['To study the association between bed occupancy in psychiatric wards and rate of adverse incidents (AIs) including aggressive behavior and falls.', "This is a retrospective study analyzing bed occupancy and AIs' data in 4 closed wards in a state psychiatric hospital in Israel over a 20-month period. Ward-level daily records were extracted from the hospital's electronic admission-discharge and AI registries, creating a log of 609 days for each of the 4 wards. Relationships between gross and net bed occupancy and AIs rate were calculated, in general and for each ward and type of incidents.", 'Average gross occupancy was 106±14.8% and net occupancy was 96.4±15.6%. Gross occupancy >100% was recorded in 51% of days. Net occupancy was higher on days with at least 1 incident than on no-incident days (98.6±14.8% vs. 95.7±15.7%, P<0.0001). AIs occurred in 18.6% of days in the lowest occupancy quadrant (up to 85% occupancy), compared with 26.7% of days in the highest occupancy quadrant (106% and above). Moreover, aggressive behavior-type incidents were significantly lower in the lowest occupancy quadrant days compared with the highest occupancy quadrant (8.3% vs. 14.1%, P<0.01). Evidence of a dose-response effect of bed occupancy on AIs rate was found.'] Is overcrowding in Psychiatric Wards Associated With Increased Risk of Adverse Incidents?