Main findings

Although previous research has shown that exposure to childhood adversity is associated with a substantial increase in the risk of suicide ideation and suicide attempts as well as suicide, the association between cumulative exposure to childhood adversity and suicide risk has been less clear.167844 Our study of 548 721 individuals confirms that exposure to childhood adversity is associated with a substantially increased risk of suicide in adolescence and young adulthood and shows that the risk grows higher with increasing number of adversities. The association between adversity and suicide remained after adjustment for parental education and income, school performance, and childhood psychopathology. Exposure to suicide in the family, parental psychiatric disorder, and substantial parental criminality during childhood seem to entail greatest risks of later suicide. Moreover, childhood adversity seems to be such a strong risk factor for suicide in adolescence and young adulthood that it attenuated the effect of other known risk factors, such as poor school performance and childhood psychopathology. Childhood adversity, especially accumulated, increased the risk of suicide independently of these factors in our study.

In line with previous findings,394546 suicide in the family, parental psychiatric disorder, and parental criminality were associated with greatest suicide risk. For instance a Danish case-control study of 496 young people (aged 10-21) who died by suicide found several parental factors to be associated with an increased risk, such as parental suicide or early death, admission to hospital for a mental illness, unemployment, and low income.10

Previous studies have found a dose-response relation between childhood adversity and suicide attempts and between childhood adversity and premature death1622—that is, the higher the number of indicators, the higher the risk. We found this to also be true for suicide mortality.

Experience of childhood adversity increases the risk for disturbed emotional and behavioural self regulation, which could increase the risk for an impulsive and destructive reaction to stress and adversities in adulthood.47 This could, at least partly, explain the relation between childhood adversity and suicide risk. Furthermore, shared environment effects such as abuse or transmission of psychopathology are other possible explanations.48 We have previously shown childhood adversity to be associated with an increased risk of self harm,21 which in turn is a strong risk factor for suicide.1349 We have also shown that young people with childhood adversity are more likely to have used psychiatric services50 compared with those without such adversity. This is probably because they have higher rates of psychiatric disorders.51 Young people exposed to childhood adversity might, nevertheless, be less likely to seek medical care when ill compared with non-exposed children, which might influence their risk of suicide. It is not known how childhood adversity might have influenced help seeking behaviour and use of psychiatric services among young people in our study.

Exposure to childhood adversity is possibly influenced by genetic factors—for example, those related to family history of suicide, parental criminality, psychiatric disorders, and substance abuse among parents—which could also entail a higher likelihood for suicide in exposed children.52 Adjustment for parental psychiatric disorders, a proxy for children’s genetic loading for psychiatric disorders, however, attenuated but did not explain the associations between childhood adversity and suicide. This finding is in favour of a social causation hypothesis for the association we found between childhood adversity and suicide.

Although childhood adversity was common in our cohort, it is important to note that most children (58%) did not experience any adversity, and 41% (175/431) of suicides during follow-up were in those with no exposure to adversity. Thus, identification of risk factors for suicide in young people other than the adversities we studied remains a challenge but also an opportunity for suicide prevention in the younger age groups. For example, factors such as abuse and neglect, bullying, mood disorders and substance abuse, physical illness, lack of social support, and exposure to peers with suicidal behaviour might be important targets for prevention53 but were not studied here.

Furthermore, we found that those with a history of exposure to childhood adversity more often performed worse in school and also had a history of childhood psychopathology to a greater extent. In the light of previous evidence that children from adverse family backgrounds tend to show school performance below their potential, based on their cognitive capacity,54 programmes aimed at boosting school performance and providing social support to disadvantaged children could prove one promising pathway for improved mental health and suicide prevention. Moreover, a chaotic household seems to increase the suicide risk among young people, and previous findings have identified family support as an important intervention target to decrease suicide risk among anxious young people.55 Family support and involvement in intervention for those at risk is another potentially successful pathway.56 Lastly, the fact that indicators of childhood adversity often co-occur might have important implications for intervention. Prevention of single indicators among individuals exposed to several is unlikely to have any effects, and universal public health policies aiming to reduce social disadvantage and its impact on children lives are warranted.

Furthermore, the strong associations we found between single childhood adversities and suicide suggest that efforts should also be made to develop selective interventions that effectively alleviate suicide risk in easily identifiable groups at high risk. For example, children exposed to family suicide constitute a relatively small subgroup of all children with childhood adversity in our study but could be easily identified through school, the healthcare system, or social services, all of which are potential arenas for evidence based preventive interventions.