Table 1. Summary of included studies.

Author	Mean age (year)	N of OCDa	N of male OCDa	N of HCa	N of male NHCa	Diagnostic tool	Duration of illness (year)	Psychiatric comorbidity	Medication	Y-BOCSb			Magnetic field strength (tesla)	Segmentation	MRS sequence	Single- vs multi- voxel	Types of measure	TE (ms)	TR (ms)	NAA	Cre	Cho	mI	Glx	VOI location	VOI size (ml)	Results
										Total	Obsession	Compulsion
Atmaca et al.51	28.1	18	6	18	6	DSM-IV	5.5	No	No	17.2	NA	NA	1.5	Undone	NA	Single	Cre ratio	15.6	2000	○	○	○	×	×	bl.hippocampus	4.7	NAA↓
Bartha et al.50	34.9	13	7	13	7	DSM-IV	NA	No	No	25.9	11.6	14.3	1.5	Undone	NA	Single	Absolute	20	1500	○	○	○	○	○	lt.corpus striatum	4.5	NAA↓
Beédard et al.43	40.54	13	4	12	4	DSM-IV	12.77	No	Medicated	26.5	12.92	13.62	1.5	Undone	PROBE	Single	Cre ratio	102	3100	○	×	○	○	○	rt.OFA	8	NS
																				○	×	○	○	○	lt.OFA	8	NS
																				○	×	○	○	○	rt.MTL	8	NS
																				○	×	○	○	○	lt.MTL	8	NS
																				○	×	○	○	○	rt.thalamus	9	NS
																				○	×	○	○	○	lt.thalamus	9	NS
																				○	×	○	○	○	ACC	9.6	NS
Besiroglu et al.42	32.1	30	12	15	6	DSM-IV	6.35	No	No	24.15	13.1	11.05	1.5	Undone	PRESS	Single	Absolute Cre ratio	135	1500	○	○	○	×	×	rt.ACC	8	NAA↓
																				○	○	○	×	×	rt.AHC	4.096	NAA↓
Ebert et al.34	27	12	8	6	5	DSM-IV	11	No	No	28	NA	NA	2	Undone	PRESS	Single	Cre ratio	30	1500	○	×	○	○	○	ACC	8	NAA↓
																				○	×	○	○	○	rt.striatum	8	NAA↓
																				○	×	○	○	○	rt.PL	8	NS
Fan et al.24	25.62	21	12	19	13	DSM-IV	4.45	No	No	22.52	NA	NA	1.5	Undone	PRESS	Single	Cre ratio	35	1500	○	×	○	○	×	MPFC	8	NAA↓
Jang et al.22	27.77	13	8	13	8	DSM-IV	7.23	Two: depression	No	30.23	15.31	14.92	1.5	Done	PRESS	Multi	Cre ratio	272	2000	○	×	×	×	×	ACC	1.125	NAA↓
																				○	×	×	×	×	FWM	1.125	NAA↓
																				○	×	×	×	×	Prefrontal cortex	1.125	NAA↓
																				○	×	×	×	×	PC	1.125	NS
																				○	×	×	×	×	PWM	1.125	NS
																				○	×	×	×	×	Posterior cingulate	1.125	NS
Kitamura et al.26	22.7	12	3	32	10	DSM-IV	6.3	No	Medicated	20.4	NA	NA	3	Undone	PRESS	Single	Cre ratio	24	6000	○	×	○	×	×	ACC	3	NS
																				○	×	○	×	×	lt.basal ganglia	6.75	NS
																				○	×	○	×	×	lt.thalamus	3.375	NS
																				○	×	○	×	×	lt.FWM	3.375	NS
																				○	×	○	×	×	lt.PWM	3.375	NS
Mirza et al.38	10.31	27	13	18	NA	DSM-IV	2.63	No	No	26.8	NA	NA	1.5	Undone	NA	Single	Absolute	272	2300	○	○	○	×	×	lt.thalamus	0.8	NS
																				○	○	○	×	×	rt.thalamus	0.8	NS
Mohamed et al.28	36.7	10	4	10	4	DSM-IV	23.5	No	Medicated	14.3	NA	NA	1.5	Undone	NA	Single	Cre ratio	280	2650	○	×	○	×	×	lt.thalamus	1.1	NS
																				○	×	○	×	×	rt.thalamus	1.1	NAA↓
																				○	×	○	×	×	lt.basal ganglia	1.1	NS
																				○	×	○	×	×	rt. basal ganglia	1.1	NS
Ohara et al.35	24.5	12	10	12	10	DSM-IV	5.6	No	Medicated	29.5	NA	NA	1.5	Undone	PROBE	Single	Cre ratio	40	1500	○	×	○	×	×	lt.lenticular nucleus	8	NS
