Why do I grind my teeth at night? What the clinical trials show

Why do I grind my teeth? It’s multifactorial, not just stress

If you ask why do I grind my teeth, the common answer points to stress. The evidence shows the picture is more complicated. Bruxism, the clinical term for teeth grinding and jaw clenching, arises from a cluster of interacting factors rather than a single cause.²

The current scientific consensus frames bruxism through a biopsychosocial model. This means biological factors (sleep architecture, neurotransmitter activity, genetic predisposition), psychological factors (anxiety, depression, perceived stress), and social factors (lifestyle habits, occupational demands) all contribute.² No one factor alone predicts who will grind their teeth.

Insomnia and poor sleep quality show a clear association with sleep bruxism. A 2026 meta-analysis found that adults with insomnia have significantly higher rates of sleep bruxism compared to those without sleep disturbances.¹ This link runs in both directions: bruxism disrupts sleep, and disrupted sleep worsens bruxism.

One popular belief ties bruxism to obstructive sleep apnea (OSA). Multiple systematic reviews have tested this association. A 2024 meta-analysis concluded that sleep bruxism may not be associated with OSA after controlling for confounding variables.⁴ Two earlier systematic reviews reached similar conclusions: the prevalence of bruxism in OSA patients does not differ meaningfully from the general population.⁵⁶ If you have both conditions, treating one does not reliably resolve the other.

Awake bruxism, the daytime form, shows different patterns. A 2025 meta-analysis of population studies found that awake bruxism prevalence varies widely across studies, ranging from 6% to over 30% depending on diagnostic criteria and population demographics.³ The variability underscores the role of context-specific stressors and habits.

Why do I grind my teeth at night, but not during the day?

Sleep bruxism and awake bruxism are distinct conditions with different triggers. Sleep bruxism occurs during sleep, most often during stage 2 non-REM sleep and during transitions between sleep stages. It manifests as rhythmic or sustained jaw muscle contractions outside conscious control.

Awake bruxism happens during waking hours and is often a semi-conscious habit. It tends to cluster during periods of concentration, stress, or physical exertion. Many people who grind their teeth at night do not grind during the day, and vice versa.³

The mechanisms diverge. Sleep bruxism appears tied to autonomic nervous system arousals, brief activations of the sympathetic nervous system that occur during sleep. These arousals trigger increased heart rate, changes in breathing, and jaw muscle contractions. Awake bruxism links more directly to psychological states, habit loops, and learned patterns of jaw tension.

One systematic review examined the relationship between snoring and bruxism. Snoring, another disorder of sleep-related muscle activity, co-occurs with sleep bruxism more often than chance would predict.¹⁸ Both involve altered muscle control during sleep, though the exact shared pathways remain unclear.

If you grind your teeth only at night, daytime stress reduction may help indirectly by improving sleep quality, but it will not address the sleep-stage arousals that drive the grinding. If you grind only during the day, a custom mouth guard for teeth grinding worn at night offers no benefit because the behavior is not happening.

Nightguards protect teeth but don’t reduce grinding

Dentists prescribe occlusal splints (nightguards, bruxism mouth guards) as the default intervention for sleep bruxism. These devices create a barrier between upper and lower teeth, distributing bite forces and preventing enamel wear. The evidence confirms they protect teeth. The evidence also shows they do not reduce the frequency or intensity of grinding episodes.

A 2007 randomized controlled trial compared an occlusal splint to cognitive behavioral therapy (CBT) in adults with diagnosed sleep bruxism. Participants wore portable electromyography (EMG) devices to measure jaw muscle activity during sleep. The splint group showed no reduction in grinding episodes per hour compared to baseline. The CBT group showed a statistically significant reduction.⁷

A 2025 randomized clinical trial assigned 30 participants to one of three groups: occlusal splint, sleep hygiene plus progressive muscle relaxation, or no treatment. Both the splint group and the relaxation group reported reduced perceived stress, but only the relaxation group showed measurable reductions in self-reported bruxism frequency.⁸

Comparison of bruxism interventions by mechanism and evidence

The table clarifies the trade-off. A custom night guard for teeth grinding will stop tooth damage. It will not stop you from grinding. If your goal is to reduce the behavior itself (because it causes jaw pain, disrupts your partner’s sleep, or worsens headaches), you need an intervention that targets the behavior, not just its consequences.

