What does the weather have to do with anything?
Weather. A hackneyed conversation starter, that creeps into awkward silences and everyday insouciant banter. Despite the spotlight it already enjoys, weather continues to be a subject of overt concern for many; its mercurial nature drawing in hosts who take their bets and anxiously wait. Weather, in all its glorious four seasons, has hence forever intrigued, and often eluded experts, who have tried to pin down weather patterns and trends, in order to better understand the global climate change struggle. Recently, however, there is another field of research associated with this star small-talk subject, the results of which are quickly gaining popularity on our social media feeds. Ever heard of winter blues?
Well contrary to what one might expect, winter blues are not as deadly as the summer or spring blues. For decades, scientists have researched and found that is actually the warmer season of summer or spring that serves as a factor associated with suicide and suicide attempts. This seems counterintuitive, doesn’t it? The dreary cold December with its retracted sunshine hours would make for a fitting narrative. Scientists Annie Hauser and Grady Dixon among others however disagree and note that:
“Spring is when severely depressed people are able to be motivated enough to take action and do something. In most people, depression creates overwhelming feelings of listlessness and disinterest, so the idea of putting together a plan to commit suicide is too difficult during the winter, when depression symptoms may be worse in some people. [Patients] know how they’re affected by seasonal winter depression. They anticipate they’ll feel better when spring and summer roll around. When they don’t, that’s a catalyst for suicide. One of the oldest theories holds that people who are depressed and withdrawn during the winter don’t bounce back in spring, like many of other people do 1”.
What is the current scientific research on the topic?
In the past, other hypotheses by scientists have tried to link increasing inflammation in the spring season (due to colds and allergies) to high suicide rate. These theories rest on biophysical impacts of inflammation and heart (amongst other fatal) diseases and culminate in correlating inflammation with suicidal and depressive thoughts 1.
Despite these and many other theories floating around, for years, however, isolating the role of temperature from other more dominant risk factors has been challenging. The US Centers for Disease Control and Prevention 2 (CDC) identifies “a combination of individual, relationship, community, and societal factors (to) contribute to the risk of suicide.” According to CDC, these factors include a family history of suicide or mistreatment, previous suicide attempts, mental illness, alcohol or substance abuse, aggressive or impulsive tendencies, religious or cultural beliefs, feeling isolated, loss, illness, barriers to mental health treatment, and the stigma associated with perceptions of mental health 2. Researchers have noted that race, discrimination and other social disparities may also amplify the risk of suicide.
But weather and suicide discussions have captivated researchers for centuries, and although we are only recently seeing scientific studies published on the topic, it is a finding recognized for eons that suicides are more likely to peak during warmer months.
Back in 2018, Stanford economist Marshall Burke published his team’s findings in Nature Climate Change 3. According to the results of their study, projected temperature increases through 2050 could lead to an additional 21,000 suicides in the United States and Mexico. In an attempt to find a correlation between temperature and suicidal behavior, Burke’s team analyzed past temperature and suicide data across thousands of U.S. counties and Mexican municipalities over the period of several decades. The team also examined the language in over half a billion Twitter updates or tweets to investigate whether hotter temperatures affect mental health 4.
The results confirmed their hypotheses as the team found compelling evidence that hotter weather increases suicide rates. The team also found the use of depressive language such as “lonely,” “trapped” or “suicidal” in social media tweets more often during hot spells than during colder months. Burke noted that these effects differ very little based on how rich populations are or if they are used to warm weather 5.
After taking into account population growth and no less than 30 climate models, the team also found that if the world warms by 2.5 degrees Celsius by 2050, it could result in a 1.4 percent increase in America’s suicide rate and a 2.3 percent increase in Mexico’s suicide rate. To put things in perspective, Burke’s team found the effects of temperature on suicide to be roughly as large in size as the influence of economic recessions (which increase the rate) or suicide prevention programs and gun restriction laws (which decrease the rate) 4.
“We’ve been studying the effects of warming on conflict and violence for years, finding that people fight more when it’s hot. Now we see that in addition to hurting others, some individuals hurt themselves. It appears that heat profoundly affects the human mind and how we decide to inflict harm,” said Professor Solomon Hsiang, who co-authored the study 4.
