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How Weather Influences the Brain?

We all know that the weather can strongly influence our mood and productivity. Many people feel better when the weather is nice and sunny. It is thus not surprising that people more often feel unhappy and depressed in winter. There is even a medical condition known as winter depression. Still, some researchers believe that our brain functions better during the cold days. In this article, I’ll briefly analyze what happens in our brain in relation to weather-related mood and mind changes.

Scientific studies indicate that weather conditions such as high temperature and humidity can impair mental performance by affecting brain neurochemistry. For instance, it is believed that thermal stress can cause cognitive impairment.

One recent study has investigated the impact of thermal stress on cognitive functions in soldiers spending at least one year in desert conditions. The evaluation of memory and cognitive functions indicated there is a decline in cognitive performance in hot climates when compared to normal weather. The decline was most pronounced for attention, concentration, verbal memory, and psychomotor performance.

Another recent study has investigated the impact of sand and dust storms on children’s cognitive function. Using mathematical analysis and word-recognition test scores, how prenatal exposure to sand and dust storms affects the cognitive performance of children was evaluated. The authors found a decline in both test scores, as well as a later beginning of counting and speaking in whole sentences in children prenatally exposed to storms. The findings imply that this kind of weather jeopardizes the cognitive functions of the next generation.

However, results from scientific research on the effects of temperature on cognitive functions are quite mixed and contradictory.

One study investigated how temperature affects the cognitive performance of subjects with multiple sclerosis. Healthy subjects were included as controls. The researchers correlated cognitive status with temperature in both study groups. In patients with multiple sclerosis, unlike in healthy subjects, the higher temperatures were associated with worsening cognitive status. These findings confirmed that warmer outdoor temperatures lead to a higher incidence of clinical exacerbation and T2 lesion activity in subjects with this condition (T2 lesions represent the white spots observed by MRI that are used to diagnose and track the progress of multiple sclerosis).

With regard to cognitive functions in cold weather, studies have shown both impairments and improvements.

For instance, one study investigated the impact of exposure to the cold and the following rewarming on working memory and executive functions in 10 young males. The results demonstrated a decline in the test results when the subjects were exposed to 10°C, and these impairments persisted for one hour during the rewarming period. Although the underlying mechanisms were not tested, the authors suggested that acute vascular changes in the brain could explain the observed changes. According to the authors, another explanation could be a deregulation of catecholamine levels, particularly important for complex attentional functions.

Other findings suggest that winter helps to wake up our mind and makes us think more clearly. It is well known that the brain utilizes glucose as its main energy source. Thus, when glucose is depleted, brain functioning is jeopardized. Energy, i.e., glucose, is also used for the regulation of body temperature, especially in extremely hot or cold conditions. It seems that more energy (glucose) is needed to cool down than to warm up the body. Thus, warm temperatures are more likely to deplete glucose levels and thus impair brain function and clarity of thinking.

It has been suggested that high temperatures increase the risk of mental disorders, especially in the elderly.

One recent study has analyzed data on emergency admissions linked to mental diseases and daily temperatures over a period of more than 10 years in 6 different cities. The results indicated that high temperatures might jeopardize mental health and be responsible for the exacerbation of symptoms of mental diseases. For instance, according to the results, more than 30% of admissions for anxiety were attributed to hot temperatures. Exposure to hot temperatures leads to reactions in the body that may cause an increase in stress hormone levels and brain temperature. Additionally, extremely hot weather may deregulate the dopamine and serotonin levels (these neuromediators are important for the feeling of happiness).

According to widespread belief, weather can affect our mood. Although a lack of sunshine is commonly linked to seasonal depression, some researchers believe that not all individuals respond similarly to weather changes.

Research has linked an individual’s self-reported daily mood with the objective weather over a 30 day period. Large individual differences have been found in how people react to the weather. Accordingly, four distinct types of weather responders have been identified: summer lovers (i.e., a better mood with warmer weather and more sun), summer haters (i.e., a worse mood with warmer weather and more sun), rain haters (i.e., a bad mood on rainy days), and unaffected (i.e., no particular association between weather and mood). Interestingly, adolescents and their mothers are often the same type, suggestive of familial weather reactivity.

The analysis of both scientific and popular literature permits the conclusion that extreme weather conditions can affect our cognitive function and mood. Most likely, this is caused by a decline in the brain’s energy source (glucose), which needs to be used for thermoregulation. Also, it is evident that extreme temperatures affect the level of catecholamines in the brain (such as dopamine and serotonin). Still, it seems that there is some individual variability in the brain’s response to weather, and it may run in the family.

References

Saini, R., Srivastava, K., Agrawal, S., Das, R. C. (2017) Cognitive deficits due to thermal stress: An exploratory study on soldiers in deserts. Med Journal Armed Forces India. 73(4):370-374. doi: 10.1016/j.mjafi.2017.07.011.

Li, Z., Chen, L., Li, M., Cohen, J. (2018) Prenatal exposure to sand and dust storms and children’s cognitive function in China: a quasi-experimental study. The Lancet. Planetary Health. 2(5): e214-e222. doi: 10.1016/S2542-5196(18)30068-8.

Leavitt, V.M., Sumowski, J.F., Chiaravalloti, N., Deluca, J. (2012) Warmer outdoor temperature is associated with worse cognitive status in multiple sclerosis. Neurology. 78(13): 964-968. doi: 10.1212/WNL.0b013e31824d5834.

Muller, M.D., Gunstad, J., Alosco, M.L., Miller, L.A., Updegraff, J., Spitznagel, M.B., Glickman, E,L. (2012) Acute cold exposure and cognitive function: evidence for sustained impairment. Ergonomics. 55(7): 792-798. doi: 10.1080/00140139.2012.665497.

Lee, S., Lee, H., Myung, W., Kim, E.J., Kim, H. (2018) Mental disease-related emergency admissions attributable to hot temperatures. The Science of Total Environment.616-617: 688-694. doi: 10.1016/j.scitotenv.2017.10.260.

Klimstra, T.A., Frijns, T., Keijsers, L., et al. (2011) Come rain or come shine: individual differences in how weather affects mood. Emotion. 11(6): 1495-1499. doi: 10.1037/a0024649.

Image via geralt/Pixabay.


Source: Brain Blogger

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