Child abuse cases in Hong Kong have surged by 60 percent over the past four years, and childhood trauma can have lifelong impacts. A groundbreaking study from the University of Hong Kong's (HKU) Faculty of Medicine has, for the first time, provided direct evidence that childhood maltreatment leaves lasting "genetic markers" of trauma, which significantly increase the lifetime risk of developing psychiatric disorders, including schizophrenia and ADHD. This discovery offers crucial evidence for developing more precise early intervention and prevention strategies.
A research team from the Department of Paediatrics and Adolescent Medicine at HKU's School of Clinical Medicine integrated large-scale databases from the UK Biobank and the Psychiatric Genomics Consortium. By analyzing genetic data from over 500,000 individuals, they have provided the first direct evidence that child abuse leaves long-term "markers" on the human genome, which in turn directly lead to a dramatically increased risk of schizophrenia and ADHD. The study found that childhood maltreatment substantially elevates the risk for the following mental illnesses:
The team revealed that childhood maltreatment significantly raises the risk for multiple psychiatric disorders.
The long-term epigenetic markers caused by child abuse are located near genes associated with neurodegenerative diseases and may be difficult to reverse. Therefore, preventing abuse remains the most fundamental measure to protect children.
The World Health Organization classifies child abuse as a global public health challenge, encompassing physical abuse, psychological abuse, sexual abuse, and neglect. The issue is also a serious concern in Hong Kong. According to data from the Social Welfare Department, newly reported child abuse cases soared from 940 in 2020 to 1,504 in 2024, representing a sharp 60 percent increase. Abused children are prone to warning signs during development such as social difficulties, attention deficits, and aggressive behaviors. If not identified and addressed promptly, these can easily deteriorate into severe mental illnesses.
The most critical finding of the study lies in revealing how abuse leaves "permanent scars" at the biological level. Child abuse leads to epigenetic changes known as "DNA methylation," akin to engraving long-term "markers" on the genes. Doctor Brian Chung Hon-yin, Clinical Associate Professor, Department of Paediatrics and Adolescent Medicine, School of Clinical Medicine, HKUMed, explained: "Previous studies relied on questionnaires and follow-ups, which were easily confounded by environmental factors. For the first time, we have used genomics to objectively demonstrate how childhood trauma sows the seeds of future illness at the biological level." From thousands of markers, the research team pinpointed 10 abnormal sites involving 9 key genes. Among them, three genes—CLU, MAPT, and HNRNPK—are closely linked to Alzheimer's disease, Parkinson's disease, and other cognitive impairments.
This suggests childhood maltreatment may impact shared biological pathways for both psychiatric and neurodegenerative disorders.
The study also points out that the impact of child abuse can be mitigated by addressing three categories of "modifiable factors" to lower mental illness risk:
Chung further explained that while the epigenetic markers caused by abuse may be hard to reverse, taking measures targeting these modifiable factors—by improving behavior, enhancing cognitive abilities, and providing educational support during a child's development—can effectively reduce the risk of future mental illness. The team hopes that in the future, by identifying specific DNA methylation markers, it may be possible to develop early biomarker screening tools and drug therapy targets to reduce disease risk at its source.
Schizophrenia is a condition caused by brain changes. Due to abnormal functioning in the brain's neural networks, patients experience disturbances in "thought" and "perception," which may also lead to speech and behavioral disorganization. These abnormalities are associated with overactivity of the brain chemical dopamine. Symptoms vary widely from person to person. Beyond "positive symptoms" like delusions and hallucinations, patients may also experience cognitive symptoms and negative symptoms. Approximately 1 percent-2 percent of the population may develop schizophrenia-spectrum disorders, with onset typically occurring between the ages of 20 and 30.
Five Categories of Schizophrenia Symptoms:
In the months or even years before a full episode, patients may exhibit prodromal symptoms such as insomnia, suspiciousness, and difficulty concentrating. Emotional changes like depression, anxiety, and irritability may also appear. Their social life, academic performance, or work ability may decline, and their personality or psychological state may change. These early signs can be subtle and overlap with other psychiatric conditions. If such symptoms are noticed, seeking medical advice early is crucial.
Following treatment, most patients gradually recover. The recovery process varies, and some residual symptoms may persist. For some, negative symptoms may become more prominent during this stage. Therefore, during the recovery or residual symptom phase, the focus should be on rehabilitation therapy and preparing for relapse prevention.
