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Course:EOSC311/2025/The Psychological Effects of Daylight Cycles Based on Geographical Location

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Overview

Various psychological effects have been discussed to affect individuals living within unique geographical locations. Depending on the latitudes of these varying locations, the effects can differ. Some geographical locations at more extreme latitudes can experience unique geographical phenomena, such as Polar Night and Midnight Sun (also referred to as Polar Day). These can affect daylight cycles, resulting in psychological changes that are both mental and physical. Research done on this topic and the effects of these geographical changes have been inconclusive however, as various research results have contradicted each other. This wiki page will discuss the proposed psychological effects accompanied by experiencing these geographical phenomena and the potential psychological effects that latitude have on both mental and physical health.

Statement of connection and why you chose it

Initially, bridging the gap between Geology and Psychology was a large one, as Geology is a discipline that has major focuses on the study of the Earth and its processes. Psychology on the other hand, was one that primarily focused on the behaviour of an individual as well as the processes of their mind. Combining the two disciplines led to ideas on the effects of certain geographical locations and what effects it may have on the mind. It has been proven before that there are certain phenomena that can induce negative effects on the mind, however there may be some merit that these effects can turn out to be positive as well. Having these connections be analyzed can be helpful in discovering the effects of our environment on our overall health. By analyzing the research and exploring some of the contradictions that come from the results of various research journals on this topic, it could help to further solidify some connections between these Earth Sciences and Psychology.

Circles of Latitude

Figure 1. Circles of Latitude, including the Arctic Circle, Tropic of Cancer, Equator, Tropic of Capricorn, and Antarctic Circle.

The circles of latitude are horizontal lines that circle around the Earth that categorize specific latitudes into various circles. Depending on which circle you are situated in, you will experience different weather conditions and geographical phenomena. The circle that will be discussed the most is the Arctic Circle, which begins at 66°33'N, while the Antarctic Circle sits opposite, at 66°33'S. At the center is the Equator, at 0° (Figure 1)[1]. To compare the geographical effects of these latitudes, certain countries that sit close to these latitudes will be compared in order to determine the differences in psychological effects.


These more extreme latitudes can result in distinctive geographical phenomena, such as polar night and midnight sun, which are seasonal phenomena. Seasonal changes tend to be more extreme within the Arctic and Antarctic latitudes compared to equatorial regions, with higher latitudes resulting in higher variability of duration in sunlight[2]. These latitudinal variations have been hypothesized to cause various psychological effects, such as causing mental distress and variations of sleep loss, and even insomnia.

Polar Night and Midnight Sun (Polar Day)

Polar night and midnight sun (also known as polar day), are geographical phenomena that happen seasonally during winter and summer months in both north of the Arctic Circle and south of the Antarctic Circle. The polar night is characterized as a phenomenon where the northernmost and southernmost regions of the Earth get little to no daylight, and for over 24 hours[3]. As for the midnight sun, it is similarly a phenomenon in which the sun does not set for over 24 hours but rather remains above the horizon[3][4].

Figure 2. Depiction of early afternoon from Tromsø, Norway, during a polar night.

During polar night, there is still weak filtered rays of sun that can create shades of twilight in the sky that range from blue, pink, and purple[5](Figure 2). It has also been documented that surrounding mountains cause the sun to not rise above the mountains, filling the day with almost total darkness, with the exception of dim daylight on clear days around noon[4][6]. Lights from the moon and stars still appear as well as northern lights, which can help to create reflections of light in the snow that has been referred to as "snowglow"[5].

The polar night and midnight sun events, including winter and summer months in general, have been hypothesized to either induce psychological effects such as SAD (seasonal depressive disorder), cause changes in length and quality of sleep, affect your circadian rhythm, and cause insomnia inducing changes to your endogenous melatonin production[2][3][4][7][5][6][8].

A majority of these findings were studied at Tromsø, Norway, a city that is North of the Arctic Circle, which experiences both Polar Night and Midnight Sun during the winter and summer months respectively.

