Main findings

This study compared the prevalence and correlates of violent and non-violent crime victimisation among people with SMI with a general population control group, and compared impact and disclosure of victimisation. In total, 40% of the patient group compared with 14% of the control group were victims of a crime in the preceding year. Our primary hypothesis that patients would be at increased odds of personal and household crime compared with the general population controls was supported; those in the patient group were five times more likely to be victims of assault, and three times more likely to be victims of household acquisitive crime and criminal damage, after adjusting for sociodemographics and area characteristics. Women with SMI were at particularly high risk of violence, both community and domestic. Our secondary hypothesis that social deprivation, substance misuse and violence perpetration would account for any excess risk of violence victimisation among patients was supported among men with SMI but not among women with SMI (who had eight-fold adjusted odds). Our secondary hypotheses on impact and reporting of crime were partially supported: crime led to greater reported psychological adversity and injury by the victims in the patient group than those in the control group, but surprisingly patients and controls were equally likely to report victimisation to the police.

Findings in the context of past studies

Previously published studies on violence victimisation among people with SMI have had highly heterogeneous settings, populations and measures and have reported prevalence estimates ranging from 4% to 58%. ^{Reference Maniglio12–Reference Hiday, Swanson, Swartz, Borum, Wagner and Hiday16} Few studies have compared victimisation among mental health service users with a control group. ^{Reference Hughes, Bellis, Jones, Wood, Bates and Eckley17–Reference Sturup, Sorman, Lindqvist and Kristiansson21} Silver in the USA compared discharged psychiatric patients with a neighbourhood control sample, and found a two-fold increase in violence victimisation after adjusting for sociodemographics and violence perpetration. ^{Reference Silver19} Teplin et al in the USA and Sturup et al in Sweden compared violent crime against psychiatric patients with data from participants in national crime surveys and after adjusting for a very limited number of confounders found 12-fold and 6-fold higher risk among patients, respectively. ^{Reference Teplin, McClelland, Abram and Weiner18,Reference Sturup, Sorman, Lindqvist and Kristiansson21} Finally, a New Zealand birth cohort found that violent victimisation among a small number of people with schizophreniform disorder (n = 38) was three-fold higher than among those without any psychiatric disorder. ^{Reference Silver, Arseneault, Langley, Caspi and Moffitt20} The studies adjusted for a limited number of confounders and did not assess the impact or reporting of violence. Some past studies measured and reported on victimisation by any perpetrators, including partners and family members, ^{Reference Teplin, McClelland, Abram and Weiner18} but this is one of the few studies to report separately on domestic violence (perpetrated by partners and family members) and community violence (perpetrated by strangers or acquaintances). This is important, since these forms of violence have distinct interventions. ^{Reference Krug22} We found greatly elevated odds of victimisation compared with our general population control group for all violence types (physical and sexual; domestic and community), even after adjusting for a broader range of key individual, household and area characteristics than in studies carried out previously. ^{Reference Teplin, McClelland, Abram and Weiner18–Reference Sturup, Sorman, Lindqvist and Kristiansson21}

Our finding that women with SMI were particularly vulnerable to violence is consistent with evidence from Sweden and the USA. ^{Reference Teplin, McClelland, Abram and Weiner18,Reference Sturup, Sorman, Lindqvist and Kristiansson21,Reference Khalifeh and Dean23} In the general population, violence prevention among women is focused on domestic and sexual violence, ^24,25 but our finding that women with SMI had increased risks for both domestic and community violence suggests the need for broader interventions in this group.

We found that people with SMI are more likely to report adverse psychological and social effects once victimised. This would compound the personal, public health and economic costs of victimisation in this group, especially given the relatively large contribution of psychosocial impact to the overall economic cost of crime. ^{Reference Dubourg and Hamed26} These findings suggest that people with SMI should be prioritised in public health policies on violence prevention directed at vulnerable groups. Although SMI is uncommon, affecting around 3% of the population, ^{Reference McManus, Meltzer, Brugha, Bebbington and Jenkins27} it is one of the leading causes of global disease burden; and this study and others suggest that experiencing violence is associated with worse function and quality of life among this group. ²⁸

Past studies have shown that substance misuse, social isolation, homelessness and violence perpetration are important risk factors for victimisation among people with SMI; ^{Reference Dean, Moran, Fahy, Tyrer, Leese and Creed13,Reference Hiday, Swartz, Swanson and Borum29,Reference Teasdale30} whereas treatment adherence was protective. ^{Reference Hiday, Swartz, Swanson, Borum, Wagner and Hiday31} In our study, substance misuse and violence perpetration accounted for the excess risk of victimisation among men but not among women; suggesting the need for gender-sensitive interventions given the likely differences in risk pathways.