																				○	×	○	×	×	rt.lenticular nucleus	8	NS
Rosenberg et al.23	11.39	20	9	14	5	DSM-IV	3.87	Two: anxiety	No	25.8	NA	NA	1.5	Undone	PRESS	Single	Absolute	272	2300	○	○	○	○	○	ACC	3	NS
Rosenberg et al. 37	11.19	11	4	11	4	DSM-IV	2.56	Yes: anxiety	No	26.55	NA	NA	1.5	Undone	PRESS	Single	Absolute	272	2300	○	○	○	×	×	lt.medial thalamus	NA	NS
																				○	○	○	×	×	rt.medial thalamus	NA	NS
																				○	○	○	×	×	lt.lateral thalamus	NA	NS
																				○	○	○	×	×	rt.lateral thalamus	NA	NS
Rosenberg et al.36	11	11	4	11	4	K-SADS-PLc	1.2	Yes: anxiety	No	30.36	15.27	15.09	1.5	Undone	PRESS	Single	Absolute	272	2300	○	○	○	○	○	lt.caudate	0.7	NS
																				○	○	○	○	○	Occipital gray matter	8	NS
Scherk et al.40	NA	17	NA	16	NA	DSM-IV	NA	No	Medicated	NA	NA	NA	1.5	Undone	NA	Single	Cre ratio	30	1500	○	×	○	○	○	DLPFC	3.5	NS
																				○	×	○	○	○	PMFC	3.6	NS
																				○	×	○	○	○	Putamen	3.3	NS
Starck et al.41	32.6	9	6	15	11	DSM-IV	19.4	Yes: depression	Medicated	22.9	11.9	11	1.5	Undone	PRESS	Single	Absolute	30	2000	○	○	○	○	○	rt.caudate nucleus	1.5	NA
																				○	○	○	○	○	Anterior cingulate gyrus	3.6	NA
																				○	○	○	○	○	OC	4	NA
Sumitani et al.27	29.99	20	13	26	10	DSM-IV	NA	NA	Medicated	23.79	NA	NA	1.5	Done	STEAM	Single	Absolute	18	5000	○	○	○	×	×	ACC	4.335	NAA↓
																				○	○	○	×	×	lt.basal ganglia	4.335	NS
																				○	○	○	×	×	lt.FL	4.335	NS
Whiteside et al.39	41.2	15	9	15	9	DSM-IV	23.09	Yes: depression	Medicated	24.13	11.73	12.4	1.5	Undone	PROBE	Single	Cre ratio	35	2000	○	×	○	○	○	lt.head of caudate	4	NS
																				○	×	○	○	○	rt.head of caudate	4	NS
																				○	×	○	○	○	lt.OFWM	4	NS
																				○	×	○	○	○	rt.OFWM	4	NAA↓
Yucel et al.31	34.4	20	10	26	13	DSM-IV	13.4	NA	No/stable	19.55	9.35	10.2	3	Done	PRESS	Single	Absolute	30	3000	○	○	○	○	○	rt.dACC	6.5	NS
																				○	○	○	○	○	rt.rACC	6.5	NS
																				○	○	○	○	○	lt.dACC	6.5	NS
																				○	○	○	○	○	lt.rACC	6.5	NS

Abbreviations: ACC, anterior cingulate cortex; AHC, amygdala hippocampus complex; bl., bilateral; Cre,creatine; dAC, dorsal anterior cingulate; dACC, dorsal anterior cingulate cortex; DLPFC, dorsolateral prefrontal cortex; FL, frontal lobe; FWM, frontal white matter; HC, healthy control; lt., left; MPFC, medial prefrontal cortex; MRS, magnetic resonance spectroscopy; MTL, medial temporal lobe; NA, not applicable; NAA, N-acetylaspartate; NHC, non-healthy control; NS, nonsignificant; OC, occipital cortex; OCD, obsessive-compulsive disorder; OFA, orbitofrontal area; OFWM, orbitofrontal white matter; PC, parietal cortex; PMFC, posterior frontal cortex; PWM, parietal white matter; PL, parietal lobe; rACC, rostal anterior cingulate cortex; rt., right; TE, echo time; TR, repetition time; VOI, volume of interest.

^aNumber.

^bYale–Brown Obsessive Compulsive Scale.

^cThe schedule for affective disorders abd schizophrenia for school-age children—present and lifetime versions.