"Don't know" scores should be considered when assessing violence risk for youth in acute institutions.

Commonly, relevant information to score violence risk assessment instruments is missing at the time of assessment. While there are indications that lack of information to score items, or "Don't know" scores, has clinical relevance, these items are commonly omitted or treated as "No" scores in research. The Violence Risk Assessment Checklist for Youth (V-RISK-Y) is a screening instrument designed to identify violence risk in youth aged 12-18. The aim of this study is to assess whether "Don't know" scores on V-RISK-Y are associated with increased risk for registered violent events for youth during acute institutional stays as compared to "No" scores. This study utilized data from the V-RISK-Y multicenter study, consisting of a sample of 517 youth from child and adolescent psychiatry and residential youth care institutions. The following secondary analyses were performed: (i) the frequencies of "Don't know" and "No" scores for each item and registered violent events, and (ii) effect sizes from item-level logistic regression analyses of "Don't know" scores with "No" scores as reference, controlling for sex and type of institution. Findings show more registered violent events for youth during institutional stay when items were scored as "Don't know" as compared to "No". Nine of the 12 items had odds ratios (ORs) above 1 for "Don't know" for recorded violence when controlled for sex and type of institution. One item, "Lack of empathy", reached significance. The positive ORs indicate that "Don't know" scores may have clinical relevance despite not reaching statistical significance and that these scores should be considered both in clinical practice and in research.