In routine clinical practice, victimisation is underdetected by mental health professionals, and where it is detected, concerns may not be promptly acted upon. ^{Reference Howard, Trevillion, Khalifeh, Woodall, Agnew-Davies and Feder32} Half of the violence victims in our study had unmet support needs. Mental health professionals need to identify victimisation, mitigate modifiable risk factors and address comorbidity.

Surprisingly, patients were as likely to report victimisation to the police and to progress through the Criminal Justice System as the general population, contradicting previous qualitative evidence that suggested people with mental health problems had limited access to the judicial system. ³³ Nonetheless, those in the patient group were less likely to be satisfied with the response of the police, with qualitative research conducted by the UK Charity Victim Support suggesting that they are often not believed and discriminated against within the Criminal Justice System. ^{Reference Pettit, Greenhead, Khalifeh, Drennan, Hart and Hogg34} Clearly criminal justice policies must protect against such discrimination. Half of patients had unmet support needs, including for practical/financial help, psychological support and help with the Criminal Justice System process.

Strengths and limitations

Strengths of this study include a large sample size, with a comparison group drawn from the same geographical area. We derived detailed information on the nature, impact and reporting of crime, and used self-reported measures for domestic and sexual violence (which have higher disclosure rates than interview measures). ^{Reference Walby and Allen35} The response rate was somewhat low at 52%. However, the study researched a sensitive topic, in a population which may have additional barriers to participating in such a study. Although domestic and sexual violence are sensitive topics for any group, they may be even more sensitive and complex for patients with SMI in secondary mental healthcare to discuss, since patients may worry about additional consequences of disclosure such as involuntary hospital admission. ^{Reference Pettit, Greenhead, Khalifeh, Drennan, Hart and Hogg34} We used a rigorous random sampling procedure, using a complete list of all patients on the caseload of included teams, whether or not they were actively engaged in treatment. As stipulated by the ethics committee, we recruited indirectly via care coordinators rather than through direct contact with patients. These factors may explain the lower response rate in this study compared with those using a convenience sample ^{Reference Hughes, Bellis, Jones, Wood, Bates and Eckley17,Reference Oram, Trevillon, Feder and Howard36} or direct recruitment of patients attending out-patient or in-patient services. ^{Reference Teplin, McClelland, Abram and Weiner18} Non-responders had the same demographic profile (in terms of age and gender) as participants. We did not have additional details on the characteristics of non-responders, so it is difficult to comment on the likely magnitude and direction of non-response bias. We speculate that some patients may have failed to respond because they had experienced or were experiencing violence and were worried about the consequences of disclosure (for example increased violence or coercive treatment), which would have led to an underestimate of violence prevalence. Others may have failed to respond because they did not have past experiences of violence and so did not perceive this study as relevant to them, which would have led to an overestimate of violence experiences. The overall effect is difficult to ascertain, but the odds ratios are sizeable and unlikely to be fully explained by non-response bias.

The findings have external validity, mirroring those of related studies in the USA and Sweden. ^{Reference Teplin, McClelland, Abram and Weiner18,Reference Sturup, Sorman, Lindqvist and Kristiansson21} There is potential for observer bias (since interviewers in the patient survey were not masked to the main hypothesis) and reporting bias (the patient and control groups may have different thresholds for disclosing victimisation), but this is mitigated by the highly structured questionnaire, and there is evidence that self-reported victimisation among people with SMI is valid and reliable. ^{Reference Teplin, McClelland, Abram and Weiner18,Reference Fisher, Craig, Fearon, Morgan, Dazzan and Lappin37,Reference Goodman, Thompson, Weinfurt, Corl, Acker and Mueser38} There may be a reporting bias for domestic violence because of the different interview settings – the controls were interviewed at home but most patients were interviewed in clinic, and disclosure may be easier in a clinical setting (although all home-based interviews were conducted in a private setting without others present, and participants themselves filled out a computer-based questionnaire in confidence).

Another limitation is the different sociodemographic profile of the patient and control groups, but we carefully adjusted for a broad range of individual and household measures. Our sensitivity analysis found no evidence for confounding by area of residence. Bias from missing data on impact is possible, but there was no evidence for this from our sensitivity analysis. A small proportion of the control group may have an SMI, since we used a self-reported measure to exclude mental illness in this group. However, the prevalence of SMI in the general population is less than 3%, ^{Reference McManus, Meltzer, Brugha, Bebbington and Jenkins27} and the presence of people with SMI in the control group would have led us to underestimate the relative odds. Findings on prevalence are likely to generalise to other Western urban settings with similar background levels of violence, and those on the relative risk of victimisation are likely to generalise to settings where people with SMI have a similar sociodemographic and clinical profile to the one described here.

In conclusion, victimisation among people with SMI is more prevalent and associated with greater psychosocial morbidity than victimisation among the general population. Our research has shown that women with SMI are at particularly high risk of both domestic and community violence. Violence prevention for people with SMI is likely to require an integrated response by mental health professionals, third-sector organisations and the Criminal Justice System.