There is a link between heat and mental health; and climate change is making it more pronounced

There has been an increase in footfall at major psychiatric hospitals in the country since March, an unusually hot month this year

By Taran Deol
Published: Monday 25 April 2022
A hot day in Old Delhi. Photo: iStock
A hot day in Old Delhi. Photo: iStock A hot day in Old Delhi. Photo: iStock

March 2022 was the hottest month the India Meteorological Department (IMD) has recorded in the 122 years since the agency began the exercise. The impact of this on mental health cases was noticeable at the Central Institute of Psychiatry (CIP) in Ranchi.

The CIP recorded a 10-20 per cent increase in footfall, a trend that usually begins in April and lasts till June-end. Cases of bipolar disorder in the manic stage were the most common cause of hospitalisation in March this year.

For this, excitement, irritability and aggression are some of the common symptoms. Substance abuse, including cannabis and alcohol, is another key reason.

“Significant gaps exist in our understanding of the impact of heat on mental health. One standard deviation of temperature increase leads to a four per cent increase in interpersonal violence and 14 per cent increase in group violence. High risk behaviours also increase during heat waves,” Dr Basudeb Das, director at CIP Ranchi, told Down To Earth.

“Evidence has shown that having a pre-existing psychiatric illness can triple the risk of death during a heat wave. Children and the elderly are at a risk of dehydration and electrolyte imbalance which can cause behavioural symptoms,” he added.

Jharkhand has recorded 11 heatwave days this year. According to the IMD, a heatwave in the plains means temperatures higher than 40 degrees Celsius, while a heatwave in the coastal and hilly areas is when temperatures cross 37 and 30°C respectively.

If the temperature of a region is 4.5 to 6.4°C higher than normal, it is termed a ‘heatwave’ and if it is greater than 6.4°C, it is termed a severe ‘heatwave’.

The impact of higher temperatures on mental health is not always this direct. Lithium is a mood stabilising agent largely administered in bipolar patients. It increases sweating and the body demands high intake of water.

“This can go two ways. On one hand, higher temperatures cause dehydration in patients on lithium, increasing the probability of lithium toxicity.

“On the other hand, there are chances the patient will stop taking the medication — given the increase in the body’s heat production — and relapse,” Dr Om Prakash, professor of psychiatry at Institute of Human Behaviour and Allied Sciences (IHBAS), New Delhi, told DTE.

Patients of mania, acute psychosis and bipolar relapse account for an estimated 20 per cent of the roughly 1,800-2,000 patients currently being treated daily at IHBAS.

At Ram Manohar Lohia Hospital in the capital, cases of bipolar disorder in the manic phase increase by around 5-10 per cent in May and June, according to Dr Ram Prasad Benival.

He is professor of psychiatry at the Center of Excellence in Mental Health, Atal Bihari Vajpayee Institute of Medical Sciences & Dr RML Hospital, New Delhi. The national capital region has recorded 15 heatwave days this year.

Similar trends are being recorded at Sardar Patel Medical College in Bikaner, Rajasthan.

According to assistant professor of psychiatry Rakesh Gharwal, cases of bipolar disorder in the manic phase increased by 5-10 per cent starting this month. It is a trend that’s likely to continue till June-end.

However, cases of bipolar relapse are higher, witnessing a 30-40 per cent increase in the hotter months of the year. Those on antipsychotics are also prone to being hospitalised, although this is rare.

“High perspiration in summers can cause a change in metabolism. This can sometimes result in neuroleptic malignant syndrome — a life-threatening psychiatric emergency condition occurring mostly in the younger population.

“This is largely caused by high perspiration and improper hydration resulting in a higher drug concentration,” Gharwal explained.

Rajasthan and Madhya Pradesh have recorded the maximum number of heatwave days this year, at 25 each. They are followed by Himachal Pradesh at 21, Gujarat at 19 and Jammu and Kashmir at 16.

The Intergovernmental Panel on Climate Change assessment report released in March 2022 notes the direct and indirect effects of climate exposure on mental health.

These range from extreme weather events or prolonged high temperatures as direct causes and undernutrition or displacement as indirect.

The report cited a study conducted in the United States. It “found mental health problems increased by 0.5 per cent when average temperatures exceeded 30°C, compared to averages between 25-30°C; a 1°C warming over five years was associated with a two per cent increase in mental health problems.”

Similar findings were reported from another study where a “1°C rise in monthly average temperatures over several decades was associated with a 2.1 per cent rise in suicide rates in Mexico and a 0.7 per cent rise in suicide rates in the US.”

According to the report, heat-related mental health outcomes include suicide, psychiatric hospital admissions and ER visits for mental disorder, experiences of anxiety, depression, and acute stress.

An August 2021 meta-analysis of 53 high temperatures / heatwaves studies published between January 1990 and November 2020, covered more than 1.7 million mental health-related mortality and 1.9 million morbidity cases.

It found a 2.2 per cent increase in mental health-related mortality and a 0.9 per cent increase in mental health-related morbidity with every 1°C rise in temperature.

“In the context of global warming, it would be useful for local health authorities and service providers to incorporate mental health impacts into their heatwave warning systems, and to have public health policies and guidelines addressing preventable heat-related mental health mortality and morbidity,” the study, published in Science Direct, noted.

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