The Spanish Flu pandemic and stable New Zealand suicide rates: historical lessons for COVID-19

There were initial concerns that the COVID-19 pandemic might significantly increase worldwide suicide rates, due to the combined effects of economic recession, rising unemployment, job insecurity, income shock, social isolation, possible barriers to receiving mental health treatment, increased alcohol use, strained relationships, increased levels of national anxiety and distress.^1,2 Also, if the COVID-19 pandemic were to trigger another 1929–1930s “Great Depression” and raise unemployment by potentially 15–20%, suicide rates could increase by at least 15%, with working age men being the highest risk group.¹ Stuckler et al³ reported that within European Union countries between 1970 and 2007, every 1% increase in unemployment rate was associated with a 0.79% increase in suicide rate for those aged under 65.

Pirkis et al⁴ recently published the early impacts of the COVID-19 pandemic on suicide rates in mainly high-income and upper middle-income countries. They found that suicide rates were either stable or reduced compared with the pre-pandemic period. Pirkis et al also analysed New Zealand suicide rates during the COVID-19 pandemic and found that there was a statistically significant decrease in New Zealand suicide rates in both primary analysis between 1 April and 31 July 2020 (rate ratio: 0·79; 95% CI: 0·68−0·91) and sensitivity analysis between 1 April and 31 October 2020 (rate ratio: 0.81; 95% CI: 0.72–0.90), compared with the pre-pandemic period.⁴

In the context of the unexpected fall in New Zealand suicide rates during the COVID-19 pandemic, we have investigated whether the early phase of a previous pandemic—the “Spanish Flu” pandemic of 1918–1920—was associated with decreased New Zealand suicide rates. If so, we hypothesise that the longer-term effects of the Spanish Flu pandemic on New Zealand suicide rates might be indicative of the longer-term effects of the COVID-19 pandemic on future New Zealand suicide rates.

The Spanish Flu (1918–1920) killed 40 million people worldwide (ie, 2.1% of the world population), equivalent to 150 million deaths at current world population levels.⁵ The significant estimated flu-generated worldwide gross domestic product (GDP) decline was c.6–8%.⁵ The Spanish Flu was also New Zealand’s most severe disaster event and is estimated to have killed 9,000 people.⁶

Methods

We obtained data from the World Health Organization⁷ in relation to New Zealand crude suicide rates (total, males, females) between 1909 and 1929. Using descriptive epidemiology, we compared suicide rates during the Spanish Flu period (1918–1920) to both the pre-pandemic period (1909–1917) and the post-pandemic period (1921–1929). We also compared New Zealand GDP levels during the same time-periods.⁸

Results

During the Spanish Flu pandemic (1918–1920), New Zealand crude suicide rates (Table 1) averaged 11.2 per 100,000 population and were 6.4% lower than suicide rates between 1909–1917 (12 per 100,000 population). Male and female suicide rates reduced by 4.5% and 5.8% respectively during this same comparison time-periods. When compared with the World War I period (1914–1918), suicide rates during the Spanish Flu period (1918–1920) were marginally lower, but there is an overlap in 1918. Notably, during the overlap year (1918), when disaster-related mortality due to a combination of the Spanish Flu (0.57% population mortality in 1918) and World War I (0.32% population mortality in 1918) was at its peak,⁵ the suicide rate of 10.2 per 100,000 population was the second-lowest documented between 1909 and 1929 (lowest was 10.1 per 100,000 population in 1910). In the post-pandemic period (1921–1929), suicide rates increased by 16.7%, compared with the Spanish Flu period (1918–1920), with male and female suicide rates increasing by 13.1% and 29.5% respectively.

The 6.4% reduction in New Zealand suicide rates during the Spanish Flu pandemic (1918–1920) compared with 1909–1917 was associated with an incremental rise in New Zealand GDP levels,⁸ which were 2% higher between 1918–1920 (average GDP US$7297) compared to 1909–1917 (average GDP US$7132). However, following the pandemic (1921–1929), the 16.7% increase in suicide rates compared to the Spanish Flu period was associated with a 4.1% decline in average GDP levels between 1921–1929 (average GDP US$6995).

Table 1: New Zealand crude suicide rates, Spanish Flu mortality, World War I mortality and GDP between 1909 and 1929.

Discussion

New Zealand suicide rates have appeared lower during the Spanish Flu pandemic and the early phase of the COVID-19 pandemic, a century later. Significantly, New Zealand suicide rates during the Spanish Flu pandemic have similarities with the reduced US suicide rates during the same pandemic.⁹ There may be sociological and economic reasons for reduced suicide rates during pandemics, despite the impact of public health measures on travel, family life and personal freedoms. Within a collective experience of a disaster, social cohesion may increase with an emerging sense of shared identity and solidarity.¹⁰ Such increased social cohesion and the relative stability of New Zealand GDP may explain the slight reduction in New Zealand suicide rates during the Spanish Flu. Durkheim first hypothesised great national crises, like wars, may protect against suicide because of an increased sense of patriotism and social connectedness leading to greater integration of society.¹¹ COVID-19 society-wide experiences and community pride in the successful public health measures might be inducing similar community-building sentiments in contemporary New Zealand.

Historical analysis of suicide rates during the Spanish Flu pandemic suggest that, because of the potential protective effect of social cohesion in the short-term, New Zealand’s suicide rates may not be greatly affected by COVID-19. The evidence to date shows that shared adversity, community-wide solidarity and possibly increased altruism may partially mitigate the effects of relative economic hardship on the population risk of suicide during the early phase of the COVID-19 pandemic in New Zealand. Importantly, New Zealand has experienced the lowest COVID-19 cumulative death rate in the OECD (as of 26 June 2021) and also had the lowest level of “excess deaths” among OECD countries.¹² New Zealand has also performed better than other OECD countries in terms of GDP maintenance and lower unemployment rate increases, so there is a better economic baseline.¹² However, a higher suicide-risk might occur after COVID-19 pandemic resolution in New Zealand, particularly if the economy stagnates and social cohesion is reduced.

We note some limitations with respect to data accuracy of New Zealand suicide mortality data between the years 1909 and 1929. However, ongoing epidemiological and economic research is needed to ascertain the short-, medium- and longer-term impacts of the COVID-19 pandemic on New Zealand and global suicide rates. This will help to inform evidence-based economic and social policy responses.