Abstract
Conflict and containment are the most frequently reported incidents in acute mental health care settings. This systematic review seeks to examine and synthesise existing evidence on the association between nurse staffing levels, nursing skill-mix and the occurrence of these incidents in acute mental health wards. Systematic review of quantitative studies examining nurse staffing levels and skill-mix (proportion of nursing shift that are registered or experience levels). Searches were undertaken in CINAHL, Cochrane, Embase, MEDLINE, PsycINFO, SCOPUS and Web of Science. Thirty-five observational studies were reviewed, including 32 on staffing levels (44 analyses) and 12 on skill-mix (14 analyses). Nine analyses found that higher staffing levels were associated with a reduction in reported conflict and containment incidents, while nine found lower staffing levels were associated with reduced incidents. Twenty-six studies found no significant association. For skill-mix, six analyses found that higher skill-mix was associated with a reduction in incidents, seven found no significant association, while one analysis showed reduced skill-mix was associated with a reduction in incidents. The results from analyses are mixed, with no clear conclusions on the relationship of staffing on incident rates. Studies often rely on routine or staff-reported data that are prone to measurement and observer bias, where most analyses did not control for important factors, e.g., patient case-mix or other patient-related factors which could have influenced the results. Although higher staffing levels are sometimes associated with increased incident reporting, this may reflect greater interaction and reporting, or residual (unmeasured) confounding and/or lack of control for mediators and effect modifiers. The review highlights the need for better risk adjustment in observational studies, more refined methodologies and clearer definitions of outcomes to guide workforce planning and policy. Further large-scale research is necessary to understand the complex relationships between staffing, skill-mix and safety in mental health care. There is a major staffing crisis in mental health nursing, but evidence to understand the impact of this on patient outcomes and to guide staffing policies is missing, with several significant limitations in the existing evidence that need to be resolved. Identified evidence on mental health nurse staffing levels and skill-mix is mixed and inconclusive; therefore, no clear implications for workforce planning or deployment can be recommended. However, this prompts debate on the nature and efficacy of routinely collected patient outcomes in clinical practice.