matter density in BD patients
MedWire News: Results from a preliminary US study suggest that patients with bipolar disorder (BD) display differences in gray matter density according to mood state.
"The structural neuroimaging literature is rife with studies describing gray matter density abnormalities in patients with bipolar disorder," observe John Brooks and colleagues from the University of California at Los Angeles School of Medicine.
They explain that many structural imaging studies of bipolar disorder have analyzed patients regardless of mood state, reflecting an assumption that cortical structure is impervious to state-related changes.
However, the team adds that "recent evidence, including data from our group, suggests that gray matter density may be associated with mood state."
To investigate further, the researchers studied seven patients (three women), aged an average of 42.4 years, with BD who were in a depressed mood state at baseline, as indicated by a score of greater than 18 on the Hamilton Depression (HAM-D) 21-item scale and a score of less than seven on the Young Mania Rating scale.
Patients were excluded from the study if they had hypertension, neurological illness, metal implants, and a history of skull fracture or head trauma, or had abused substances within the past 6 months.
They were followed longitudinally until they had achieved remission with a HAM-D score of less than seven for at least 2 weeks.
All of the patients underwent brain magnetic resonance imaging scans during the depressed mood state, and again during the remitted (euthymic) state. The mean time in a euthymic state before the second scan was 4.7 weeks.
The researchers found that patients exhibited significantly reduced gray matter density in the superior (Brodmann's Area [BA] 10), medial (BA 4), and inferior frontal gyri (BA 46), the anterior cingulate (BA 32), and the lingual gyrus when depressed compared with when euthymic.
They also displayed significant increases in gray matter density in the subgenual prefrontal cortex (BA 25), the inferior temporal gyrus (BA 20), and the parahippocampal gyrus when depressed compared with when euthymic.
These changes in gray matter density between depression and euthymia were not significantly associated with age, illness duration, number of affective episodes, or change in HAM-D score, the researchers note.
Brooks and team conclude: "Our preliminary data suggest mood state can alter gray matter structure."
They add: "The lack of consensus among prior structural neuroimaging studies of BD could reflect, in part, the varied mood states of the patients.
"It is unclear whether these changes presage functional changes observed in studies of cerebral blood flow and metabolism. What is clear, however, is that the mood state of patients cannot be ignored in neuroimaging studies of bipolar disorder."
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By Mark Cowen