The research, published in the American Journal of Psychiatry, and funded by Wellcome, seeks to examine the causal effects of childhood maltreatment on mental health by accounting for other genetic and environmental risk factors, such as a family history of mental illness and socioeconomic disadvantage.
The first-of-its-kind research analysed 34 quasi-experimental studies, involving over 54,000 people.
Quasi-experimental studies can better establish cause and effect in observational data, by using specialised samples (eg. identical twins) or innovative statistical techniques to rule out other risk factors. For example, in samples of identical twins, if a maltreated twin has mental health problems but their non-maltreated twin does not, the association cannot be due to genetics or the family environment shared between twins.
Across the 34 studies, researchers found small effects of child maltreatment on a range of mental health problems, including internalising disorders (eg. Depression, anxiety, self-harm, and suicide attempt), externalising disorders (eg. alcohol and drug abuse, ADHD, and conduct problems), and psychosis.
These effects were consistent regardless of the method used or way in which maltreatment and mental health were measured.
The findings suggest that preventing eight cases of child maltreatment would prevent one person from developing mental health problems.
Corresponding author, Dr Jessie Baldwin from UCL Psychology & Language Sciences, said:
“It is well known that child maltreatment is associated with mental health problems, but it was unclear whether this relationship is causal, or is better explained by other risk factors.
“This study provides rigorous evidence to suggest that childhood maltreatment has small causal effects on mental health problems. Although small, these effects of maltreatment could have far-reaching consequences, given that mental health problems predict a range of poor outcomes, such as unemployment, physical health problems and early mortality.
“Interventions that prevent maltreatment are therefore not only essential for child welfare, but could also prevent long-term suffering and financial costs due to mental illness.”
Nevertheless, the researchers also found that part of the overall risk of mental health problems in individuals exposed to maltreatment was due to pre-existing vulnerabilities – which might include other adverse environments (eg. socioeconomic disadvantage) and genetic liability.
Dr Baldwin said: “Our findings also suggest that to minimise risk of mental health problems in individuals exposed to maltreatment, clinicians should address not only the maltreatment experience, but also pre-existing psychiatric risk factors.”
Marcus Munafò, Professor of Biological Psychology and MRC Investigator in the School of Psychological Science at the University of Bristol, added:
“Disentangling cause and effect relationships can be notoriously difficult, but is critical if we are to develop effective interventions to improve health. This study, which combined evidence from a large number of quasi-experimental studies, gives us the clearest evidence yet that childhood maltreatment is a cause of later mental health problems, but also that other genetic and environmental factors play a role.”
Researchers defined childhood maltreatment as any physical, sexual or emotional abuse or neglect before the age of 18.
Study limitations
Each of the quasi-experimental studies analysed may have been subject to potential biases. However, the findings were consistent across studies using different quasi-experimental methods, suggesting that the results are robust.
Additionally, it was not possible to draw firm conclusions about the specific effects of different types of maltreatment, as it is common for different types of abuse/neglect to happen at the same time, and studies rarely account for this.
The lack of available data mean that it was not possible to examine the effects of the timing of maltreatment, the interval between maltreatment and mental health issues, or differences between racial or ethnic groups. Future quasi-experimental research is needed to address these questions.
Paper
‘Childhood maltreatment and mental health problems: A systematic review and meta-analysis of quasi-experimental studies‘ by Jessie R Baldwin, Biyao Wang, Lucy Karwatowska, Tabea Schoeler, Anna Tsaligopoulou, Marcus R Munafo, Jean-Baptiste Pingault in American Journal of Psychiatry
