How family income is associated with suicidal and violent behaviour in young adults
Authors: Sandra Feodor Nilsson, Merete Nordentoft
Journal: The Lancet Public Health (2018)

Self-harm and violent criminal behaviour can be common problems in young adults and adolescents and have adverse consequences on public health.1Hawton K Saunders KE O'Connor RC Self-harm and suicide in adolescents.Lancet. 2012; 379: 2373-2382Summary Full Text Full Text PDF PubMed Scopus (1155) Google Scholar, 2Sumner SA Mercy JA Dahlberg LL Hillis SD Klevens J Houry D Violence in the United States: status, challenges, and opportunities.JAMA. 2015; 314: 478-488Crossref PubMed Scopus (174) Google Scholar Self-harm is not just an expression of despair but also closely related to suicide,3Townsend E Self-harm in young people.Evid Based Ment Health. 2014; 17: 97-99Crossref PubMed Scopus (18) Google Scholar, 4Hawton K Bergen H Cooper J et al.Suicide following self-harm: findings from the Multicentre Study of self-harm in England, 2000–2012.J Affect Disord. 2015; 175: 147-151Summary Full Text Full Text PDF PubMed Scopus (201) Google Scholar which is a leading cause of death in young people.1Hawton K Saunders KE O'Connor RC Self-harm and suicide in adolescents.Lancet. 2012; 379: 2373-2382Summary Full Text Full Text PDF PubMed Scopus (1155) Google Scholar Also, the risk of violent crime conviction is increased in people who self-harm.5Sahlin H Kuja-Halkola R Bjureberg J et al.association between deliberate self-harm and violent criminality.JAMA Psychiatry. 2017; 74: 615-621Crossref PubMed Scopus (49) Google Scholar Exposure to violence is associated with increased risk of health problems,2Sumner SA Mercy JA Dahlberg LL Hillis SD Klevens J Houry D Violence in the United States: status, challenges, and opportunities.JAMA. 2015; 314: 478-488Crossref PubMed Scopus (174) Google Scholar such as suicidal behaviour, other mental health problems, and chronic physical disorders, and furthermore, interpersonal violence is a leading cause of death in young adults in the USA.2Sumner SA Mercy JA Dahlberg LL Hillis SD Klevens J Houry D Violence in the United States: status, challenges, and opportunities.JAMA. 2015; 314: 478-488Crossref PubMed Scopus (174) Google Scholar A link between parental socioeconomic status and offspring's risk of criminal behaviour6Sariaslan A Larsson H D'Onofrio B Langstrom N Lichtenstein P Childhood family income, adolescent violent criminality and substance misuse: quasi-experimental total population study.BrJ Psychiatry. 2014; 205: 286-290Crossref PubMed Scopus (32) Google Scholar and self-harm1Hawton K Saunders KE O'Connor RC Self-harm and suicide in adolescents.Lancet. 2012; 379: 2373-2382Summary Full Text Full Text PDF PubMed Scopus (1155) Google Scholar, 7Page A Lewis G Kidger J et al.Parental socio-economic position during childhood as a determinant of self-harm in adolescence.Soc Psychiatry Psychiatr Epidemiol. 2014; 49: 193-203Crossref PubMed Scopus (24) Google Scholar has previously been suggested, but whether changes in parental income during childhood are related to a change in the risk of these outcomes remains unanswered. To address this question, Pearl Mok and colleagues' interesting and well conducted study8Mok PLH Antonsen S Pedersen CB et al.Family income inequalities and trajectories through childhood and self-harm and violence in young adults: a population-based, nested case-control study.Lancet Public Health. 2018; 3: 498-507Scopus (27) Google Scholar published in The Lancet Public Health explores the association between parental income and the risk of self-harm and violent crimes in individuals in Denmark at ages 15–33 years. The nested case-control study included 21 267 individuals with a hospital-treated first episode of self-harm and 23 724 individuals with their first convictions for a violent crime. Parental income was measured in the year of the offspring's birth and at ages 5 years, 10 years, and 15 years. All included individuals were born between Jan 1, 1982, and Dec 31, 2000, and had two Danish-born parents who still resided in Denmark on the offspring's 15th birthday. The valuable nationwide Danish registers were constructively used, and each case was randomly age-matched and gender-matched to 25 controls with no experiences of the outcome. One of the most important findings was that children brought up in families with lowest income and who remained in this group throughout their childhood had the highest risk of both self-harm (incidence rate ratio [IRR] 7·2, 95% CI 6·6–7·9]) and violent offending (13·0, 11·9–14·1) compared with the reference group of children living in families with the highest income-level from birth until their 15th birthday. 