According to a new study in Denmark, children who are genetically predisposed to developing attention deficit/hyperactivity disorder (ADHD) and to struggling academically had a greater risk of being maltreated as children.
Hannah was restless, unfocused and quick to become angry. The symptoms pointed to a psychiatric disorder, but something deeper was going on. First, she was diagnosed with ADHD. Later, it emerged that she had been maltreated and neglected at home. It is impossible to say which came first – but researchers can now show that Hannah’s genetic risk for ADHD is associated with an increased risk of being exposed to maltreatment.
This is exactly what researchers from the Department of Biomedicine at Aarhus University found in a new study published recently in the respected journal JAMA Psychiatry.
The study shows that children with a genetic predisposition for ADHD and poor academic performance are more likely to experience maltreatment and neglect – regardless of any psychiatric diagnoses they may later receive. And if the child’s parents also have a psychiatric diagnosis, the risk roughly doubles, explains Ditte Demontis, Professor of Psychiatric Genetics at Aarhus University in Denmark, who led the study.
“Our hope is that this discovery will eventually help us to identify children with a higher risk of maltreatment more quickly and reliably – and ensure that both the children and their parents receive the help and support they need,” says Ditte Demontis.
What genes can tell us
The researchers uncovered the link by analysing genetic data and registry information from a large study involving 140,000 participants in Denmark. The study aimed to identify both biological and environmental risk factors for developing psychiatric conditions.
They examined five psychiatric diagnoses – ADHD, autism, bipolar disorder, depression and schizophrenia – and compared participants’ genetic profiles with records of exposure to childhood maltreatment in Denmark’s health registries. These registries include notes from psychiatrists and doctors who use ICD-10 codes to document many events, including physical violence and neglect, during their assessments of children.
For each participant, the team calculated a polygenic score – a measure of genetic load for a given disorder or condition based on many genetic variants with a small effect. Each variant contributes a tiny amount to the likelihood of developing a disorder such as ADHD or depression. Combined, they provide an overall picture of how genetically predisposed a person is to certain disorders or traits.
Among those with psychiatric diagnoses, the researchers then tested whether the polygenic scores were higher for children who had experienced maltreatment versus those who had not. Their analysis accounted for age, sex and other relevant factors.
The results showed that children with a high polygenic score for ADHD – and poor genetic predisposition for academic success – more likely experienced maltreatment or neglect in childhood regardless of the psychiatric diagnosis they had or later received.
When inheritance and vulnerability run in families
The researchers also divided participants into four groups based on their polygenic score for ADHD. Among children who had both an ADHD diagnosis and a high genetic score, the risk of having experienced maltreatment as a child was 6%. In contrast, the risk was just 1.2% among children without a psychiatric diagnosis – even if they had a high polygenic score for ADHD.
When the researchers added information about the parents’ psychiatric diagnoses, a clear pattern emerged: individuals with a psychiatric diagnosis, a high polygenic score for ADHD and parents with a psychiatric diagnosis had a 5.7% risk of maltreatment. But if the parents had no psychiatric diagnosis, the risk dropped to 2.5%.
“Our data suggests that a child’s genetic profile – which may be associated with increased disruptive behaviours – combined with the parents having a psychiatric diagnosis are two key factors that raise the risk of child maltreatment,” says Ditte Demontis. She notes that these two factors are often connected, since children inherit their genetics from their parents.
“Several previous studies have shown that the children of parents with a psychiatric diagnosis have a greater risk of maltreatment. What is new here is that the polygenic score for ADHD can help to identify children with increased risk – even among those whose parents also have a psychiatric diagnosis,” she says.
Statistics show patterns – not fates
The study reveals a statistical link between a certain genetic profile and an increased risk of childhood maltreatment – especially genetics associated with ADHD and academic difficulty. But this does not mean that a specific genetic profile inevitably leads to maltreatment. “These are risk factors and not causes,” says Ditte Demontis. “Social and family circumstances also play a major role.”
For people with psychiatric diagnoses, the study could not determine whether the diagnosis or the maltreatment came first. “In many cases, both were registered around the same time,” Ditte Demontis points out. “So, we cannot say whether a psychiatric diagnosis leads to maltreatment or vice versa.”
What is known is that each person’s genetic makeup is present from birth. That makes it useful for identifying innate predispositions to disease or specific behaviours. But in the context of childhood maltreatment, genetics is just one piece of a much larger puzzle. Even a high polygenic score does not predict how a child’s life will unfold – many other factors influence the risk of maltreatment.
That is why many children with high scores will never experience maltreatment – whereas others with low scores may still be affected. Social context has a key role. It could be hypothesised that parents who are coping with both mental illness and social problems may find caring for a very impulsive or troubled child especially challenging.
The findings also prompt reflection on how children with mental health problems have been viewed and treated historically. The focus has often been on the diagnosis itself – without considering the child’s full life circumstances and background.
“This study did not focus on pinpointing individual children,” says Ditte Demontis. “It focused on understanding when society should pay closer attention. In the future, we may be able to combine genetic and social data to better identify children at risk – and offer timely help to them and their families. Because maltreatment is never the child’s fault,” she says.
