Methods	Allocation: random, no further details. Blindness: single, no further details. Duration: 24 weeks. Design: parallel. Location: not described. Country: not reported.
Participants	Diagnosis: chronic schizophrenia. N=80. Age: mean ~ 50.2 years, range not described. Sex: 39M, 41F. History: duration illness not described, age of onset not described. Setting: not described.
Interventions	Amisulpride: dose range not described, mean dose not described, fixed/flexible dose not described. N=40. Olanzapine: dose range not described, mean dose not described, fixed/flexible dose not described. N=40
Outcomes	Leaving the study early: any reason. Cognitive functioning: Wisconsin card sorting test. Unable to use - Mental state: BPRS change (no data). Adverse effects: BAS, SAS, UKU (no data).
Notes	There are control groups without further details provided.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Adequate sequence generation?	Unclear risk	Random, no further details.
Allocation concealment?	Unclear risk	No further details.
Blinding? Objective outcomes	Low risk	Objective outcomes such as laboratory measures or death are unlikely to have been much affected by problems of blinding
Blinding? Subjective outcomes	Unclear risk	Single, no further details. Whether blinding was successful has not been examined, but both compounds differ quite substantially in side-effects. This can be a problem for blinding
Incomplete outcome data addressed? All outcomes	Low risk	The rate of leaving the study early was low (5%), data on reasons for drop-out were provided. All data were analysed on an intent to treat basis with the last-observation-carried forward-method. This method is not perfect, but due to the very low attrition, the risk of bias was low
Free of selective reporting?	High risk	The study is only available as an abstract. Data on BPRS and EPS scales were not available
Free of other bias?	Unclear risk	Insufficient data to judge on baseline imbalance or industry sponsoring