Mass shootings and their impact on mental health
Mass shootings and other forms of mass trauma are increasing in frequency worldwide, and in recent years, there have been several attacks with religious and racial motivations˳4 Most of the evidence on the psychological effects has been reported from the USA, Europe and Scandinavia˳ Notable incidents in the USA include the killing of six worshippers during prayer at a Sikh temple in 2012,5 6 nine killed at a black church in 20157 and more recently the shooting of 11 Jewish worshipers at the Tree of Life Synagogue in Pittsburgh in 2018˳8 Elsewhere, 3 migrant school students were killed in Sweden in 2015,9 6 Muslim worshippers were killed during evening prayers in Canada in 201710 and 267 worshippers were killed by bomb attacks during Easter church services in Sri Lanka in April 2019˳11 One of the worst mass shootings fuelled by anti-immigrant, anti-Muslim sentiment occurred in July 2011 when 77 people, more than half of them teenagers, died in consecutive attacks at Utoya Island and Oslo, Norway˳12 This was a xenophobic, politically motivated attack inspired by liberal immigration policies, which was directed against the government and labour party youth˳4
Apart from the Norwegian massacre, the Christchurch shooting is the worst attack deliberately targeting Muslims in a Western context˳ Those exposed to this incident share a common faith but have a diverse ethnic and social composition, which is different from most previous groups˳ An important additional contextual factor in the Christchurch attack was the live streaming on social media, resulting in wider and repeated exposure to a demographically and geographically disparate audience, including children and adolescents˳
The psychological sequelae of exposure to violence is vast, with symptom trajectories varying over time and among different groups˳ A recent systematic review13 of 49 articles on samples of survivors and members of affected communities in the aftermath of 15 mass shooting incidents identified prevalence estimates of up to 91% for post-traumatic stress disorder (PTSD) and 71% for major depression˳ Individual responses can also include anxiety, grief, anger, sleep problems and somatisation symptoms˳ Factors known to predict adverse outcomes include demographic and preincident characteristics, such as female gender, preincident psychological symptoms and previous exposure to trauma˳ Similarly, event exposures, including greater proximity to the attack, acquaintance with the deceased, perception of life being in danger, panic or dissociative responses at the time, are also important˳ Postevent, risk factors for detrimental outcomes include individual psychological attributes, for example, emotion regulation difficulties, and psychosocial factors such as having less social support, or a change in psychosocial resources˳14
Although relatively little is known about the longer term psychological and emotional consequences of these experiences on individuals exposed to such events,15 potential prolonged and significant impacts have been increasingly noted in the literature, including in affected relatives˳15 16 Similarly, there is developing evidence that community-wide collective trauma can result from large-scale events and that the consequences may be more profound for those from collectivist cultures˳17 18
Gaps in the extant literature highlight the need for studies in the aftermath of high-impact events to include multiple waves of follow-up data in both exposed populations and those bereaved by the events13 to enhance understanding of the longitudinal patterns of responses and the processes that lead to chronic psychological symptoms˳ It is also desirable to include measures of positive outcomes (eg, resilience and post-traumatic growth)13 and, particularly important, when working with diverse populations, for assessments and interventions to be culturally and linguistically appropriate˳19 20
