Motivation and emotion/Book/2017/Temperature and mood

Temperature and mood:
What is the effect of temperature on mood?

Multimedia presentation (3 min)

Overview

"She is cold today". What comes into your mind when you hear or read this sentence? Normally, people arrive at two types of interpretations. First, it could be the person is feeling cold due to lower body temperature that is caused by an illness or the person is not in the mood to mingle with friends and is rather aloof and withdrawn. Whatever your inference, you can't go wrong because temperature and mood are correlated. This chapter focuses on the effect of temperature on mood, allowing us to understand our own mood through the lens of temperature dynamics.

Key goals of this chapter Define temperature and mood, and describe how they are associated to each other Explain the effect of temperature on mood Understand what we can do about it

Temperature and mood

When you exercise or are exposed to warm environments, your body temperature rises. This is because temperature is not constant. For humans, both our body and brain temperature are affected by what we do, what we eat and where we at. By the time our temperature changes, our mood changes too. After exercising a hot environment, we may feel particularly tired and irritated because temperature and mood are connected.

Human body temperature

The normal human body temperature is in the range of 36.5 to 37.5 °C. It is maintained within this range by a process called thermoregulation despite changes in the environment (Blatteis, 2001). However, this scale is sometimes not sustained by the body. Human body temperature varies during the day. A healthy person reaches the lowest level of body temperature at around 6 o’clock in the morning while the highest is at around 6 o’clock in the afternoon (Pusnik & Miklavec, 2009). However, this is not definitive as our body temperature is affected by many factors.

It is usually noticeable when our body increases or decreases its temperature. We may feel hot or cold, and this is due to several factors (Pusnik & Miklavec, 2009), including: 

• Infection
• Cancer diseases
• Allergic reactions
• Hormone disorders
• Autoimmune diseases
• Excessive physical activity, especially in a hot climate
• Excessive exposure to the sun
• Medicine intake
• Hypothalamus injury
• Nutrition, alcohol intake and smoking

Brain temperature

The average brain temperature of humans is less than 1°C higher than body temperature (Wang et al., 2014). Brain temperature homeostasis is determined by in-brain heat production and dissipation by cerebral flow. It is also affected by the person's metabolism and the efficiency of heat dissipation to the external environment via skin and lung surfaces (Kiyatkin, 2007). However, just like body temperature, brain temperature is affected by physical activity and the external environment. Increased physical activity could increase core body temperature which then increases brain temperature (Nybo, 2012). Similarly, hot and humid conditions result in progressive accumulation of heat in the body and brain (Kiyatkin, 2007). It is, therefore, hypothesised that environmental challenges are a major cause of brain and body temperature fluctuations (Kiyatkin, 2010).

These changes in the temperature of the brain could affect several neural process and functions (Kiyatkin, 2010; Kiyatkin, 2007). Synaptic transmission is temperature-dependent (Katz & Miledi, 1965). Thus brain functions are altered by brain temperature. This shows an empirical evidence of the relationship of brain temperature and brain activity and function.

Mood

Mood is significantly associated with brain temperature. Lithium, some neuroleptics and single Electroconvulsive therapy (ECT), for instance, reduce brain temperature and at the same time reduce mania. While chronic administration of antidepressant medications and long term ECT tend to produce heat, eventually improving depression (Salerian, Salerian, & Saleri, 2008).

But what exactly is mood? When we say that the weather makes us depressed we are saying that we are in a depressed mood. That is, the world looks grey and uninteresting rather than saying that you are sad about a particular event.  It is because mood does not have specific intentional object as it is about everything in general unlike emotion. Being sad about someone's death is showing the emotion of sadness while saying that reading old letters makes you sad means it is causing you sad mood (Wong, 2016; Sizer, 2000). Therefore, mood is more general while emotion is more specific. Being a functional state that affects how we represent the world, moods are able to facilitate different thoughts, judgments, or emotions by affecting different faculties of our functional architecture such as judgments, processing styles, memories, and creativity (Wong, 2016).  

Mood is a mental state that monitors our bodily condition. According to Morris (2000), there is some evidence that normal and disordered moods are affected by biological processes that are related to energy such as exercise, food intake, illness processes, circadian rhythms, and brain and body temperature fluctuations. Therefore, mood, similar to human body temperature and brain temperature, is a variable that is highly influenced by both biological processes and the physical environment.

Does seasonal change affect our mood?

Figure 1. The girl's mood is just as perfect as the weather.