Case Study: Tromsø, Norway

Figure 3. A map of Europe with Oslo, Tromsø, and Longyearbyen highlighted

Tromsø, Norway is a city located in Norway that has an extreme latitude of 69° N, above the Arctic Circle[3]. Tromsø experiences both polar night and midnight sun, with polar night lasting around 2 months between mid November to mid January[7], with about 2-5 hours of civil twilight each day[3]. Midnight Sun lasts nearly 2 months as well, between late May to late July[7]. While there are places higher North of the Arctic Circle that are still inhabitable, Tromsø serves as a good study case, as the population sample is large enough. Tromsø is in-between two other locations that receive limited daylight as well, such as Svalbard and Oslo, both located 78° N and 59° N respectively (Figure 3).

Figure 4. Sunrise, sunset, and civil twilight times in Oslo, Tromsø, and Svalbard during mid January, 2015

The current amount of civil twilight in Tromsø happens between around 8am to 10am and 2pm to 4pm during the middle of the winter season (mid January). Comparing this with Oslo and Svalbard, Oslo gets considerably more sun than Tromsø, being just South of the Arctic Circle, and Svalbard, having zero sun during mid January, experiencing the polar night for 4 months rather than 2[3](Figure 4).

Tromsø has been studied a variety of times, both with a focus on residents of the city as well visitors. They have done data collecting on sleep problems, mental distress, and effects of SAD[3][6][9]. Most of these are done via surveys, and the results have been varied enough to contradict findings with one another. While some studies do contradict one another, there has been a general consensus that in Tromsø, residents are typically more tired during winter months[3] and during the mornings[5], though some of the results are more negligible when compared to the theory of latitude hypothesis, relating to SAD and the effects. These general results all have relations to melatonin production and light, with data having been taken from both men and women, individuals with insomnia, and the working and unemployed[7][9]. The research will be more closely investigated throughout the wiki page.

Latitude Hypothesis and Implications of SAD

Latitude hypothesis is implied to mean that as latitude increases, rates of SAD should increase as well, based on previous observations[3]. SAD, otherwise known as Seasonal Affective Disorder, is a mood disorder that is described as a "recurrent pattern of seasonal depression, most often occurring during winter"[3]. Considering that SAD increases depressive symptoms, especially during the winter, the idea of latitude affecting rates of SAD became a well known myth, as polar nights were spent primarily in darkness. These depressive symptoms include feelings of low energy, instances of overeating, oversleeping, and disrupted sleep[5], however these may be the result of other factors. Further tests had shown that artificial light therapy had an impact in alleviating depressive symptoms during winter, however self-reported tests on the residents of Tromsø failed in finding any significant link to SAD with the coming of these seasonal geographical variations[3].

Rather, an interesting link was found between having a positive mindset on winter when correlating to wellbeing[3][5]. The research had surveyed Oslo, Tromsø, and Svalbard, using what was called the "Winter Mindset Scale" to measure resident attitudes towards winter and the effect it would have on their mental distress and wellbeing related to life satisfaction and positive emotions[3]. There was variability in how the weather affected individual moods, as some had positive boosts in their mood while others were more depressive. Research had found that these moods were more so affected by their subjective opinions, rather than the objective amount of daylight[3]. Having a positive interpretation of winter has been proposed to support better outcomes, which could partially explain the number of thriving residents living near the Arctic Circle during the winter months[3].

The study found results that positive wintertime mindsets had a correlation with latitude, and that residents that lived farther north possessed more positive wintertime mindsets[3]. The association between mindset and wellbeing could be inferred to have a positive correlation. SAD has also been found to have less correlation to latitude in another research study, but instead suspecting that climate, genetic vulnerability, and socio-cultural context had a larger role in the relationship[6]. When surveying an Indigenous group, the Sámi, whose population spanned throughout regions near the Arctic circle, they found that SAD was far less frequent, and that their overall attitudes around winter and sleep was more relaxed, finding decreased rates of insomnia and more relaxed attitudes towards sleeping, leaving their children to self-regulate their sleep[5].

