C +sulpiride 2006.

Methods	Allocation: randomised (as stated in the abstract only, there is no description in the full text at all). Blinding: not stated. Duration: 8 weeks. Setting: unclear if it's inpatients or community. Design: parallel. Country: China.
Participants	Diagnosis: schizophrenia (CCMD‐III). N = 64. Age: 16‐60 years. Sex: male and female. History: length of illness: 8.48 ± 5.42 years in combination group; 8.79 ± 6.73 years in clozapine group.
Interventions	Combination therapy: clozapine (25 mg, twice a day) + sulpride (200‐600 mg/d) (N = 32). Monotherapy: clozapine: 25 mg, twice a day (N = 32).
Outcomes	‐ Usable data ‐ Clinical response: not clinically improved. Mental state: SANS. Adverse events: weight gain.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised, no further information.
Allocation concealment (selection bias)	Unclear risk	Not stated.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It is unclear if there are incomplete outcome data.
Selective reporting (reporting bias)	Low risk	All measured outcomes were reported.
Other bias	Low risk	None obvious.