Insomnia and Circadian Rhythm Disruption After Brain Injury

Some caregivers describe it as the household running on two clocks. He's wide awake at 2 a.m., moving around the kitchen like it's the middle of the afternoon, and by the time everyone else is having lunch, he's asleep on the couch again. It doesn't look like insomnia in the way most people picture it, tossing and turning, unable to drift off. It looks like the whole schedule has come unstuck from the actual time of day. Both patterns, the classic can't-fall-asleep insomnia and the clock-drift version, are common after brain injury, and they come from different places.

How Common This Actually Is

A meta-analysis of 21 studies covering 1,706 adults with traumatic brain injury found that half reported some form of sleep disturbance, and 25 to 29 percent went on to receive a diagnosed sleep disorder (Mathias & Alvaro, 2012, Sleep Medicine). Insomnia specifically has been studied in more detail for mild TBI: a systematic review and meta-analysis pooling nearly 100,000 people across 19 studies found a pooled insomnia disorder rate of 27 percent, and a broader rate of 71.7 percent when counting insomnia symptoms rather than a full clinical diagnosis (Montgomery, Baylan & Gardani, 2022). Either way it's measured, insomnia after brain injury is common, not incidental.

Two Different Problems Wearing the Same Name

Insomnia and circadian rhythm disruption often get talked about together, but they're not the same mechanism. Insomnia is difficulty initiating or maintaining sleep, trouble falling asleep, trouble staying asleep, or waking far earlier than intended with no way back to sleep. It can trace back to direct damage in brain regions involved in sleep initiation, disruption of neuronal signaling from diffuse axonal injury, or hormonal systems knocked off balance by the injury itself, and it's frequently compounded by the pain, depression, or PTSD that often travels alongside a brain injury (Feasibility of Home-Based Measurement of Circadian Timing for Veterans With TBI and Insomnia, clinical trial background, NCT05665764).

Circadian rhythm disruption is a different problem: the body's internal clock losing sync with the actual day-night cycle. This can take the form of a delayed sleep phase, where a person's natural sleep window shifts hours later than it used to, or in less common cases, an irregular or "free-running" pattern where sleep timing drifts unpredictably day to day (Addressing sleep-wake disturbances in patients with traumatic brain injury, ACNR clinical review). The mechanism often involves disrupted melatonin regulation, since brain injury can affect the signaling pathway between the eyes and the brain structures that time melatonin release (Castriotta & Murthy, 2011, CNS Drugs).

The practical difference matters because the two don't respond to the same approach. Someone with insomnia driven by pain or depression needs those addressed directly. Someone with a shifted circadian clock may need light exposure timing, chronotherapy, or melatonin under a doctor's guidance, working on sleep hygiene alone won't fix a clock that's drifted, any more than insomnia treatment alone will fix a scheduling problem.

Why This Isn't Just a Willpower Problem

It's easy for families to read erratic sleep timing as a discipline issue, staying up too late, sleeping in too long, not "trying" to keep a normal schedule. The research doesn't support that read. Sleep-wake disturbances are reported by 50 to 70 percent of TBI patients regardless of injury severity, and changes in sleep architecture alone don't fully explain how intense or persistent these disturbances are, which is part of why researchers now look specifically at circadian timing system damage as a separate contributing factor, not just a downstream symptom of poor sleep (Sleep and circadian rhythms after traumatic brain injury, systematic literature review). This is a physiological disruption, not a scheduling habit that better willpower would fix.

When to Get a Formal Evaluation

If sleep timing has become unpredictable, or if falling and staying asleep has been a persistent struggle since a brain injury, that's worth bringing to a sleep specialist directly, and naming both patterns separately: "I can't fall asleep" is different information than "I'm asleep at completely the wrong hours." A formal evaluation, sometimes including actigraphy to track sleep-wake timing over days or weeks, can determine which mechanism is actually driving the disruption, and that distinction is what determines which treatment has a chance of working.

Sources

1. Mathias, J.L. & Alvaro, P.K. (2012). Prevalence of sleep disturbances, disorders, and problems following traumatic brain injury: a meta-analysis. Sleep Medicine, 13, 898-905. PMID 22705246.
2. Montgomery, M.C., Baylan, S., Gardani, M. (2022). Prevalence of insomnia and insomnia symptoms following mild-traumatic brain injury: A systematic review and meta-analysis. PMID 35033968.
3. Castriotta, R.J. & Murthy, J.N. (2011). Sleep disorders in patients with traumatic brain injury: a review. CNS Drugs, 25(3), 175-185. PMID 21062105.

Note: two additional sources referenced in the mechanism discussion (a clinical trial background summary and a clinical review site) are lower-tier than the peer-reviewed citations above and are named inline rather than numbered; consider replacing with a primary peer-reviewed circadian-TBI paper before this goes live if a stronger source is preferred.