Yin 2004.

Methods	Allocation: "randomly assigned". Blinding: "double blind" "the sodium valproate and starch placebo were enclosed in capsule with same appearance, the interventions were coded by researchers as drug I and drug II". Duration: 6 weeks. Location: inpatients, China.
Participants	Diagnosis: Antipsychotics‐induced TD (Schooler criteria). Duration of TD: not reported. N = 80. Sex: 80 male. Age：mean 44 (SD 8) years old.
Interventions	1. Sodium valproate group: The initial dosage of sodium valproate was 0.2 g each time, three times per day; after 4 weeks if no adverse events, the dosage was titrated to 0.4 g each time, three times a day for 2 weeks, the treatment lasted for 6 weeks. N = 40. 2. Placebo group: starch capsule was the placebo treatment for 6 weeks. N = 40. All participants received stable doses of antipsychotics. Other concomitant medication was not reported.
Outcomes	TD clinical response. TD: AIMS. Mental state: BPRS. Adverse events: TESS, hypotension and disturbance of consciousness, leukocyte decrease, low platelet count.
Notes	Funding source: not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	....."randomly assigned…", no further details
Allocation concealment (selection bias)	Unclear risk	The author did not state the method of allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	....."double blind" "the sodium valproate and starch placebo were enclosed in capsule with same appearance, the interventions were coded by researchers as drug I and drug II" : Blinding of participants and key study personnel ensured.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	One participant in the treatment group left the study early.
Selective reporting (reporting bias)	Unclear risk	Unclear if all outcomes have been reported.
Other bias	Low risk	None obvious.

TD ‐ tardive dyskinesia

TD scales
 AIMS ‐ Abnormal Involuntary Movement Scale.
 BRS ‐ Barnes & Kidger Rating Scale.
 GRS ‐ Gerlach Rating Scale.
 SEPS ‐ Smith Extrapyramidal Scale.
 SRS ‐ Simpson Rating Scale.

Global state scales
 CGI ‐ Clinical Global Improvement

Mental/behaviour state scales
 BPRS ‐ Brief Psychiatric Rating Scale
 NOSIE ‐ Nurses Observation Scale for Inpatient Evaluation

General scales
 TESS ‐ Treatment Emergent Symptom Scale

Medication abbreviations
 CPE ‐ chlorpromazine equivalent dosages
 GVG ‐ Gamma‐vynil GABA
 SV ‐ Sodium valproate
 THIP ‐ tetrahydroisoxazolopyridinol