There is a belief that weather or season is associated with mood. According to Yang (1997), there are clear relations between affective disorder and seasonal change. But there is also evidence that there are no consistent effects of weather on mood (Ciucci et al., 2011; Denissen et al., 2008; Keller et al., 2005). The presence or absence of sunlight determines the weather's temperature (Denissen, Butalid, Penke & van Akenm 2008) which gradually increases body's temperature (Pusnik & Miklavec 2009). Yet, the impact also seems to vary between days and seasons due to the activities that one performs. Despite some contradictory results, the following trends are evident.

Summer heat

• Spending more time outside during summer days can result in decreased mood (Kelly et al., 2005).
• Sunlight has a significant effect on tiredness (Denissen et al., 2008).
• Mania attack is high (Yang, 1997)

Cold winter

• Sunny winter days make children more cheerful (Ciucci et al., 2011).
• Depression mostly occurs during winter (Rosenthal et al., 1984)
• Depressive attack is high from autumn to winter (Yang, 1997).

Spring days

• On spring days, when people stays outside for a long time, mood was found to be positively associated with air temperature (Kelly et al., 2005).
• Mania attack is high, too, just like during the summer (Yang, 1997).

The rising temperature of the world

"All around the world across different societies in the modern world as well as throughout history, we find that human conflict seems to be linked to changes in climate," says Hsiang, Burke and Miguel (2013).

Figure 3. Global temperature anomaly, difference from the average or normal temperature

Drawing from archaeology, criminology, economics, geography, history, political science, and psychology, the authors assemble and analyse the 60 most rigorous quantitative studies and document about influence of climate on human conflict, for the first time, a striking convergence of results (Hsiang et al., 2013).

Three of the distinct qualities of climate change are rising temperature, drought and heavy rainfall. But rising temperature, especially, has the greatest effect on human conflict. The equivalent of a five degree Fahrenheit increase in an average USA county over a month could raise the odds of personal violence such as assault, murder and domestic violence by 4%, and the risk of civil war, riots or ethnic violence by 14% (Hsiang et al., 2013). The result of the study showed that the relationship between climate change and conflict is both substantial and highly statistically significant. Thus, warmer temperatures or extremes of rainfall can be causally associated with increases in interpersonal violence and civil war.

With the rising temperature known to be a factor of conflict, it is not a surprise as to why studies such as Wei and Cau (2005) and Holland et al. (1985) concluded high temperature to cause irritability and aggressiveness. These two types of mood reinforce violence and conflict.

Activity I - Let's rehearse

Match the image with its corresponding word/s. Write the letter of your answer in the box, once completed, click 'Submit'. (All 3 pictures are equivalent to 1 point, so make sure to match up all pictures and words correctly.)

A. moods

B. sadness

C. increased body temperature

Temperature on mood

Research in psychology has shown that temperature affects mood significantly (Cao & Wei, 2005; Holland, Sayers, Keatinge, Davis, & Peswani, 1985). Thus, attracting massive attention for further investigation which led to some important knowledge about the influence of temperature towards mood. These studies include the work of Holland et al. (1985), Cao and Wei (2005) and Bullock, Murray and Meyer (2017). Holland et al.(1985) conducted an experiment that had immersed subjects (volunteers) into 41°C water, increasing their core body temperature to 38.80 - 39.05°C. Volunteers reported that they found a significant decrease in alertness and increase in irritability. The authors concluded that temperature has an effect on mood.

Cao and Wei (2005) investigated whether stock market returns are related to temperature, they have scientifically proven that temperature has an impact on mood. The study suggests that lower temperature can lead to aggression. This explains the higher stock returns during the time that the temperature is low. But when the temperature is high, apathy and aggression correlates to lower and higher stock returns. Although mostly, apathy dominates aggression when it is cold. This mood changes, influenced by the temperature, result to how people behave in the stock market. The result of the two experiments (Cao & Wei, 2005; Holland et al.,1985) support each other.

The set of information specifying the effect of temperature on mood is truly convincing given the scientific and empirical evidences. However, when we talk about evidence, there is another study that proves that mood is influences changes in body temperature, contrary to the hypothesis that temperature affects mood. In a series of five experiments, it was found that emotional feelings are associated with discrete, yet partially overlapping maps of bodily sensations, which could be at the core of the emotional experience (Nummenmaa, Glerean, Hari & Hietanen 2014). Different emotions were consistently associated with statistically separable bodily sensation maps. These bodily sensations could either make temperature of specific body regions go up or down due to changes in physiological activities caused by different emotions. Does this study prove the phrase "hot under the collar" and "hot headed" to be physiologically accurate?

Table 1.

This chart shows the body region temperature which increased (red shade) or decreased (blue shade) when feeling each emotion according to Nummenmaa et al. (2014).

