The long-term impacts of the Canterbury earthquakes on the mental health of the Christchurch Health and Development Study cohort

Abstract

Objective: Long-term studies following disasters are rare. It is important to quantify long-term effects of disasters to determine impacts on populations over time. We therefore aim to report the long-term associations between exposure to the Canterbury earthquakes and common mental disorders, taking into account potential confounding factors. Methods: The Christchurch Health and Development Study is a 40-year longitudinal study of a birth cohort of New Zealand children (635 males and 630 females). The Christchurch Health and Development Study includes 884 participants with data on earthquake exposure and mental health outcomes at ages 34 and 40 years. Rates of Diagnostic and Statistical Manual of Mental Disorders (4th ed.) disorders were measured categorically and using an expanded definition that included sub-syndromal symptoms. The current impact of the earthquakes is reported using 12-month prevalence data 7 years after the earthquakes. The cumulative impact of the earthquakes over the 7 years since onset is also reported. Results: There was a linear trend towards increasing rates of disorder with increasing exposure to the earthquakes. After adjusting for covariates, the 12-month prevalence of anxiety disorder symptoms was significantly increased (p = 0.003). The earthquakes were also associated with cumulative increases in symptoms of post-traumatic stress disorder (p < 0.001), anxiety disorder (p = 0.016), nicotine dependence (p = 0.012), and the total number of disorders (p = 0.039). Conclusion: The Canterbury earthquakes were associated with persistent increases in Anxiety Disorder symptoms 7 years after their onset. The earthquakes were also associated with cumulative increases in symptoms of common psychiatric disorders. The magnitude of these effects is small, may no longer be clinically significant and has decreased over time.