The Ultimate College Dilemma: Should I study or sleep?

By Pin Hsuan (Jessica) Yeh, Rumaisa Noorayn Subhani, and Saathvik Kochikar Pai

“Sleep or study?” Mary thought to herself. 

Mary is a college freshman encountering the dilemma faced by most college students at least once. Is it better to pull an all-nighter to study, or to sleep and allow the brain to process what it has learned?

To investigate how a lack of sleep affects our cognitive performance, researchers from Beijing Sport University and the Northwest University of Political Science and Law conducted a controlled experiment using a classic mental rotation task: an activity where participants decide whether two rotated letters are the same or mirrored. 

The study involved 24 healthy college students who were asked to perform this task twice: once after a normal night’s sleep, and again after staying awake for 36 hours. During both sessions, the researchers recorded brain activity using electroencephalography (EEG) and focused on a specific brain signal known as the P300 wave, which reflects attention and stimulus evaluation (Li et al., 2022).

So, what happened after the all-nighter? 

Unsurprisingly, the sleep-deprived participants’ performance dropped. Their reaction times slowed, and error rates increased, especially when letters were rotated at steeper angles, like 120 degrees. These results show that sleep deprivation makes it harder for the brain to perform tasks requiring spatial manipulation, like mentally flipping a puzzle piece to see if it fits. The ability to visualize, rotate, and compare objects in your mind is essential in subjects like organic chemistry, where students flip chemical conformations and identify stereoisomers by imagining molecules from different angles. This happens to be the class in which Mary has an upcoming exam.

In light of this finding, let’s explore what would happen if Mary decides to forego sleeping in favor of extra study time. Mary pulls an all-nighter, forcing herself to stay awake and review for her organic chemistry midterm. During the exam, Mary has a very hard time visualizing the molecules. Her ability to imagine and spin the molecules in her head has decreased significantly. What she was able to do easily the night before requires a herculean effort during the exam! This decrease in ability exemplifies the cognitive effects of sleep deprivation on the brain.

Furthermore, Mary’s dramatic drop in spatial reasoning can be explained through insights from brain activity. After sleep deprivation, the amplitude of the P300 wave decreased significantly, demonstrating the participants’ decreased ability to focus and process visual information. This decrease was particularly noticeable in brain regions tied to spatial reasoning, such as the parietal lobe and prefrontal cortex.

Even more interestingly, the study by Li et al., found that connectivity between certain brain regions changed following sleep deprivation. In particular, the authors found stronger signaling from the middle frontal gyrus to parts of the parietal lobe, a pattern that they believe may reflect the brain’s attempt to compensate for its weakened state. However, this increased effort proves insufficient to prevent performance from dropping. In fact, it seems the more the brain tries to compensate, the worse accuracy gets, suggesting an ineffective state of cognitive overdrive.

This study makes it clear that pulling an all-nighter doesn’t just make you tired: it fundamentally disrupts how your brain processes space and visuals. The brain might try to fight back, but in the end, sleep is not optional when it comes to optimizing cognitive function.

Returning to Mary’s dilemma: unfortunately, she is disappointed when she gets her exam results back the following week. She scored lower than she had on the previous midterm! Although she passed the test, she did not score as well as expected for the amount of studying she did. Feeling as though she must compensate for her performance in the second midterm, Mary puts in even more late nights of studying for the final and for her other classes, getting fewer than five hours of sleep every day. 

The day of the final arrives. Mary sleeps only 3 hours, yet she feels ready for the final. In the exam, the graphs and diagrams feel familiar but foggy. She is surprised, because she used to be able to decipher these images easily, but now she struggles to understand them. Overall, Mary is able to figure everything out, but it takes her much longer than it used to. She scores a B+ on the final, which is better than the midterm, so she decides to continue this strategy of sleeping less to do better in Organic Chemistry II. 

Next quarter, Mary feels tired and lethargic every day. She increasingly relies on coffee and energy drinks and has difficulty focusing. This is her brain failing to compensate for her lack of adequate sleep; it is affecting her cognitive abilities. 

In Mary’s case, the cost of cutting sleep isn’t just an immediate hit to alertness—it accumulates over weeks and months. Studies show that it is not a single all-nighter but instead sustained patterns of short or irregular sleep that most strongly undermine cognitive performance (Okano et al., 2019). Specifically, students who averaged longer, higher-quality, and more consistent sleep over the month and week leading into exams scored significantly higher, whereas a good night’s rest immediately before a test had little impact. This finding suggests that Mary’s habit of sleeping only three to five hours nightly will gradually erode her ability to consolidate new material, flexibly manipulate spatial information (e.g., molecular conformations in organic chemistry), and sustain the focused attention reflected in the P300 signal—effects that cannot be “caught on” with last-minute cramming.

But the consequences of sleep deprivation extend far beyond grades; chronic sleep loss also carries serious long-term health risks. The Institute of Medicine reports that consistently getting less than the advised 7–8 hours of sleep per night is associated with a dramatically higher likelihood of hypertension, impaired glucose tolerance and type 2 diabetes, obesity, depression, and even major cardiovascular events such as heart attack and stroke (American Academy of Sleep Medicine, 2011). At the hormonal level, short sleep downregulates leptin (the “satiety” hormone) and upregulates ghrelin (the “hunger” hormone), promoting weight gain, while systemic inflammation and immune dysregulation further undermine physical resilience. In other words, what begins as a strategy to squeeze in extra study time can, over months and years, undermine both Mary’s brain health and her overall well-being.

Evidently, chronic sleep loss carries significant consequences to one’s health, but is one all-nighter truly a problem? 

While one all-nighter can negatively impact cognitive function the following day, it is truly the inconsistent, low quality sleep patterns that cause the most harm. As college students, it is easy to get lost in the cycle of homework, studying, and extracurriculars, and one all-nighter can easily turn into a bad habit. However, making sure to consistently get enough sleep can make a difference in the quality of your work and interactions. So, the next time you, like Mary, face the dilemma of whether to study or sleep, consider sleeping as a form of preparation for an upcoming exam, because sleep might help you more than your cheat sheet.

What would you like to read about next? Let us know here!

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Written by Pin Hsuan (Jessica) Yeh, Rumaisa Noorayn Subhani, and Saathvik Kochikar Pai

Illustrated by Pin Hsuan (Jessica) Yeh

Edited by Vidya Saravanapandian, Janie Oberhauser, Dhruv Mehrotra

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References

American Academy of Sleep Medicine. (2011, July 1). IOM report emphasizes the role of sleep in preventing early childhood obesity. https://aasm.org/iom-report-emphasizes-the-role-of-sleep-in-preventing-early-childhood-obesity

Li, Y., Ma, M., Shao, Y., & Wang, W. (2022). Enhanced effective connectivity from the middle frontal gyrus to the parietal lobe is associated with impaired mental rotation after total sleep deprivation: An electroencephalogram study. Frontiers in neuroscience, 16, 910618. https://doi.org/10.3389/fnins.2022.910618 

Okano, K., Kaczmarzyk, J. R., Dave, N., Gabrieli, J. D. E., & Grossman, J. C. (2019). Sleep quality, duration, and consistency are associated with better academic performance in college students. NPJ science of learning, 4, 16. https://doi.org/10.1038/s41539-019-0055-z