While decreased rates of insomnia could be found in the indigenous population and locals, there was still a large correlation found between latitude and sleeping problems[5], which has been attributed to the changing of daylight variation and subsequent shift in your circadian rhythm. Evidence was shown correlating sleep length to several individual factors such as social and cultural factors as well as latitude, however light exposure remains one of the most powerful factors to influence the circadian rhythm[2].

Circadian Rhythm and Melatonin Production

The circadian rhythm plays an integral part in the production of melatonin and thus, affects all matters related to sleep. Your circadian rhythm is described as a biological clock that is generally in tune with a time range of approximately 24 hours[9]. This in turn will influence your body temperature, health conditions, nutrition, and social schedules, with light exposure being a powerful factor in influencing your rhythm[9][2]. Sleep is deeply influenced by our circadian processes, and the lack of daylight during the winter and absence of night during the summer months in the Arctic and Antarctic Circle can have significant influence on our sleep quantity and quality[8]. In Figure 5, Tromsø is shown to have a large change in hours of daylight during the summer and winter months, with a timeframe of around May-July showing around 24 hours of daylight, to the winter months of mid November to mid January showing 0 hours of daylight[7].

Figure 5. Monthly variations in hours of daylight on different latitudes, depicting Tromsø in blue.

Without the proper external time cues to determine our day-night cycle, our melatonin production has become suppressed and can desynchronize with our typical rest-work cycle, causing mild to moderate insomnia[8]. One research study had shown a significant decrease in quantity of sleep during both the polar night and midnight sun, with participants experiencing a mean sleep duration of above 500 mins (6 hours and 40 mins), while the midnight sun had experienced a slow decrease each night to only 330 mins (5.5 hours) by Friday, from sleep quantity measurements from Sunday to Friday. These results show a severe deficit in sleep as a result of these geographical phenomena, with hours of sleep that are not sufficient to allow an individual to maintain an optimal cognitive performance over the span of a week[8]. In comparison, another research journal reported that sleeping closer to the Antarctic Circle could result in longer sleep durations when compared to those closer to the Equator[2]. This also applied to those who lived at higher altitudes in the northern hemisphere. When comparing residents of Tromsø, Norway to residents of Accra, Ghana (located at 5°N, near the Equator), the difference in sleep was 21-55 minutes more for residents of Tromsø[2].

Your sleep-wake cycle can also be affected if you typically spend a majority of your time indoors, where the lack of natural light is apparent[5]. Evidence shows that melatonin production is greater during the winter months at high latitudes, which can lead to an increase in fatigue and negative moods. During the summer, our circadian rhythm is more affected compared to during the winter, due to the brighter lighting of summer[8]. Summer months in the Arctic Circle show delayed melatonin production as a result of the exposure to light during the evening, as part of the midnight sun phenomenon[8]. During the winter months, particularly during the peak of the polar nights, our bodies can show a large spike in melatonin, with levels decreasing as the winter months end[5]. As our circadian rhythm continues to shift further, our melatonin production appears to become aligned with our sleep schedules, thus obtaining less sleep and waking up during the middle of the night for longer periods of time[8].

In order to prevent shifting of your circadian rhythm during these geographical phenomena, research suggests that having a naturalistic dawn signal or gradual reduction of light can help to prevent a delay[4][5], as to prevent evening light exposure from causing delayed melatonin production, which would result in a later bedtime[8]. Light has a much greater effect on melatonin production during winter nights, and reduces melatonin production more efficiently[4].

