A concussion, or mild traumatic brain injury (mTBI), occurs when the brain is violently shaken or jolted inside the skull following a blow or sudden force. This physical trauma initiates a cascade of events that frequently results in a wide array of symptoms, including disturbances to sleep. Sleep complaints, such as difficulty falling asleep (insomnia), excessive daytime sleepiness (hypersomnia), or fragmented rest, are among the most prevalent issues reported after a concussion. Understanding the biological reasons behind these sleep-wake cycle disruptions is the first step toward effective recovery.
The Neurological Impact on Sleep Regulation
The physical force of a concussion causes the brain to move rapidly, leading to damage in deep structures that govern arousal and sleep. This mechanical jarring can cause a temporary functional lesion in the brainstem, a primary control center for consciousness and sleep initiation. The injury triggers a pathophysiologic cascade, including ionic imbalance and the release of excitatory chemicals.
A concussion can also affect the hypothalamus, which regulates the sleep-wake cycle. Trauma to this area can disrupt the brain’s ability to cycle normally through non-rapid eye movement (NREM) and rapid eye movement (REM) sleep stages. This disruption makes it challenging for the brain to transition into and maintain the deeper, restorative phases of sleep. The resulting inflammation, or edema, can further irritate these neural networks, interfering with their function.
Disruption of Sleep-Wake Neurotransmitters
Structural damage from a concussion disrupts the balance of sleep-regulating neurotransmitters. The injury triggers the release of excitatory neurotransmitters, which keep the brain alert and active. This increased excitation counteracts the brain’s attempt to transition into a restful state, contributing to insomnia and sleep fragmentation.
The trauma can also reduce the effectiveness of inhibitory neurotransmitters, such as Gamma-Aminobutyric Acid (GABA) and Serotonin, necessary to calm neural activity and promote sleep. Additionally, the system involving Orexin (Hypocretin), a neuropeptide produced in the hypothalamus that promotes wakefulness, can become dysregulated. Loss of Orexin-producing neurons can impair the brain’s ability to maintain consolidated periods of wakefulness, leading to excessive daytime sleepiness.
Dysfunction in the production or timing of melatonin, a hormone that signals night, is another common consequence. Studies have documented a decrease in melatonin levels following an acute injury, which impacts sleep initiation. This chemical imbalance prevents the brain from receiving timely signals to wind down, leading to difficulty falling asleep and poor sleep efficiency.
Circadian Rhythm Misalignment
A concussion can disrupt the body’s internal 24-hour clock, known as the circadian rhythm. The master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which synchronizes physiological rhythms. Trauma can affect the SCN itself or the pathways that relay environmental information, particularly light exposure, to this master clock.
Disruption to the SCN can cause desynchrony, where internal rhythms are no longer working together effectively. This misalignment can manifest as a phase shift, meaning the timing of the sleep-wake cycle is either delayed or advanced relative to the external environment.
This problem is often compounded by secondary effects of concussion, such as light sensitivity or visual issues, which interfere with the SCN’s ability to receive accurate light signals. The resulting circadian rhythm disturbance is a common outcome that can hinder recovery by impairing cognitive functions and reducing neurogenesis.
Strategies for Restoring Healthy Sleep
Restoring healthy sleep patterns supports the brain’s healing process and clears neurotoxic waste through the glymphatic system. The most effective strategy involves adhering to a consistent sleep schedule by setting the same wake-up and bedtime every day, including weekends. This regularity helps to re-entrain the disrupted circadian rhythm.
The sleep environment should be cool, dark, and quiet to promote restful sleep. Establish a relaxing routine, such as deep breathing exercises or a warm bath, for an hour before bed to signal the brain to wind down. Avoiding bright screens and electronic devices within an hour or two of bedtime is important because blue light can block the signals that allow sleep to occur.
Limiting daytime naps is important; if a nap is necessary, it should be kept short (20 to 30 minutes) and avoided later in the afternoon. Stimulants like caffeine and nicotine should be avoided within several hours of bedtime, as they interfere with sleep regulation. For persistent sleep difficulties, consult a healthcare provider or sleep specialist to assess for specific disorders and discuss options like light exposure therapy or cognitive behavioral therapy for insomnia (CBT-i).