A short history of scientific research on weather and suicide rates
This 2018 study confirmed much of the findings published in previous years related to weather’s potential effects on a person’s mindset. A paper in the 2014 edition of International Journal of Environmental Research and Public Health titled “Association of Weekly Suicide Rates with Temperature Anomalies in Two Different Climate Types” explored weekly suicide death totals and inconsistencies from Toronto, Canada, and Jackson, USA 1. Scientists working for the study found, that for both cities cooler weeks showed a lower probability of experiencing high-end suicide totals. Warmer weeks had an increased likelihood of being associated with high-end suicide totals. The study, led by Grady Dixon published the following findings:
“Weekly suicide totals demonstrate a sufficient association with temperature anomalies to allow some prediction of weeks with or without increased suicide frequency. While this finding alone is unlikely to have immediate clinical implications, these results are an important step toward clarifying the biopsychosocial mechanisms of suicidal behavior through a more nuanced understanding of the relationship between temperature and suicide 1”.
We find many other instances of such linkages made when we analyze past academic literature closely 6 7. A 2007 study in The American Journal of Epidemiology referred to a minor association between weather and suicide but questioned the significance of the association. More recent findings, however, have delved deeper and found evidence to support past claims. A 2017 paper in the Proceedings of the National Academy of Sciences emphasized on the increased suicide rates in India and linked that to crop-damaging temperatures. A 2016 study in Environmental Health Perspectives reported consistent positive associations between warmer temperatures and suicide in 3 East Asian countries, irrespective of country, age and gender 1.
Dixon along with his co-scientist colleague Adam Kalkstein has recently published a follow-up research piece to their 2014 study with a 2018 study in The International Journal of Biometeorology. In that study, they examine 9 major cities in the US to find those above average temperatures were associated with increased suicide risk in all counties and that there was a tendency towards late spring/summer peaks 1.
Apart from studying just temperature as a weather-related factor associated with suicide, research has also been conducted to examine other factors linked to suicide such as the duration of sunlight and seasonality. Even though a 2017 study in Progress in Neuro-Psychopharmacology and Biological Psychiatry backed up the hypothesis that sunshine has an increasing effect on the risk of suicide, the authors were still left unconvinced about the significance of such effects, noting that the co-relations found were “prompt” and “weak 1.”
A 2016 study in The Journal of Affective Disorders entitled, “Do suicide attempts occur more frequently in the spring too? A systematic review and rhythmic analysis.” analyzed 29 science articles from 16 countries to study a variety of seasonal patterns. The results found suicide attempts to be most frequent in spring and summer. This result ties back both to the findings of as early as the 1800s as well as to the Dixon and Kalkstein’s 2018 study of 9 U.S. cities 1.
Can we truly trust the data?
While presenting a strong correlation between warm weather and increased suicides, the lead authors of the 2018 study in Nature, Dr. Burke, underscored that the rising temperature and climate change should not be viewed as direct contributors to suicide. The team concluded their findings by noting that “Temperature and climate may increase the risk of suicide by affecting the likelihood that an individual situation leads to an attempt at self-harm. Hotter temperatures are clearly not the only, nor the most important, risk factor for suicide, But our findings suggest that warming can have a surprisingly large impact on suicide risk, and this matters for both our understanding of mental health as well as for what we should expect as temperatures continue to warm 4”.
So despite evidence of suicides peaking in warmer months, it is still important to delve deeper and question all theories liking weather and suicide rates. Suicide is a complex and highly nuanced subject and there are many factors contributing to suicide that also vary seasonally – such as unemployment rates or the amount of daylight.
Burke maintains that even though climate change might seem like an abstract idea, the countless lives that are at risk because of unmitigated climate change are not mere numbers as they signify losses of family members across the nation. Burke goes further to note that “Suicide is one of the leading causes of death globally, and suicide rates in the U.S. have risen dramatically over the last 15 years. So better understanding the causes of suicide is a public health priority 4”.
