Introduction Workplace violence (WPV) towards healthcare workers (HCWs) employed in psychiatric wards (PWs) represeants a concern for healthcare organisations, globally. To date there is a lack of scientific data about the relationship between work-shifts and the occurrence of WPV against PW HCWs. The aim of the present study was to investigate the relationship between work shift schedules and WPV among registered nurses (RNs) working on non-traditional shifts, including nights and 12 hour shifts.

Methods The authors conducted a cross-sectional nested case-control analysis of data regarding the episodes of WPV perpetrated by patients or their relatives against RNs employed in two PWs, in the period between January–December 2016.

Results The one-year incidence of WPV was 31,50 per 100 Full Time Equivalent (FTE) positions. Cumulative nightshifts were significant for 3 or more nightshifts compared to working less than 3 nightshifts during the 7 days prior to the occurrence of WPV; additionally, RNs working 9 or more night-shifts showed higer risk of experiencing WPV compared to RNs working less than 4 night-shifts in the previous 28 days.

Discussion In the present study the occurrence of WPV against PW RNs was significantly correlated with shift- work; as consequence, the findings support the need of organisational interventions aimed at preventing the WPV and targeted on the management of shift-work schedules, with the aim of:

• limiting the night shifts up to two per week and up eight per month;

• adopting constant forward–rotating shift schedules.