8Mok PLH Antonsen S Pedersen CB et al.Family income inequalities and trajectories through childhood and self-harm and violence in young adults: a population-based, nested case-control study.Lancet Public Health. 2018; 3: 498-507Scopus (27) Google Scholar Notably, the longer the time spent in a low-income family environment, the higher the risk of both self-harm and violent behaviour later in life. Another remarkable finding was that children living in the most downwardly mobile family income group had higher risk of self-harm (IRR 2·3, 95% CI 2·1–2·6) and violent offending (2·9, 2·6–3·2) than those who were brought up in the most upwardly mobile group (IRR 1·6 [95% CI 1·4–2·0] for self-harm and 1·6 [1·3–2·0] for violent offending) when compared with the reference group of children consistently living in the highest family income environment. In other words, the relative risk of both outcomes was more greatly affected if the family became less affluent during childhood than if it became more affluent. The findings lead to the question "What is behind the social downwards mobility?". Several potential important confounders of the associations—ie, parental educational level and mental illness—were considered and were found to explain a substantial part of the association. However, the relative risk patterns remained. As in all other studies based on administrative data, risk of both residual confounding and overadjustment exists. Parental-related factors not considered in the study such as stressful life events, wellbeing, and experiences of self-harm and violent behaviour are likely to have a role in the observed associations. As the authors discuss, the strong associations are unlikely to be entirely explained by material resources, and the present study does not clarify the mechanisms behind the associations identified. However, future studies should certainly try to clarify this because such knowledge would have important implications for preventive work against self-harm and violent behaviour. As the authors mention, immigrants are likely to have even higher risks of both outcomes.9Webb RT Antonsen S Mok PL Agerbo E Pedersen CB National cohort study of suicidality and violent criminality among Danish immigrants.PLoS One. 2015; 10: e0131915Crossref PubMed Scopus (21) Google Scholar Whether the findings can be replicated in other cohorts, including minority groups, is a question of interest. The study has very important take-home messages from a prevention and public health perspective because with the use of refined, high-quality analyses, the study shows that a downwards as well as an upwards change in family-income and accumulation of poverty during childhood is closely related to young individuals' health and social behaviour. It is likely that the associations are even stronger in high-income countries with higher levels of social inequality than that seen in Denmark. Findings confirm the need for early interventions and improved efforts to support lower-income families.2Sumner SA Mercy JA Dahlberg LL Hillis SD Klevens J Houry D Violence in the United States: status, challenges, and opportunities.JAMA. 2015; 314: 478-488Crossref PubMed Scopus (174) Google Scholar, 10Nilsson SF Laursen TM Hjorthoj C Thorup A Nordentoft M Risk of psychiatric disorders in offspring of parents with a history of homelessness during childhood and adolescence in Denmark: a nationwide, register-based, cohort study.Lancet Public Health. 2017; 2: e541-e550Summary Full Text Full Text PDF PubMed Scopus (15) Google Scholar However, special focus should not be restricted to families experiencing absolute poverty. Awareness of the risk in children living in families with downwards-changing economic patterns is also highly important. Family and society are among the most important sources to address when aiming to improve young people's health and positive development.11Viner RM Ozer EM Denny S et al.Adolescence and the social determinants of health.Lancet. 2012; 379: 1641-1652Summary Full Text Full Text PDF PubMed Google Scholar However, improved interventions supporting socially disadvantaged families in high-income countries are needed. Such efforts could potentially lead to prevention of self-harm and violent behaviour. SFN is supported by Lundbeckfonden (number R264-2017-4008). The authors declare no competing interests. Family income inequalities and trajectories through childhood and self-harm and violence in young adults: a population-based, nested case-control studyParental income represents a multitude of unmeasured familial sociodemographic indices. Tackling the causes of inequality and associated psychosocial and sociocultural challenges to enable upwards socioeconomic mobility could potentially reduce risks for self-directed and externalised violence. Full-Text PDF Open Access