Background: Insight refers to an awareness and attribution of disorders and attitude toward treatment. While neurocognitive studies indicate that lack of insight is associated with frontal lobe dysfunction, little is known about the neurobiochemical profile of insight. We investigated the neurobiochemical characteristics of insight within the frontal lobe using proton magnetic resonance spectroscopy ((1)H MRS) among elderly people with major depressive disorders in remission.
Methods: Seventy-five elderly patients with major depressive disorder in remission underwent assessment of insight using the Mood Disorders Insight Scale (MDIS), including awareness, attribution, and need for treatment. Brain (1)H MRS spectra were acquired from voxels located in the left frontal lobe. Ratios of N-acetylaspartate (NAA), choline, and myo-inositol reference to total creatine (tCr) were calculated. Correlations between these biochemical ratios and insight were examined. Secondary analyses included the association of biochemical ratios with each of the subscales of insight.
Results: Twenty (26.7%) study participants scored full points on the MDIS scale. Total scores of MDIS correlated with NAA/tCr (rho=0.31; p<0.006) in the left frontal lobe. Secondary analyses showed the depressive elders with inadequate attribution to their disease had lower levels of NAA/tCr than those with full insight regarding attribution.
Conclusions: Biochemical changes on (1)H MRS support that the left frontal lobe may involve insight and relate more specifically to disease attribution. Lower levels of NAA/tCr suggest that the neuronal dysfunction in the left frontal lobe is associated with inadequate insight in late-life depression.
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