A concussion is a mild traumatic brain injury occurring when a jolt or blow to the head or body causes the brain to move rapidly inside the skull. This sudden movement temporarily disrupts normal brain function. While often considered “mild,” concussions can significantly impact various brain functions, including sleep. Many individuals experience difficulty sleeping after a concussion, a common and frustrating symptom. This article explores the underlying reasons why a concussion interferes with the ability to fall and stay asleep.
Neurological Disruption and Brain Chemistry
A concussion initiates a complex series of biological changes within the brain. One significant consequence is an “energy crisis,” where brain cells struggle to produce and utilize energy effectively. This metabolic mismatch occurs because the brain’s demand for glucose, its primary fuel, increases while blood flow, which supplies this glucose, may decrease.
This injury also disrupts the delicate balance of neurotransmitters, chemical messengers essential for regulating sleep and wakefulness. For instance, an imbalance can occur between excitatory neurotransmitters like glutamate and inhibitory ones like GABA. Changes in serotonin and melatonin pathways, hormones that promote sleep, can also occur, complicating the brain’s ability to transition into a restful state.
Additionally, the brain responds to injury with inflammation. This inflammatory response involves the activation of certain cells and the release of pro-inflammatory chemical messengers. While inflammation is part of the healing process, prolonged inflammation can inhibit brain cell repair and interfere with sleep-promoting signals, including melatonin production.
Physical and Cognitive Symptoms
Beyond chemical changes, the direct physical and cognitive symptoms of a concussion present significant barriers to sleep. Headaches are a common symptom, often throbbing or persistent, and this discomfort alone can make it difficult to relax and fall asleep. Other physical symptoms like dizziness, nausea, or neck pain further contribute to an uncomfortable state, making rest elusive.
Heightened sensitivity to light (photophobia) and sound (phonophobia) are also frequent after a concussion. Even dim lights or quiet sounds can feel overwhelming, preventing the brain from quieting down for sleep. This sensory overload makes creating a conducive sleep environment challenging.
Cognitive symptoms, such as mental fogginess, difficulty concentrating, or feeling “slowed down,” can paradoxically make the brain feel “wired” when attempting to sleep. The effort required for daily tasks can leave the brain exhausted yet unable to shut off. This persistent mental activity and an inability to quiet thoughts make initiating and maintaining sleep extremely difficult.
The Body’s Stress Response and Hyperarousal
A concussion is perceived by the body as a significant injury or stressor, triggering a natural protective mechanism. This activates the sympathetic nervous system, commonly known as the “fight or flight” response. This system prepares the body for perceived threats, leading to a state of heightened physiological arousal.
This hyperarousal manifests as an increased heart rate, elevated adrenaline levels, and a general feeling of alertness or anxiety, even when an individual is trying to rest. The body remains on high alert, as if facing an ongoing threat, making it challenging to relax muscles and calm the mind. This physiological state actively works against the body’s natural transition into a relaxed, sleep-ready condition.
The sustained activation of the sympathetic nervous system can disrupt the normal sleep-wake cycle and contribute to sleep fragmentation. This means individuals may find it hard to fall asleep, wake up frequently during the night, or experience unrefreshing sleep. The body’s protective stress response, while intended to aid survival, inadvertently interferes with the restorative processes of sleep following a concussion.