Quetiapine 2010.

Study characteristics
Methods	Randomisation: sequence by computer, fixed block size of four without stratification. Allocation: AstraZeneca prepared individually numbered sets of study drugs, packed them according to the randomisation sequence and then shipped them to the study team in numbered but apparently identical sets. Blinding: identical capsules, "investigators, patients and all research staff were blind to the study drugs and the block size". Duration: 1 year. Design: parallel. Location: single‐centre (all in Early Assessment Service for Young People with Psychosis (EASY) in Hong Kong). Setting: outpatient.
Participants	Diagnosis: schizophrenia and related  psychoses (DSM‐IV), all first episode, all well remitted, all had remained well on maintenance medication for 1 year. N = 178. Gender: 80 men, 98 women. Age: 24.2 years. History: duration stable‐ 1 year, duration ill‐ 2.3 years, number of previous hospitalisations‐ 0 (first episode), age at onset‐ 21.9 years, severity of illness‐ mean PANSS 36, baseline antipsychotic dose‐ 153 mg/day chlorpromazine equivalents.
Interventions	1. Drug: quetiapine. Fixed dose of 400 mg/day. N = 89. 2. Placebo: duration of taper (days): 35. N = 89. Rescue medication: antipsychotics not allowed.
Outcomes	Examined Relapse: (i)  an increase in at least one of the following PANSS psychotic symptom items to a threshold  score (delusion, hallucinatory behaviour, conceptual disorganisation, unusual thought content, suspiciousness; (ii) Clinical Global  Impression Severity of Illness 3 or above and (iii) CGI  change 5 or above). Leaving the study early. Rehospitalisation. Suicide attempts. Adverse effects: akathisia, tardive dyskinesia, tremor, sedation, weight gain. Open employment status.
Notes	Supported by investigator initiated trial award from AstraZeneca.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sequence by computer, fixed block size of four without stratification.
Allocation concealment (selection bias)	Low risk	AstraZeneca prepared individually numbered sets of study drugs, packed them according to the randomisation sequence and then shipped them to the study team in numbered but apparently identical capsules.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Identical capsules, "investigators, patients and all research staff were blind to the study drugs and the block size".
Blinding (performance bias and detection bias) Subjective outcomes	Unclear risk	Identical capsules, "investigators, patients and all research staff were blind to the study drugs and the block size".
Blinding (performance bias and detection bias) Objective outcomes	Low risk	Identical capsules, "investigators, patients and all research staff were blind to the study drugs and the block size".
Incomplete outcome data (attrition bias) All outcomes	High risk	72% of the participants left the study early. As most participants dropped out after relapse this outcome was not affected, but it is a source of bias for other outcomes. Survival analysis for the primary outcome relapse.
Selective reporting (reporting bias)	Low risk	No evidence for selective reporting.
Other bias	Low risk	No clear other bias.