Huang 2013.

Study characteristics
Methods	Double‐blind randomised controlled trial
Participants	Diagnosis: DSM‐IV major depressive disorder; score ≥ 18 score on HRSD‐17 N: 40 Age: sarcosine group M = 37.2 (SD = 11.3); citalopram group M = 35.7 (SD = 9.5) Sex: sarcosine group 30% female; citalopram group 45% female Baseline depression severity: Sarcosine group HRSD = 23.7 (SD = 5.8); citalopram group HRSD = 24.5 (SD = 5.3)
Interventions	6 weeks of treatment. The dose was initiated at 1 capsule per day in the first 2 weeks, and titrated to 1 capsuletwice daily in weeks 3–4, and 1 capsule in the morning and 2 capsules before sleep in weeks 5–6 if clinically indicated Sarcosine (N = 20) 500 mg capsules Citalopram (N = 20) 20 mg capsules Concomitant treatment: no, patients had to be at drug‐free for over 3 months to enter trial
Outcomes	HRSD GAF Remission (score < 7 on HRSD) Response rate (≥ 50% reduction in HRSD scores) CGI‐S Adverse events
Notes	No other potential sources of bias identified
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: ''Patients were randomly assigned in blocks of six subjects to receive citalopram or sarcosine in a 1:1 ratio''
Allocation concealment (selection bias)	Low risk	Quote: ''Medication was provided in coded containers''
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: ''Patients, caregivers, and investigators (except the investigational pharmacist) were all masked to the assignment. Medication was provided in coded containers''
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: ''investigators...were all masked to the assignment''
Incomplete outcome data (attrition bias) All outcomes	Low risk	Dropout rate at each time point is recorded
Selective reporting (reporting bias)	Unclear risk	Protocol unavailable. Data reported matches methods
Other bias	Low risk	No other potential sources of bias identified