Emotions	head	throat	chest	shoulder	upper limbs	abdomen	hip	lower limbs
Anger
fear
disgust
Happiness
sadness
surprise
Anxiety
love
depression
contempt
pride
shame
envy

But a recent study by Bullock, Murray and Meyer (2017) further supported the effect of temperature on mood (Cao & Wei, 2005; Holland et al.,1985). They examined meteorological factors, such as atmospheric pressure, hours of sunshine, relative humidity, and daily maximum and minimum temperatures as more proximal predictors of self-reported daily mood change in people diagnosed with bipolar disorder. The results showed that daily maximum temperature was the only meteorological variable to predict clinically-relevant mood change, with increases in temperature associated with greater odds of a transition into manic mood states. Hence, instead of saying that the weather affects our mood, it is more accurate to say, the temperature which is a fragment of weather influence our mood.

The effect of temperature on mood can be explained further by looking through the perspectives of biological and evolutionary psychology.

Biological perspective

There is a fundamental understanding of temperature dynamics in the brain and the interactions between temperature, cerebral blood flow (CBF), regional brain activity and neuronal viability (Wang et al, 2014). In fact, it has been reported that cerebral functional activities are temperature-dependent and brain temperature alone may act as an active and dynamic factor with the capacity to regulate brain activity and function. For example, 70% of information that is normally retained during memory encoding is lost at approximately 34-35°C body temperature. In addition, synaptic transmission is also proven to be temperature-dependent (Katz & Miledi, 1965). More importantly, some biogenic amines are directly involved in thermoregulation (Jonc & Murphy, 1993). During temperature fluctuations,  production of neurotransmitters and hormones like serotonin and melatonin in the body is altered (Abbas, Khan & Helaluddin, 2011). Hence, changes in brain temperature influence the mental states of a person (Jonc & Murphy, 1993). It suggests the interaction between temperature, brain activities and emotional-related neurotransmitters and hormones.

Serotonin

Figure 2. Serotonin neurotransmitter that regulates mood.

According to Abbas et al. (2011), the effect of photoperiod and temperature can alter the production of serotonin in body. Serotonin is a neurotransmitter released in the brain and gastrointestinal tract. It regulates functions in the body such as mood, sleep, appetite, temperature regulation, perception of pain regulation of blood pressure and vomiting. Serotonin is implicated with depression (Abbas et al., 2011), which is characterised with sad moods caused by low serotonin levels. Selective serotonin reuptake inhibitors (SSRI) are a class of drugs used to treat depression. They aim to increase the availability of the neurotransmitter Serotonin. 

According to Abbas et al. (2011), mood can be seasonal according to temperature and season we experience. Depression increases as temperature decreases and serotonin plays a vital role. Exposure to sun increases human body temperature (Pusnik & Miklavec, 2009; Denissen et al., 2008) and brain temperature (Kiyatkin, 2007). Thus, the lack thereof means the tendency of a decreased temperature of both body and brain. This could significantly affect how brain functions. During winter, people experience short days and long nights with extreme cold temperature. This is the time of the year when the turnover of serotonin in our body is the lowest and the feeling of being depressed increases. This proves the idea that the production of serotonin that is affecting people's mood was directly related to duration of sunlight and temperature. Furthermore, there is an emerging evidence that serotonin functions in positive affective responses to warm temperature (Raison et al., 2014). This implies that serotonin plays a significant role in the relationship between temperature and moods.

Thermoregulation and thermosensation processes

Thermoregulatory and thermosensory processes meaningfully contribute to the affective experiences of humans (Raison et al., 2014). Depressed patients have high core body temperature but do not sweat. It may be because they experience irregular thermoregulation processes. According to the study, flawed thermoregulation contributes to depression. This shows that the relationship between physical temperature and affect. The team discovered that the neural pathway of thermoregulation and depression is the same. This explains the reason regarding the increased activation of the region of the brain that is related to emotional processing during warm stimulation (Sung et al., 2007).

Information about skin temperature reaches the brain through specific pathways. For patients with mood disorders, their brain regions that is involved with registering and reacting to thermal signals has been found to function abnormally. It is therefore concluded that dysregulation of thermosensory pathways is associated with affective disorder (Raison et al., 2014). 

Williams and Bargh (1998) found that when a person is exposed to a physically warm object, he/she tends to be warm in their perception too because exposure to physically warm stimuli tends to activate the concept of "warmth" in working memory. It simply activates linked concepts, feelings, and action tendencies. When such information is active in working memory, it is likely to shape people's judgments, feelings, and behaviours (Raison et al., 2014).

