Decreased Prefrontal Myo-Inositol in Major Depressive Disorder

Background Postmortem studies have shown robust prefrontal cortex glial losses and more subtle neuronal changes in major depressive disorder (MDD). Earlier proton magnetic resonance spectroscopy (1H-MRS) studies of the glial marker myo-inositol in MDD were subject to potential confounds. The primary hypothesis of this study was that MDD patients would show reduced prefrontal/anterior cingulate cortex levels of myo-inositol. Methods Thirteen nonmedicated moderate–severe MDD patients and 13 matched control subjects were studied (six male, seven female per group). Proton magnetic resonance spectroscopy stimulated echo acquisition mode spectra (3.0 T; echo time = 168 msec; mixing time = 28 msec; repetition time = 3000 msec) were obtained from prefrontal/anterior cingulate cortex. Metabolite data were adjusted for tissue composition. Results Patients with MDD showed significantly lower myo-inositol/creatine ratios (.94 ± .23) than control subjects (1.32 ± .37) [F(1,23) = 6.9; p = .016]. Conclusions These data suggest a reduction of myo-inositol in prefrontal/anterior cingulate cortex in MDD, which could be a consequence of glial loss or altered glial metabolism. Additional in vivo studies of glial markers could add to the understanding of the pathophysiology of MDD.