The physical symptoms of fever are well researched and documented; however, a much stranger and less studied symptom is fever dreams.
Sickness can cause many physical effects, including chills, sweating, headaches, fatigue, and more (Ames et al. 2013). These are all symptoms of the body’s immune system fighting an infection (Mayo Clinic 2022). The less understood effect of a fever is fever dreams, they are often characterized by intense emotions, unnatural proportions, and a feeling that something is very wrong when nothing obviously frightening is happening (Shredl & Erlacher 2020). This raises a scientific question: why does being sick make dreams feel much stranger than usual?
During a fever, the body is not just “getting too hot.” During infection, immune signals alter the body’s temperature and send signals; one of these signalling molecules is a cytokine (Krueger 2016). Cytokines can also influence sleep and other behaviour during illness. Some cytokines, including interleukin-1 (IL-1) and tumour necrosis factor (TNF), interact with signalling pathways in the brain that help regulate sleep, particularly non-rapid eye movement sleep (Krueger & Majde 1994). This signalling molecule may help explain why sickness also causes fatigue and disrupts normal sleep patterns (Krueger & Majde 1994).
Infection itself can alter sleep. Research suggests that infectious illness can initially increase non-rapid eye movement sleep while suppressing rapid eye movement (REM) sleep; this raises questions since REM sleep is associated with vivid dreaming (Cerri et al. 2017). However, dreaming can occur outside REM sleep, and illness can fragment sleep, potentially creating more opportunities to remember dreams upon waking (Krueger & Opp 2016).
Temperature regulation and sleep are closely connected in the brain; some neural networks that control sleep overlap with those that maintain body temperature (Cerri & Amici 2021). One important region is the hypothalamus, particularly its preoptic area, which contains neural circuits involved in both sleep and temperature regulation (Cerri & Amici 2021). Even when sleeping, the brain still receives information from the body. During sleep, sounds or physical sensations can enter dreams; the same goes for feelings of heat, chills, discomfort, or sweating (Bach et al. 2002). These sensory inputs are theorized to influence dream content (Karacan et al. 1968). This could help explain why temperature-related imagery appears more often in fever dreams. However, it does not fully explain other unusual details reported, including spatial distortions such as moving walls or disproportional body parts, or the overall terrifying and uncanny nature of fever dreams (Schredl & Erlacher 2020).
This is where science becomes less certain. Evidence suggests fever dreams differ from ordinary dreams; fever affects immune signalling, sleep, and thermoregulation (Bach et al. 2002), but researchers have yet to identify why these dreams differ from regular dreams. Studying fever dreams is surprisingly difficult because researchers ideally need to locate people with fevers and monitor their temperature and sleep. Many existing studies rely on people remembering fever dreams afterward, creating a recall bias and making conclusions difficult to draw (Shredl & Erlacher 2020; Karacan et al. 1968).
Fever dreams are, for now, best understood as normal dreaming that occurs in an abnormal physiological state. The dreaming brain still does what it normally does and constructs a world from the fragments of sensation it has. It is known that fevers change both the body and sleep, but it’s still unclear why these symptoms become distorted when we sleep (Shredl & Erlacher 2020).
References
Ames, Nancy J., Claudia Peng, John H. Powers, et al. 2013. “Beyond Intuition: Patient Fever Symptom Experience.” Journal of Pain and Symptom Management 46 (6): 807–16. https://doi.org/10.1016/j.jpainsymman.2013.02.012.
Bach, Veronique, Frédéric Telliez, and Jean-Pierre Libert. 2002. “The Interaction Between Sleep and Thermoregulation in Adults and Neonates.” Sleep Medicine Reviews 6 (6): 481–92. https://doi.org/10.1053/smrv.2001.0177.
Cerri, Matteo, Marco Luppi, Domenico Tupone, Giovanni Zamboni, and Roberto Amici. 2017. “REM Sleep and Endothermy: Potential Sites and Mechanism of a Reciprocal Interference.” Frontiers in Physiology (Switzerland) 8 (August): 624. PubMed. https://doi.org/10.3389/fphys.2017.00624.
Cerri, Matteo, and Roberto Amici. 2021. “Thermoregulation and Sleep: Functional Interaction and Central Nervous Control.” Comprehensive Physiology (United States) 11 (2): 1591–604. PubMed. https://doi.org/10.1002/cphy.c140012.
Karacan, I, S. M. Wolff, R. L. Williams, C. J. Hursch, and W. B. Webb. 1968. “The Effects of Fever on Sleep and Dream Patterns.” Psychosomatics (England) 9 (6): 331–39. PubMed. https://doi.org/10.1016/S0033-3182(68)71807-7.
Krueger, J. M., and J. A. Majde. 1994. “Microbial Products and Cytokines in Sleep and Fever Regulation.” Critical Reviews in Immunology (United States) 14 (3–4): 355–79. PubMed. https://doi.org/10.1615/critrevimmunol.v14.i3-4.70.
Krueger, J. M., and M. R. Opp. 2016. “Sleep and Microbes.” International Review of Neurobiology 131: 207–25. https://doi.org/10.1016/bs.irn.2016.07.003.
