Table 2. MPFC Metabolite Levels and Tissue Composition.

	OCD (n=24)	Healthy control (n=22)	95% CI for difference in means
MRS metabolite	Mean (SD)	Mean (SD)
Glx/Wa	1.58 (0.29) × 10−3	1.57 (0.29) × 10−3	−0.17 × 10−3, 0.17 × 10−3
GABA/Wa	2.16 (0.46) × 10−3	2.43 (0.45) × 10−3	0.01 × 10−3, 0.55 × 10−3
Tissue composition	Mean percent (SD)	Mean percent (SD)
Cerebral spinal fluid	10.58 (3.22)	10.32 (3.06)	−2.13, 1.61
Gray matter	53.23 (3.04)	53.72 (2.90)	−1.27, 2.26
White matter	36.19 (3.93)	35.95 (3.60)	−2.48, 2.01

Abbreviations: CI, confidence interval; GABA, γ-aminobutyric acid; Glx, glutamate plus glutamine; MPFC, medial prefrontal cortex (voxel includes the pregenual anterior cingulate cortex); OCD, obsessive–compulsive disorder; W, water.

^aInstitutional units.