Thus, Raison et al. (2014) put forward three main arguments. First, thermosensory pathways interact with brain systems that control affective function, second, these pathways are dysregulated in affective disorders, and third, activating warm thermosensory pathways promotes a sense of well-being and has therapeutic potential in the treatment of affective disorders.

Evolutionary perspectives

There is a consensus that affect, emotion and mood were shaped by natural selection. Mood, for example, resulted from situations that either offer opportunity or threat (Nesse & Ellsworth, 2009). Thus, increased, decreased or normal temperature lead to changes in mood . It is our way of adapting to the environment in order for us to survive and reproduce. For example, aggressiveness is assumed to be a solution to defending against attacks and negotiating power and status hierarchies amid conflict (Buss & Shackelford, 1997). Further, low mood, in particular, is most generally associated with loss (Nesse & Ellsworth, 2009). It can be about temperature and sunlight knowing that decreased temperature and low exposure to sunlight could result to low mood. Low mood arises when desires cannot be satisfied (Nesse & Ellsworth, 2009). These desires could include normal temperature and opportunity to perform activities outside. Thus, due to low temperature on winter days, people would feel more sad throughout the day, preventing them to stay outside for a long time and from acquiring hypothermia. The adaptive function of mood is to integrate information about the recent state of the environment and current physical condition of the organism to fine-tune its decisions about the allocation of behavioural effort (Nettle & Bateson, 2012). Furthermore, there is a strong evidence that the capacity for mood is an adaptation to other less tangible stimuli (Nesse & Ellsworth, 2009), such as sunlight and wind.

Evolutionary views on the effect of temperature on mood state that some clinical depression arises from abnormal brain mechanisms, and most arises from interactions of brain variations with environ­mental situations (Nesse & Ellsworth, 2009). This hypothesis is parallel to that of biological perspective.

Activity II - Let's rehearse

Here are some quiz questions - choose the correct answers and click "Submit":

1 If a person is immersed in warm water, what mood would that person be typically in?

	increased annoyance and sadness
	decreased alertness and increased irritability
	frustrated and mad
	increased restlessness and irritability
	decreased sadness and and decreases alertness

2 Which statement best describes a person with flawed thermoregulation according to Raison et al. (2014).

	Depressed patients have high core body temperature but do not sweat
	Persons with elevated mood have low core body temperature and do not sweat
	Depressed patients have high core body temperature and sweat a lot.
	Depressed patients have low core body temperature and do not sweat.
	Patients with elevated mood have high core body temperature but do not sweat.

What can we do?

Temperature is scientifically proven to have a significant effect on mood. Thus, as a human being, we could maintain a positive mood through different ways. First, it is important to ensure that our core body temperature is within normal range. Activities that are physical and expose you to sun must not be overdone as it could increase body temperature rapidly. While infections, diseases, allergic reactions and medicinal intake must be closely monitored as it could result to conditions like hyperthermia and hypothermia.

Second, despite heterogenous results of the investigation about the relationship between weather and mood, it is still empirical to protect ourselves from bad weather (Denissen, Butalid, Penke, & Van Aken, 2008). Temperature, as one of the most important component of weather, along with humidity and sunlight, were found to directly affect our mood. Thus, during cold days, it is important to wear clothing such as jackets, hats, gloves, boots and others, enough to make yourself warm to avoid having low mood. In contrast, in summer season, light clothing is recommended. Cotton-made clothes, sleeveless shirts and shorts are helpful to keep your body fresh and cool under the scorching sun.

For long-term interventions, it is recommended to formulate plans to help prevent climate change. Following the proposition of Hsiang et al. (2013), climate change is linked to conflict. This is especially in relation to the rising of temperature. Policy support and risk perception over climate change are strongly influenced by experiential factors, including affect, imagery, and values (Leiserowitz, 2006). Therefore, it will be beneficial to provide awareness to all people and this could begin at homes and schools. This will help create a better understanding of social responsibility at individual and community level.

Conclusion

• Temperature and mood are associated with each other and are affected by bodily responses and environmental challenges.
• Weather is not directly associated with mood. However, temperature, a fundamental feature of weather, is proven to affect mood. An increase in temperature can cause aggressiveness and irritability while a decrease in temperature leads to depression or low moods.
• Mood is our response to our bodily condition and adaptation that is challenged by temperature.
• There are certain measures that we can perform to sustain positive mood.

See also

• Season and emotion (Book chapter, 2015))
• Human body temperature (Wikipedia)
• Mood (psychology) (Wikipedia)

References

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External links

• Can weather affect your mood? (psychcentral.com)
• Turn up the heat to turn down depression? (uanews.arizona.edu)
• Why you're sad in the winter? (youtube.com)
• Feeling hot can fuel rage (scientificamerican.com)