Mayo Clinic. 2022. “Fever – Symptoms and Causes.” Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/fever/symptoms-causes/syc-20352759.
Schredl, Michael, and Daniel Erlacher. 2020. “Fever Dreams: An Online Study.” Frontiers in Psychology 11 (January). https://doi.org/10.3389/fpsyg.2020.00053.
Comments
8 Responses to “Fever Dreams: Why do They Happen and Why Are They so Weird?”
Hi iSci,
With the freshman flu going around and people getting sick left and right the concept of rationalism had me beginning to think. Rationalism came up in Life Sciences, and it’s defined by the idea that every action has a cause. When I get sick, I have intense fever dreams that leave me shaken for days. While thinking of a topic for this blog post, I became curious about the science behind why they were happening.
Thanks and enjoy!
Cassia
Hi Cassia
I really like your entry on fever dreams because it definitely is a strange phenomenon that affects so many of us! Here are a few of my suggestions:
– I think you can combine paragraphs 2 and 3 to make the transition from cytokines to infection smoother. You can focus the paragraph on the effects of infection (not just temperature/fever related side effects) to help your ideas flow into each other.
– You might be able to merge paragraphs 4 and 5 about temperature regulation. I think this would help you explain how the physical inputs (like heat and chills) have psychological effects during sleep.
– Since fever dreams are such an interesting topic, I think you could alter your first sentence to really hook the reader from the start. Likewise, a gripping conclusion would leave a lasting impression, especially since there is so much more to be discovered on the topic!
Overall, I liked your post and I think your topic was fascinating to learn more about!
Naomi
Hi Cassia,
Your blog post is super fascinating and very relevant to the frosh flu going around! I really love how you explained how REM sleep plays a role and how you touched on how it is difficult to study fever dreams.
Some suggestions:
-P1S1: I think you are missing a year in the citation “Ames et al.”, or a “n.d.” after the et al. in case there isn’t a date.
-P1S4: Perhaps you could clarify what is meant by “unnatural scales” in the fever dreams; to me I think of musical scales, but it might make more sense to explain it!
-P3S2: When you say “suppressing rapid eye movement, or REM, sleep;” you could also write it as “suppressing rapid eye movement (REM) sleep” to fit in the abbreviation in a better flow.
Overall, awesome blog post and happy editing!
Heer
Hi Cassia!
Great post! Your choice of topic is very interesting as it was not one I knew much about before reading!
I just have a few suggestions that I think could strengthen your post:
– I think the capitalization in your title is slightly incorrect. The proper capitalization would be “Fever Dreams: Why Do They Happen and Why Are They so Weird?”
– This is not necessary, but consider adding a figure to your post to provide a visual aid to supplement the information you are conveying. To give some examples, this figure could illustrate the effect of sickness on REM sleep, the influence of cytokines, or the relationship between temperature regulation and sleep in the brain.
Happy editing!
Sofia
Hi Cassia,
I really liked the topic you chose for your blog, I’ve also experienced fever dreams so I was interesting in reading the science behind it!
A couple suggestions you can implement of you see fit include:
– When you’re explaining how temperature and sleep are connected in the brain, you could mention which regions of the brain this overlaps in to bring in neurobiological structures would deepen the reader’s understanding of your topic
– In P2S1-2, you mention how cytokines influence sleep and behavior. You could consider adding in an extra sentence to explain how the molecule actually does this in the brain if there are sources explaining its processes!
That was a great article, thanks for researching it so we could all learn more about fever dreams! I hope you have fun editing!
Emma Ramos
Hi Cassia!
Your blog post on fever dreams was really interesting! Here are a few suggestions to keep in mind while you edit:
-Change from “bibliography” to “references” when formatting in Chicago author-date format
-Consider splitting P5S2 for better flow
-For P5S2, if you decide to keep it as one sentence, place the in-text citation at the end of the sentence rather than in the middle
-I think it would be really cool to have a figure, maybe one about cytokine signaling during infection and how that can affect sleep.
Overall, wonderful job!
Happy editing!
Tessa
Hi Cassia!
I really liked how you explored a topic that many people may have experienced but don’t fully understand. Explaining how cytokines such as IL-1 and TNF affect sleep helped connect fever dreams to the body’s immune response. I also liked how you acknowledged the limitations of current research, especially how relying on people’s memories of their dreams can create recall bias.
One area that could be improved is the explanation of how changes in REM sleep relate to fever dreams. Although you mention that REM sleep may decrease during illness, explaining more clearly why dreams can still become so vivid would help readers understand this connection. Additionally, including a specific example from a fever dream study could help show how these dreams differ from ordinary dreams.
– Jua
Hey Cassia,
Awesome blog post; the link between cytokines and sleep was really interesting.
Here are some notes I had:
+ P2S3: I would swap the comma in “fever dreams, they are often…” with a semicolon or a period, as you see fit.
+ I believe you may have misspelled the citation (Schredl & Erlacher) a few times :))
+ I’m not sure, but it looks like your (Krueger 2016) reference in P3 should be (Krueger & Opp 2016), based on your references list.
Overall, great job!
Happy editing,
Amy