Widening Excess Mortality During the COVID-19 Pandemic in Individuals Who Self-Harmed

The impact of the COVID-19 pandemic on mortality has been under close scrutiny (Beaney et al., 2020). While some studies reported elevated COVID-19 mortality for at-risk individuals, (e.g., those with mental health conditions; Toubasi et al., 2021), others advocated evaluating total lives lost to capture potential detrimental effects associated with mitigations to curb its spread (VanderWeele, 2020). Mortality for individuals who self-harmed was higher than for the general population prior to the pandemic (Bergen et al., 2012). Data on change in mortality during the pandemic for this subpopulation are scarce. A recent study reported increased mortality for individuals hospitalized for self-harm during the pandemic in France (Jollant et al., 2021). However, the findings were limited by using only hospitalization data covering the early months of the pandemic and did not consider changes in mortality in the general population.

This study aimed to examine any changes in mortality difference before and during the COVID-19 pandemic for individuals who self-harmed compared to those who did not.

Methods

Measures

Mortality data were extracted from the Office for National Statistics death register and the Welsh Demographic Service data set (Table E1 in ESM 1). ICD-10 codes were used to group underlying causes of death into natural, unnatural (including suicide as a separate category), and unknown causes (John et al., 2018). Self-harm was identified from primary care, emergency department, and hospital admissions data using validated code lists (Marchant et al., 2020). We defined periods as Pre-C19 (October 2019–March 2020), Wave 1 (April 2020–September 2020), and Wave 2 (October 2020–March 2021; Figure 1). We extracted other covariates (e.g., sex and age) to analyze change in mortality (complete list in Table E2 in ESM 1).

Results

Among the 2,932,232 eligible individuals, we identified 45,422 and 2,558,599 individuals in the self-harm and no self-harm groups with 2,244 and 83,529 deaths, respectively (Table E3 and Figure E1B in ESM 1, see also Figure E3 in ESM 1 for the monthly trend of self-harm within the study period). We observed two peaks in monthly trends of crude rates of all-cause and natural-cause mortality associated with Wave 1 and Wave 2 for both self-harm and no self-harm groups (Figure E4 in ESM 1). After April 2020, we found a decreasing trend of unnatural-causes and suicide mortality rates, at the same time as an increasing trend of unknown-causes mortality rate. The decreases in mortality for both unnatural causes and suicide during the pandemic were more pronounced in the self-harm group.

After PSM (Table E3, Table E4, and Figure E5 in ESM 1, Results in ESM 3), 43,368 individuals from the self-harm group (95.5% of 45,422) were matched with the same number from the no self-harm group. Monthly trends of crude all-cause mortality rates showed peaks corresponding to Waves 1 and 2 for the self-harm group but not for the no self-harm group (Figure 1). RHRs were significantly greater than one for Wave 1 (RHR = 2.03, 95% CI: 1.04–4.03, p = .042) and Wave 2 (RHR = 2.19, 95% CI: 1.12–4.29, p = .023). Excluding the COVID-19 infection variable from the model revealed similar RHRs, and stratified analyses did not indicate significant subgroup differences although RHR was considerably higher for younger than 65 years (RHR = 3.85) than the older than 65 years (RHR = 1.75) age group in Wave 2 (Table E5, Table E6, and Figure E6 in ESM 1). RHRs from the robustness check were close to unity whereas RHRs from the sensitivity analysis that ascertained only the incident self-harm population to the self-harm group were still greater, but not significantly different from one (Table E5 in ESM 1). Without applying PSM (unmatched), RHRs were slightly reduced compared to the main analysis but were still statistically greater than one. The proportion of mortality for individuals who self-harmed during Wave 1 and Wave 2 was not significantly different from those who self-harmed in the prepandemic period (Table E7a and Table E7b in ESM 1).

Discussion

We, for the first time, observed a widening mortality gap between individuals who self-harmed and the general population over the COVID-19 pandemic between April 2020 and March 2021 in the United Kingdom. A French analysis showed an elevated all-cause mortality for individuals hospitalized for self-harm during the early months of the pandemic (Jollant et al., 2021). We employed PSM and DiD to balance characteristics between the self-harm and general population and account for baseline mortality risk following self-harm before the pandemic. However, correct model specification of propensity scores and no unmeasured confounding assumptions for PSM and DiD may not be easily verified. The negative findings from the sensitivity analysis using incident self-harm population may stem from smaller sample size and difference in time since first exposure to self-harm comparing incident to prevalent samples (Vandenbroucke & Pearce, 2015). Caution is required in interpreting our findings as longer-term consequences associated with COVID-19 (e.g., possible economic downturn; VanderWeele, 2020), were not captured. We found similar trends in unnatural-causes and suicide mortality, with a more pronounced reduction during the pandemic for individuals who self-harmed. Reduction of suicide rates during the pandemic has been reported in other countries (Pirkis et al., 2021). This decrease may be reflected in subsequent mortality of those who self-harmed, a robust risk factor for suicide. Increased unknown-cause mortality during the pandemic may potentially be partially explained by misclassification of suicide deaths (John et al., 2018) and the increased death registration delays due to COVID-19 for deaths, including suicides, which require coroners’ inquests (Office for National Statistics, 2021). Small numbers of deaths reduced statistical power and limited our ability to perform stratified analyses.

Our findings of a widening mortality inequality between individuals who self-harmed and the general population during the COVID-19 pandemic are concerning. Our data do not indicate elevated mortality following self-harm event(s) that occurred during the pandemic. Rather, the self-harm population might be more vulnerable to COVID-19-related adversities (risk of infection and comorbidities, reduced access to care). Timely policies, assessments, crisis pathways, and interventions for at-risk individuals are necessary to ensure those who self-harm receive effective support and to reduce inequalities. We revealed a discernible, albeit nonstatistically significant increase of mortality gap for individuals younger than 65 years compared to 65 years or older. We argue for more targeted interventions aimed at this working population and further research to focus on the at-risk social groups. The decline in self-harm-related contacts to health services during the pandemic found in this study and others may indicate the presence of unmet/unmanaged need that requires prompt attention (DelPozo-Banos et al., 2022). The co-occurrence of a widening mortality gap for individuals who self-harmed and the drop in self-harm-related contacts to health services in the general population during the pandemic needs further investigation. The dynamic nature of the pandemic requires timely data for mitigating relevant risk factors. Large-scale and long-term follow-up studies to monitor the effects of the pandemic on physical and mental health are warranted.

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