‘Huge’ proportion of mental health conditions in Australia found to be caused by childhood maltreatment

An Australian study has estimated the proportion of mental health conditions which are directly caused by childhood maltreatment and independent from other influences such as genetics and social environments. Photograph: ThitareeSarmkasat/Getty Images/iStockphoto

If child abuse and neglect did not exist, almost a quarter of the more than 1.8m cases of depression, anxiety and substance use disorders in Australia could be prevented.

The finding comes from the first Australian study to estimate the proportion of mental health conditions which are directly caused by childhood maltreatment and independent from other influences such as genetics and social environments.

Published on Thursday in the American Medical Association’s specialty journal of psychiatry, JAMA Psychiatry, the research led by the University of Sydney found 41% of suicide attempts, 35% of self-harm and 21% of cases of depression in Australia are caused by child maltreatment.

The researchers called for childhood abuse and neglect to be treated as a national public health priority, with investment in preventive policies such as paid parental leave, affordable childcare, or income support – all things which evidence shows reduce instances of maltreatment.

Childhood maltreatment includes physical, sexual or emotional abuse, and emotional or physical neglect experienced before the age of 18.

Dr Lucinda Grummitt, the lead author of the paper from the Matilda Centre for research, said: “Normally, the gold standard for establishing cause and effect in science is a randomised control trial – where we can randomly allocate participants to either exposure or control [not being exposed].

“But obviously, we could never allocate a child to abuse and neglect, and another one not, and then compare how they grow up.”

The researchers’ work was informed by a systematic review published in 2023 that synthesised the findings from international studies examining cause and effect through other study designs.

For example, there are twin studies, where the children share the same genetics but one child was adopted out, allowing researchers to control for the effect of genetics on maltreatment and mental health. Other studies examined the mental health consequences of institutional neglect that occurred in Romanian orphanages during the Ceaușescu regime.

Grummitt’s team then combined those causal estimates with Australian estimates of maltreatment to calculate the impact of abuse and neglect on specific mental health conditions such as anxiety, depression, harmful alcohol and drug use, self-harm, and suicide attempts.

One of the surprising findings was although the international evidence suggested a small to medium causal effect, Grummitt’s research found a “really huge” proportion of mental health conditions in Australia are caused by childhood maltreatment.

“In psychiatry we would never think of mental health conditions as having a single cause,” she said. But the study does isolate where childhood maltreatment has been attributed with creating a “latent vulnerability – it might predispose someone to experiencing mental health conditions, and then something that happens later on is that proximal cause of a disorder”, Grummitt said.

“These findings really highlight that we don’t need to be waiting until people are showing up to mental health treatment services to be able to help them.”

Prof Sarah Bendall, the head of trauma and youth mental health at Orygen, praised the “elegant” design and strong methodology of Grummit’s study.

“This research and the childhood maltreatment study are really putting the numbers behind what we see in clinical practice and showing us how important childhood maltreatment and childhood trauma are in the development of mental disorder,” Bendall said.

Carly Dober, a psychologist and director of the Australian Association of Psychologists, said childhood maltreatment can affect how people see themselves or the world.

“They might have difficulty trusting people, they might have difficulty forming and maintaining strong interpersonal relationships,” she said.

Dober said a lack of awareness around childhood maltreatment meant many people were unaware that what they experienced as a child was, in fact, abuse or neglect. “It can be very confusing for young people to talk about, and adults as well, who have lived through it.”