The World Health Organization designated childhood maltreatment (CM) as a global public health challenge, encompassing various forms such as physical abuse, emotional abuse, sexual assault and neglect. The situation in Hong Kong is also cause for concern. According to the Social Welfare Department, newly reported CM cases surged from 940 in 2020 to 1,504 in 2024, representing a 60% increase. Against this backdrop, Hong Kong’s upcoming implementation of the Mandatory Reporting of Child Abuse Ordinance in January 2026 underscores the urgent need for enhanced child protection measures.
A research team led by the Department of Paediatrics and Adolescent Medicine, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, has conducted a pioneering study that established a causal link between CM and various neuropsychiatric disorders by integrating large-scale genomic datasets from the UK Biobank and the Psychiatric Genomics Consortium and analysing neuropsychiatric data from over 500,000 individuals and CM data from over 140,000 cases. The study was published in The British Journal of Psychiatry.
The findings revealed that individuals who had experienced CM face markedly elevated mental health risks: a five-fold increased risk of schizophrenia, an up to nine times higher risk of attention deficit hyperactivity disorder (ADHD), and nearly double the risk of major depressive disorder. At the biological level, the study discovered that CM leaves epigenetic markers on the genome known as ‘DNA methylation’. These markers, which can be influenced by environmental factors, lifestyle habits, and even psychological stress, represent long-term epigenetic scars triggered by CM. Among thousands of such markers, researchers pinpointed ten genetic locations near nine critical genes. Notably, three of these genes – CLU, MAPT and HNRNPK – are associated with neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and other cognitive disorders. The findings have provided the scientific evidence for developing more precise early intervention and prevention strategies.
Dr Brian Chung Hon-yin, Clinical Associate Professor of the Department of Paediatrics and Adolescent Medicine, who led the study explained, “Conventional studies rely primarily on long-term follow-ups and questionnaires, which are susceptible to confounding factors, such as one’s environment and social background. These confounders make it challenging to accurately evaluate the long-term impacts of CM, leading to a lack of strong evidence for policymaking and clinical intervention. Our team is the first to employ genomic and epigenomic methods, using a hypothesis-free approach to analyse how CM influences the brain and gene expression, thereby identifying opportunities for intervention and providing a foundation for prevention and treatment.”
Dr Chung added, “Our research demonstrates that CM can leave long-term genetic marks and affect genes related to neurodegenerative diseases. By identifying specific DNA methylation markers, we aim to develop early biomarker screening for high-risk populations in the future and even explore novel therapeutic targets for drug development to reduce disease risk at the source. This study serves as an important first step. Moving forward, we will apply the same rigorous methodology to systematically examine a broader spectrum of early-life adversities, such as abuse, neglect, and family dysfunction to comprehensively analyse their overall harm and long-term impact, ultimately seeking to drive societal awareness and action on the profound effects of early-life adversities on mental health.”
The study further revealed that the impact of CM extends beyond direct psychological harm. It increases neuropsychiatric risk through three mediating factors: addiction-related behaviours (such as smoking, prolonged screen time, and substance abuse), cognitive traits (like executive functioning, intelligence, and risk tolerance), and socioeconomic factors, such as educational attainment.
Dr Chung explained, “While the influence of these factors varies across different neuropsychiatric disorders, they are all modifiable. Interventions aimed at improving behaviours, enhancing cognitive ability, and providing educational support during development can effectively lower the risk. However, the long-term epigenetic markers left by CM are near genes associated with neurodegenerative diseases, and may be difficult to reverse. Therefore, preventing CM remains the most fundamental strategy for protecting children.”
