Measuring serious violence: comparison of police-recorded and self-reported data

Determining risk factors and consequences of serious violence requires accurate measures of violence. Self-reported and police-recorded offending are subject to different sources of bias.Our objectives were to compare risk of self-reported and police-recorded serious violence in late adolescence and early adulthood using linked UK birth cohort and police data, and to examine the association between cohort participation at different ages and police-recorded violence.We included individuals in the Avon Longitudinal Study of Parents and Children (ALSPAC) who had received fair processing materials and had not opted out of linkage to police records (n=12,662). Self-reported violence in the past year ranged from 5.3% (25 years) to 12.9% (20 years) among males and 3.2% (17, 22, 24 and 25 years) to 6.4% (18 years) among females. Police-recorded serious violence was lower at all ages, peaking at 17-18 years (1.7% among males, 0.5% among females). Study participation was lower among people who went on to have or had a record for police-recorded serious violence. At younger ages (in this case participation by mothers) this association was explained by socio-demographic and other factors.A key advantage of linkage to police records is it enables outcomes to be measured irrespective of study participation. However, police data undercounts serious violence. Further, observational studies may also underestimate violence as individuals with police-recorded serious violence are less likely to participate in research. Combining the two sources of data may overcome some of these issues, but careful thought would need to be given to the potential sources of bias present in each.