A groundbreaking new study from the University of Montreal has revealed that caffeine, the world’s most widely consumed stimulant, tangibly disrupts the brain’s recovery during sleep—especially in younger adults. The researchers found that consuming caffeine in the hours before bedtime leads to more complex, “wake-like” brain activity at night and could hamper both mental and physical restoration, raising crucial questions for Thailand’s coffee- and tea-loving society regarding nighttime caffeine consumption and its impact on well-being (Neuroscience News).
For millions of Thais, an iced coffee or bubble tea after dinner is a daily habit, a pick-me-up for students burning the midnight oil or professionals facing late-night work. But this new research, published in Nature Communications Biology in April 2025, shows that even a moderate evening dose of caffeine can significantly alter the brain’s sleep rhythms, keeping it more awake and less able to recuperate. This effect is particularly pronounced in those aged 20 to 27, owing to age-dependent differences in brain chemistry.
Announced on May 29, 2025, the study involved a collaboration between leading neuroscientists and sleep researchers at the Université de Montréal’s Cognitive and Computational Neuroscience Laboratory (CoCo Lab), the Centre for Advanced Research in Sleep Medicine, and the Quebec AI Institute (Mila). Using advanced artificial intelligence and electroencephalography (EEG), the research team analyzed sleep in 40 healthy adults across two different nights—one following caffeine consumption (200mg, roughly two cups of coffee) and another after a placebo. The subjects’ brain activity was closely monitored, focusing on the non-rapid eye movement (NREM) phase of sleep, vital for memory and cognitive recovery.
The results were striking: caffeine triggered more complex, less predictable brain signals, with the EEG showing a reduction in theta and alpha waves—those associated with deep, restful sleep—while boosting beta waves commonly found in alert, waking states. This shift in brainwave patterns, described as an increase in “criticality”—the balance point between order and chaos in neural activity—means the sleeping brain remains in a more activated, less restorative condition. “Criticality describes a state of the brain that is balanced between order and chaos,” explained the CoCo Lab’s director, who co-led the research. “It’s like an orchestra: too quiet and nothing happens, too chaotic and there’s cacophony. Criticality is the happy medium. In this state, the brain functions optimally: it can process information efficiently, adapt quickly, learn, and make decisions with agility.” But caffeine appears to push the brain toward a more reactive, less restful ‘orchestra performance’—even during sleep (Neuroscience News).
Importantly, these neural disruptions were most acute among young adults in their 20s. The study’s senior sleep scientist explained this by highlighting the role of adenosine, a molecule that builds up during waking hours and makes us feel sleepy. Caffeine works by blocking adenosine receptors in the brain—yet these are more numerous in younger people. As the researcher observed, “Adenosine receptors naturally decrease with age, reducing caffeine’s ability to block them and improve brain complexity, which may partly explain the reduced effect of caffeine observed in middle-aged participants. Younger brains, as a result, may be more susceptible to the stimulant effects of caffeine.”
These findings have particularly significant ramifications for Thailand, where energy drinks, tea, traditional Thai coffee, and even caffeinated herbal tonics are deeply integrated into daily routines. Students facing university entrance exams, night-shift workers, taxi drivers, and medical personnel are among those who may be inadvertently compromising their nightly recuperation through late-day caffeine intake. In Bangkok’s bustling 24-hour culture, the thirst for alertness can translate into chronically insufficient sleep quality—and, according to this new research, more than just a little tossing and turning.
Electroencephalogram (EEG) traces in the Montreal study showed that after evening caffeine consumption, the natural “slow-wave” sleep rhythms were attenuated, while “beta” activity—signifying alertness—was significantly enhanced. This shift correlates with a subjective sense of restlessness or surface-level sleep, even if total sleep time isn’t clearly diminished. Artificial intelligence models used in the study confirmed these subtle changes in neural complexity, offering new tools for the precise measurement of sleep disruption. Study first author Philipp Thölke described their approach: “We used advanced statistical analysis and artificial intelligence to identify subtle changes in neuronal activity. The results showed that caffeine increased the complexity of brain signals, reflecting more dynamic and less predictable neuronal activity, especially during the non-rapid eye movement phase of sleep that’s crucial for memory consolidation and cognitive recovery.”
In practical terms, this means that drinking caffeine before bed not only causes subjective difficulties in falling or staying asleep but may also hinder the brain’s ability to recover, consolidate memories, and prepare for the physical and mental demands of the following day. This could be especially problematic for young people whose academic or professional success depends on these vital overnight processes.
