How to fall asleep quickly after working overtime and staying up late? My light therapy bedtime ritual.

Insomnia is a common sleep disorder in contemporary society, with complex and diverse causes. Among these, the heightened brain activity before sleep caused by "working overtime and staying up late" has become a significant and undeniable factor. Many people who work late or engage in mentally demanding tasks often experience this problem: their bodies are extremely tired, but once they lie down, their brains race like an out-of-control engine, with various thoughts flooding in, making it difficult to fall asleep. From a neurobiological perspective, this state is often accompanied by increased activity in the prefrontal cortex (PFC), particularly the dorsolateral prefrontal cortex (DLPFC) region responsible for planning, decision-making, and emotional regulation, which remains continuously activated, thus interfering with the natural sleep process. Further research suggests that excessive activity in the prefrontal β-θ network, which integrates memory and emotional functions, is likely a key cause of this type of "pre-sleep excitatory insomnia." 

01. A new explanation for insomnia: The "front desk" and "manager" in REM sleep are working overtime late at night. 

Traditional views suggest that the prefrontal cortex is typically in a relatively suppressed state during rapid eye movement (REM) sleep, the stage where most dreaming occurs. However, researchers using intracranial electrode recordings have found that two key areas in the human prefrontal cortex—the dorsolateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC)—remain highly active during REM sleep, forming an efficient "theta/beta oscillation network." The DLPFC acts like the brain's "chief executive officer," leading higher cognitive functions such as logical analysis, decision-making, and planning; the ACC acts as the "emotion and conflict monitoring director," responsible for emotional processing and error detection. Further analysis using sample entropy brain topography revealed that changes in brain activity during REM sleep are mainly concentrated in the prefrontal cortex. The β and θ rhythms in this region maintain functional coordination, indicating that the prefrontal cortex is not completely "silent" throughout the sleep cycle but remains physiologically active. If this region cannot effectively "downregulate" before sleep, it can easily lead to difficulty falling asleep, shallow sleep, and excessive dreaming [1, 2]. These studies suggest that the prefrontal cortex is not completely shut down during sleep. If it remains in a highly excited state before sleep, it will be difficult for it to smoothly transition to the low-frequency rhythms required for sleep. Imagine that when you work late into the night, the DLPFC and ACC are in a highly activated state, continuously engaging in neural "dialogue" using theta waves (4–8 Hz) and beta waves (15–35 Hz). If you then try to force them to "shut down," these two brain regions will remain active because cognitive and emotional tasks have not yet been completed. This means that when you want to rest, your brain is actually still "working overtime," leading to typical "insomnia caused by staying up late." Therefore, the DLPFC-ACC functional network has become a precise target for intervening in "pre-sleep excitatory insomnia."

02. Transcranial photostimulation: A non-invasive neuromodulation technique

Transcranial photobiomodulation (tPBM) is a technique that uses near-infrared light to penetrate the skull and act on neurons in the cerebral cortex. Studies have shown that near-infrared light of specific wavelengths (such as 808 nm and 1064 nm) can regulate mitochondrial function, promote adenosine triphosphate (ATP) synthesis, replenish energy for fatigued neurons, improve cerebral blood flow and oxygenation levels, and modulate neuronal excitability. In insomnia intervention, tPBM is used for localized and precise stimulation of the prefrontal cortex, reducing excessive prefrontal cortex activity. Its mechanisms include [2]: inhibiting excessive neuronal firing by regulating ion channels and neurotransmitter release; enhancing the GABAergic system by promoting the function of the inhibitory neurotransmitter GABA to reduce excessive prefrontal cortex activity, allowing the brain to switch from "fight-or-flight mode" to "rest mode"; and regulating brain network synchronicity by promoting rhythmic coordination between the prefrontal cortex and sleep-regulating nuclei (such as the preoptic area and thalamus).

03. Clinical and research support 

According to preliminary clinical trial results, five consecutive days of transcranial photobiomodulation (tPBM) intervention targeting the prefrontal cortex resulted in improved sleep efficiency and increased rapid eye movement (REM) sleep percentage in participants.  Significant improvements in working memory were also observed on the fifth day, specifically in increased accuracy and reduced reaction time on the n-back task. Furthermore, the study found that a single 10-minute session of pulsed transcranial light stimulation effectively reduced daytime sleepiness and improved alertness the following day. This technology also helped alleviate anxiety, stress, and depressive symptoms, and enhanced alpha and gamma band brainwave power associated with relaxation and higher cognitive functions. These results suggest that transcranial light stimulation is a non-invasive and effective method for simultaneously improving sleep quality, daytime cognitive function, and emotional state [3, 4].

04. Outlook 

With the deepening understanding of sleep neural circuits and oscillatory rhythms, non-invasive neuromodulation techniques such as tPBM (transcranial photobiomodulation) show broad prospects in sleep medicine. In the future, it can be combined with real-time EEG feedback to achieve "closed-loop light stimulation," precisely regulating prefrontal cortex excitability and providing personalized treatment plans for insomnia patients.

References: 

1. Frontal beta-theta network during REM sleep. Elife. 2017 Jan 25;6:e18894.

2. Effects of stimulating frequency of NIR LEDs light irradiation on forehead as quantified by EEG measurements. J Innovative Optical Health Sciences 2021, 14(02) 2050025. 

3. Advanced Intervention Effects of Pulsed and Steady Transcranial Photobiomodulation on Sleep, Mood, and EEG Signal Regulation. J Biophotonics. 2025 Jun;18(6):e70004. 4. Brain Photobiomodulation Improves Sleep Quality in Subjective Cognitive Decline: A Randomized, Sham-Controlled Study. J Alzheimers Dis. 2022;87(4):1581-1589.

Disclaimer: This article is for educational purposes only and should not be considered a substitute for professional medical advice. If you are suffering from chronic insomnia, please consult a doctor or sleep specialist.