Prevalence and predictors of post-traumatic stress symptoms in 2200 hospitalised and non-hospitalised injured New Zealanders

Objective: Post-traumatic stress disorder following injuries unrelated to mass casualty events has received little research attention in New Zealand. Internationally, most studies investigating predictors of post-injury post-traumatic stress disorder focus on hospitalised patients although most survivors are not hospitalised. We compared the prevalence and predictors of symptoms suggestive of post-traumatic stress disorder 12 months following injury among hospitalised and non-hospitalised entitlement claimants in New Zealand's Accident Compensation Corporation. This government-funded universal no-fault insurance scheme replaced tort-based compensation for injuries in 1974 since when civil litigation (which can bias post-traumatic stress disorder estimates) has been rare.

Methods: A total of 2220 Accident Compensation Corporation claimants aged 18-64 years recruited to the Prospective Outcomes of Injury Study were interviewed at 12 months post-injury to identify symptoms suggestive of post-traumatic stress disorder using the Impact of Events Scale. Multivariable models examined the extent to which baseline sociodemographic, injury, health status and service interaction factors predicted the risk of post-traumatic stress disorder symptoms among hospitalised and non-hospitalised groups.

Results: Symptoms suggestive of post-traumatic stress disorder were reported by 17% of hospitalised and 12% of non-hospitalised participants. Perceived threat to life at the time of the injury doubled this risk among hospitalised (adjusted relative risk: 2.0; 95% confidence interval: 1.2-3.2) and non-hospitalised (relative risk: 1.8; 95% confidence interval: 1.2-2.8) participants. Among hospitalised participants, other predictors included female gender, Pacific and 'other' minority ethnic groups, pre-injury depressive symptoms, financial insecurity and perceived inadequacies in healthcare interactions, specifically information and time to discuss problems. Among non-hospitalised survivors, predictors included smoking, hazardous drinking, assault and poor expectations of recovery.

Conclusion: One in six hospitalised and one in eight non-hospitalised people reported post-traumatic stress disorder symptoms 12 months following injury. Perceived threat to life was a strong predictor of this risk in both groups. Identifying early predictors of post-traumatic stress disorder, regardless of whether the injury required hospitalisation, could help target tailored interventions that can reduce longer-term psychosocial morbidity.