Thailand’s education system already contends with well-documented student stress and sleep deprivation. A 2023 national survey by the Ministry of Public Health found that more than 60% of high school students in Bangkok reported routinely sleeping less than the recommended 8 hours per night—many citing excessive study and high caffeine consumption as factors (Bangkok Post). This new study suggests that even if they carve out enough time to sleep, their brains may not attain the restorative “deep” phases necessary for optimal function if caffeine is consumed in the evening.
The cultural popularity of cafes, especially among younger Thais, has exploded. A recent market analysis noted that the Thai coffee industry is worth more than 70 billion baht annually, with “after-dinner” drinks and desserts driving much of the nighttime business (Bangkok Post). The appeal of energy drinks—often marketed for their stamina and concentration-boosting effects—adds another layer of public health concern. Thailand ranks as one of the top global consumers of energy drinks per capita (World Population Review), and these beverages often contain up to triple the caffeine found in a standard Thai coffee.
The Montreal study is groundbreaking not only for its technical approach—using AI to quantify brainwave changes—but also for raising public health questions relevant to local cultures. As noted by Professor Karim Jerbi, “While caffeine’s daytime alertness effect is well-known and often beneficial, its consequences on nighttime sleep require much more public attention, particularly among high-risk groups.”
For Thai parents, educators, and employers, these findings present a pressing dilemma: how to balance the immediate benefits of caffeine with its less visible—but potentially profound—impacts on brain health and performance. As the research team concluded, “Given caffeine’s widespread use around the world, especially as a daily remedy for fatigue, it’s crucial to understand its complex effects on brain activity across different age groups and health conditions.” The authors urge further exploration into how these neural changes—especially the shift to ‘wake-like’ criticality during supposed sleep—affect not just cognitive health and performance, but also emotional well-being and long-term metabolic health.
Data from the study indicate that for those in their 20s, even consuming caffeine as much as three hours before bedtime may be enough to trigger measurable sleep architecture changes. For older adults, the effect is less pronounced, but by no means absent—reminding a wider swath of the public to reconsider their late-day caffeine rituals.
This work builds on a growing international consensus linking caffeine with sleep disruption. A major systematic review published in Sleep Medicine Reviews (2018) documented chronic negative sleep effects from afternoon and evening caffeine intake (ScienceDirect). Meanwhile, the US National Sleep Foundation still recommends avoiding caffeine at least six hours before bedtime (Sleep Foundation)—advice echoed by Thai sleep physicians.
Historically, caffeine has played a major role in Thai hospitality and daily life. From piping cups of ‘oleang’ at bustling street stalls to the ceremonial serving of green tea in family gatherings, its mythology is as strong as its flavor. Yet, as this new scientific evidence suggests, informed consumption is essential. The sleepless student huddled at a Chiang Mai café or the night-shift security guard in Patong may be unwittingly sabotaging the very focus or energy they seek to enhance through late-night caffeine.
Looking forward, experts suggest several actionable steps for Thai readers. First, be mindful of the “hidden” sources of caffeine—not only coffee, but also teas, sodas, chocolates, herbal drinks, and especially energy beverages. Second, prioritize caffeine intake for earlier in the day, reserving evenings for non-caffeinated alternatives that support relaxation, such as chamomile tea, pandan leaf infusions, or traditional warm milk. Third, those in the high-risk young adult group—students, new professionals, and athletes—should strictly limit after-dinner caffeine if experiencing signs of poor sleep: difficulty falling or staying asleep, daytime grogginess, irritability, or poor focus.
For public health officials and educators, the challenge will be to communicate these nuances without demonizing caffeine entirely—respecting its role in Thai culture and productivity while providing new guidelines grounded in cutting-edge neuroscience. As research continues to unlock the intricate connections between daily habits and brain health, Thais are encouraged not to abandon their café culture, but to cultivate smarter consumption habits that promote truly restful nights and sharper, more creative days.
For those concerned about their sleep, practical changes can start tonight: opt for caffeine-free drinks after 3 pm, experiment with herbal alternatives, and pay attention to how your body responds. As Thailand balances tradition with modern science, supporting brain health through smarter sleep may become as essential as the daily cup itself.
[Sources: Neuroscience News, University of Montreal, Nature Communications Biology, Bangkok Post, Sleep Medicine Reviews, US Sleep Foundation, World Population Review]