Comparison & Conclusion

When comparing Tromsø to other cities at different latitudes, the results have been non-conclusive when relating to reports of increased mental distress. I believe that most mental distress is a result of other factors that affect you while living at Tromsø, such as the shifting of your circadian rhythm, thus causing the dysregulation of your endogenous melatonin production. Rather than your mental distress being caused directly by the change in latitude as a result of SAD, poor sleep can result in similar symptoms, such as depressive moods[3]. When doing a comparative study to Italy on the rates of SAD, research showed that there was no evidence to support higher rates of SAD as a result of latitude differences[3]. Having a positive winter mindset appears to be beneficial towards the mental health and sleep regulating processes of the residents living in higher latitudes. Considering that native groups living at those latitudes tend to do better with sleeping in those conditions, it may be a result of learning to have a positive mindset regarding winter as a whole.

However, when comparing sleep duration to places with higher latitudes, according to one research journal, there is a significant association of higher latitudes resulting in longer sleep durations. The country of Chile spans across the latitudes of 18°29S to 53°18S. Those who were closer to the Antarctic Circle had reportedly longer sleep durations compared to those who were closer to the Equator[2]. This lines up with the increased sleep duration of Norwegians in Tromsø, Norway to Ghanaians in Accra, Ghana. Accra is only 5°N of the Equator, and the difference in reported sleep averages at over half an hour. This suggests that there is a latitude-dependent trend of shorter sleep duration when close to the Equator[2], however the effects of polar night and midnight sun appear to have a stronger effect on sleep issues as a result of more extreme geographical changes in daylight during the winter and summer months. The changes to our circadian rhythm as a result of the lack of change in the daylight cycle can have a negative impact on our melatonin production, which can result in more severe losses of sleep and negative moods.

References

  1. ↑ Nag, O. S. (2021, March 19). Circles of latitude and longitude. WorldAtlas. https://www.worldatlas.com/geography/circles-of-latitude-and-longitude.html
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Brockmann, P. E., Gozal, D., Villarroel, L., Damiani, F., Nuñez, F., & Cajochen, C. (2017). Geographic latitude and sleep duration: A population-based survey from the Tropic of Capricorn to the Antarctic Circle. Chronobiology international, 34(3), 373–381. https://doi.org/10.1080/07420528.2016.1277735
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 Leibowitz, K., & Vittersø, J. (2020). Winter is coming: Wintertime mindset and wellbeing in Norway. International Journal of Wellbeing, 10(4), 35–54. https://doi.org/10.5502/ijw.v10i4.935
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Bratlid, T., & Wahlund, B. (2003). Alterations in serum melatonin and sleep in individuals in a sub-arctic region from winter to spring. International Journal of Circumpolar Health, 62(3), 242–254. https://doi.org/10.3402/ijch.v62i3.17561
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 Benke, E. (2025, January 7). What can we learn about sleep from the land of the Polar Night. BBC News. https://www.bbc.com/future/article/20250103-what-people-living-in-the-arctic-polar-night-teach-us-about-sleep
  6. ↑ 6.0 6.1 6.2 6.3 Johnsen, M.T., Wynn, R. & Bratlid, T. (2012) Is there a negative impact of winter on mental distress and sleeping problems in the subarctic: The Tromsø Study. BMC Psychiatry 12, 225. https://doi.org/10.1186/1471-244X-12-225
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Sivertsen, B., Friborg, O., Pallesen, S., Vedaa, Ø., & Hopstock, L. A. (2020). Sleep in the land of the midnight sun and polar night: The Tromsø study. Chronobiology International, 38(3), 334–342. https://doi.org/10.1080/07420528.2020.1845191
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 Paul, M. A., Love, R. J., Hawton, A., & Arendt, J. (2015). Sleep and the endogenous melatonin rhythm of high Arctic residents during the summer and Winter. Physiology & Behavior, 141, 199–206. https://doi.org/10.1016/j.physbeh.2015.01.021
  9. ↑ 9.0 9.1 9.2 9.3 Johnsen, M. T., Wynn, R., Allebrandt, K., & Bratlid, T. (2013). Lack of major seasonal variations in self reported sleep-wake rhythms and chronotypes among middle aged and older people at 69 Degrees North: The tromsø study. Sleep Medicine, 14(2), 140–148. https://doi.org/10.1016/j.sleep.2012.10.014


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