New research from the University of Auckland shows the lifelong toll that adverse events in childhood can take on your health. Poor mental health is almost three times more prevalent among people in New Zealand who experienced four or more "adverse childhood events" compared with people who experienced none, the research suggests.

The study covered eight types of childhood adversity: Emotional, physical or sexual abuse, and growing up in a household where there was violence, substance abuse, mental illness, divorce, or a household member behind bars. "Toxic stressors in childhood can take a lifelong toll on many aspects of our health," says Associate Professor Janet Fanslow, of the School of Population Health in the Faculty of Medical and Health Sciences. "The effects ripple across society to create a huge burden on family and whanau, our health service and the economy."

Experiencing even just one type of childhood adversity — such as having a household member in jail or witnessing interpersonal violence in the home — is associated with an increased risk of poor mental health, the study suggests. Experiencing two or more is associated with higher odds of disability, and four or more with chronic physical health problems.

Increased risks of health problems such as heart disease or asthma can be linked to specific types of adverse events, according to researchers led by Dr. Ladan Hashemi, also of the School of Population Health. The scientists analysed 2,888 responses to the 2019 New Zealand Family Violence Survey, which was carried out in Waikato, Northland, and Auckland.

The odds of heart disease rose for people who had experienced emotional or sexual abuse, witnessed interpersonal violence, or lived in a household where there was substance abuse. The odds of asthma increased for those from a household with substance abuse, mental illness or divorce.

International research shows how adversity in childhood can affect neurological and hormonal development, inflammation pathways, cognitive, social, and emotional competencies, and propensity for risky behaviours such as smoking or substance abuse. Socio-economic factors didn't fully explain the associations in the New Zealand study. "Policy and programmes to address child poverty are important in their own right, but will not fully mitigate the effect of adverse childhood experiences," write Dr. Fanslow, Dr. Hashemi, Dr. Pauline Gulliver, and Professor Tracey McIntosh in the research paper.

About 45% of the people in the study reported no adverse childhood events. A majority experienced at least one, and one-in-three reported more than one. In the study, a person's mental health was described as poor if they had been diagnosed with a long-term condition or had recently taken anti-depressants or sleeping medication. The paper, "Exploring the health burden of cumulative and specific adverse childhood experiences in New Zealand: Results from a population-based study," was published in the journal Child Abuse & Neglect. The findings "should provide impetus to establish widespread prevention and intervention initiatives," the academics write. "Strategies that address socioeconomic inequities are needed, but will not, of themselves, fully mitigate the consequences of adverse childhood experiences."