A 2026 analysis found that clozapine, paliperidone and olanzapine had the largest estimated reductions in hostility and aggression compared with placebo among the medicines studied. But the findings do not establish a strict ranking: confidence in every comparison was rated low or very low, and the three leading drugs were not statistically distinguishable from one another.
The findings come from an analysis of 41 studies drawn from 60 randomized trials involving 21,025 adults with schizophrenia. Participants had an average age of 38, and 60% were men. The analysis compared 18 antipsychotics with placebo, with each medicine studied as a single treatment and follow-up lasting at least 48 hours.
What the analysis found
The researchers used standardized mean differences, or SMDs, to compare changes in hostility and aggression ratings. More negative values indicated a larger estimated reduction compared with placebo.
- Clozapine: SMD −0.75, with a 95% confidence interval from −1.13 to −0.38.
- Paliperidone: SMD −0.62, with a 95% confidence interval from −0.88 to −0.36.
- Olanzapine: SMD −0.60, with a 95% confidence interval from −0.86 to −0.35.
Four other medicines—asenapine, risperidone, aripiprazole and haloperidol—also had confidence intervals below zero, with estimated effects ranging from −0.52 to −0.30. Quetiapine’s estimated effect was smaller, at −0.12, and was indistinguishable from placebo in the network. Cariprazine and lurasidone leaned toward benefit, but their confidence intervals crossed zero. Ziprasidone and amisulpride each had an estimated effect of −0.07, while brexpiprazole’s estimate was 0.02.
Why the results do not create a definitive ranking
The apparent differences between the top three medicines were not statistically significant. Clozapine’s estimated advantage over olanzapine was 0.15 SMD, with a confidence interval ranging from −0.19 to 0.49. Paliperidone and olanzapine differed by 0.01 SMD, with a confidence interval from −0.30 to 0.33.
The clozapine estimate also came from a much smaller group—124 people who received clozapine—than the olanzapine and paliperidone estimates, which included 2,423 and 1,936 people respectively. The researchers said paliperidone’s apparent advantage requires confirmation in direct, head-to-head trials.
The network itself showed significant inconsistency, meaning some connected comparisons did not fit together cleanly. A formal test produced p = 0.018, with eight specific inconsistent comparisons involving amisulpride or olanzapine. Trial-to-trial heterogeneity was moderate.
Hostility ratings are not the same as violent incidents
Most of the evidence measured changes in hostility scores rather than acts of violence. Thirty-five of the 41 studies used a single item or subscale from a general psychosis rating scale. Four used an aggression-specific scale, and only two counted actual aggressive incidents.
Thirty-four studies had some concerns about bias, and six were considered high risk. Common issues included aggression data collected after the original trial began and the potential effects of participant dropouts. The median follow-up was eight weeks, so the results provide limited information about longer-term outcomes.
People in first-episode and forensic settings were underrepresented, while people with substance-use problems were often excluded. Those differences matter because results from one clinical group may not apply equally to every person with schizophrenia or schizoaffective disorder.
How this fits with other evidence
A randomized 12-week trial involving 110 physically assaultive inpatients with schizophrenia or schizoaffective disorder reported greater reductions in aggressive behavior with clozapine than olanzapine, and with olanzapine than haloperidol. A 2018 meta-analysis of 18 randomized trials found a small advantage for second-generation antipsychotics over older first-generation medicines on hostility.
Separate Swedish register studies have reported lower rates of violent crime, arrests and convictions during periods when people were receiving antipsychotic treatment. Those findings were observational, however, and therefore cannot establish that medication alone caused the lower rates. The randomized trials were shorter and mostly assessed hostility ratings rather than criminal or violent behavior.
What the findings mean for treatment decisions
The analysis does not show that one antipsychotic is best for everyone, nor does it support changing treatment without clinical guidance. Medication decisions may need to account for side effects, tolerability, adherence, other health conditions and the person’s preferences.
Clozapine is described as requiring regular blood monitoring and is usually reserved for treatment-resistant schizophrenia. Olanzapine carries substantial weight-gain and metabolic risks. Long-acting injectable forms of paliperidone and risperidone may help some people maintain adherence, although there were too few injectable studies to determine whether these formulations affect aggression differently.
Quetiapine was not significantly different from placebo for hostility and aggression in this network, but that result does not mean it cannot help an individual patient. Differences between a trial average and a person’s response are important when clinicians and patients review treatment options.
Overall, the analysis suggests that several antipsychotics may reduce hostility in schizophrenia, with the largest estimated effects seen for clozapine, paliperidone and olanzapine. It does not provide a reliable league table, and most of the evidence concerns rating-scale hostility rather than violent acts.
AI tools were used to assist with the preparation of this article.
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