Mental health experts and officials are divided over a study from the Office of National Statistics, which has linked extreme heat with almost 700 suicides over a 22-year period.
There were 72 suicides in London associated with extreme heat from 2001 to 2023, and 695 in England and Wales overall.
The research was part of a new ONS initiative to assess the effect of climate change on health.
Professor Navneet Kapur, Professor of Psychiatry and Population Health at the University of Manchester, said: “Suicide is a complex phenomenon – there is no single cause.
“Researchers have been studying the link between temperature and suicide rates for a number of years and the majority of studies have reported a link.
“But the mechanisms by which heat increases suicide risk are speculative. No studies have demonstrated cause and effect.”
In London, 0.52% of suicides – around one in 200 – were related to high temperature.
This was lower than most other regions, such as Yorkshire and the Humber (0.92%), East Midlands (0.82%) and West Midlands (0.79%).
Interestingly, the South West had an inverse relationship with heat and saw five fewer deaths during hotter weather.
Male suicide prevention charity, James’ Place, reported that May, July and November were the periods where they received the highest number of referrals in London last year.
Its chief executive, Ellen O’Donoghue, said: “We know that some evidence suggests extreme weather can worsen suicidal thoughts in at-risk people. In general, studies show a consistent peak in suicide rates during spring and early summer.”
The deaths attributable to extreme heat occurred between June and September, with significant spikes in July and August.
Overall, there were 91 in June, 336 in July, 216 in August and 52 in September.
The three regions with the highest number of heat-related suicides were Yorkshire and the Humber (106), West Midlands (88) and the East of England (86).
London, which has the lowest suicide rate in the UK, had one of the fewest numbers attributable to heat (72).
Professor Kapur downplayed the role of heat in the geographical variation.
He said: “The main reason for some areas having higher suicide rates than others in the UK probably has much less to do with temperature and much more to do with socioeconomic drivers (such as unemployment) or clinical drivers (such as mental illness).”
Although ONS is a reliable source, a potential weakness in the data is that it is a modelled study, and that the attributable suicides are not individuals but are instead estimated on a population level.
While it is unclear exactly why suicide correlates with higher temperature, it is presumed that heat itself is not the cause, but how it interacts with other factors.
One possibility is that it exacerbates mental health issues such as depression and anxiety, which, in turn, can make people more impulsive.
Another factor could be that the use of alcohol and drugs, known risk factors for suicide, increases in hotter weather.
This study explained the effect of heat on physical and mental health.
It said: “Temperature may modulate symptoms of mental illness or worsen general mental health and wellbeing through a range of biological or cognitive and societal pathways.
“Higher or extreme temperatures can also disturb sleep and reduce its quality, which is known to increase mental health risk.”
Most regions in England and Wales saw an increase in the relative risk of suicide during higher temperatures, and this more than doubled in the North West, the North East and the East Midlands.
Nonetheless, mental health charity, Mind, was more concerned about the overarching impact of climate change rather than heat itself.
Its representative, Jess Childs, said: “Studies suggest a link between increasing temperatures and suicide, but less of a clear link between heatwaves and suicide.
“So we wouldn’t necessarily emphasise a link between extreme heat and suicide.”
She referenced Mind’s official guidance on climate change, which states: “Social inequality, climate change and health problems all overlap and reinforce each other. It is a vicious cycle.”
As temperatures are expected to increase through global warming, more extreme weather events are anticipated.
Professor Kapur acknowledged: “It is certainly something that should be of interest to policy makers as well as researchers.”
Accordingly, more analysis will be needed to both explain the link and mitigate the risk between heat and suicide.
Until then, unanimity in the sector seems unlikely.
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