CBT and biofeedback reduce grinding more than splints do

Cognitive behavioral therapy for bruxism focuses on stress management, sleep hygiene, and awareness of jaw tension. The 2007 RCT that compared CBT to a splint found the CBT group reduced grinding episodes by an average of 30% over six weeks, while the splint group showed no change.⁷

Biofeedback takes a different approach. A biofeedback device detects jaw muscle contractions and delivers a sensory signal (vibration, sound, or electrical pulse) to alert the sleeper. Over repeated nights, the brain learns to associate grinding with the unpleasant stimulus and suppresses the behavior.

A 2020 randomized controlled trial tested a full-occlusion biofeedback splint against a standard splint in 52 participants with sleep bruxism and temporomandibular disorder (TMD) pain. The biofeedback splint delivered a mild vibratory pulse when it detected sustained clenching. After six months, the biofeedback group showed a 40% reduction in grinding episodes per night and a significant reduction in TMD pain. The standard splint group showed no change in grinding frequency and only modest pain reduction.⁹

Daytime biofeedback training also shows promise. A 2015 study trained participants to use portable EMG biofeedback devices during waking hours to recognize and interrupt jaw clenching. The training reduced daytime clenching immediately. Six months later, participants also reported reduced nighttime grinding, suggesting that conscious control during the day can generalize to unconscious sleep behavior.¹⁰

A 2025 randomized clinical trial directly compared botulinum toxin injections to biofeedback therapy for awake bruxism. Both groups improved, but the biofeedback group showed larger reductions in self-reported clenching and jaw pain at three-month follow-up.¹¹

Biofeedback requires active participation and sustained use. A standard splint is passive. The evidence shows passive protection is not sufficient to change the behavior.

Botox injections: what the placebo-controlled trials found

Botulinum toxin type A (Botox) injections into the masseter muscles (the primary jaw-closing muscles) have been proposed as a treatment for bruxism. The toxin temporarily paralyzes the muscle, reducing the force of contractions. Two recent systematic reviews summarize the evidence.¹²¹³

Two placebo-controlled, double-blind randomized trials provide the highest-quality evidence. A 2018 trial enrolled 22 adults with sleep bruxism confirmed by polysomnography. Participants received either botulinum toxin or saline placebo injections into the masseter muscles. At eight weeks, the toxin group showed a statistically significant reduction in grinding episodes per hour compared to placebo (mean reduction of 5.8 episodes per hour in the toxin group versus 0.9 in placebo).¹⁴

A 2020 trial in South Korea tested the same intervention in 24 participants. The primary outcome was EMG-measured muscle activity during sleep. The toxin group showed reduced muscle activity at four weeks, but the difference compared to placebo was not statistically significant at the study’s predetermined threshold.¹⁵

The 2025 overview concluded that botulinum toxin reduces the force and frequency of grinding in some studies but not all, and the effect is temporary (three to six months).¹² The injections carry a cost of several hundred dollars per session and require repeat treatments. Side effects are usually mild (temporary difficulty chewing, facial asymmetry) but can include more serious complications if the toxin diffuses beyond the injection site.

Botox is an option for people with severe bruxism who have not responded to splints or behavioral interventions. It is not a first-line treatment.

Mandibular advancement devices reduce bruxism in RCTs

Mandibular advancement devices (MADs) are oral appliances that hold the lower jaw in a forward position during sleep. They are FDA-cleared for obstructive sleep apnea and snoring. Two controlled trials tested whether they also reduce sleep bruxism.

A 2009 crossover trial enrolled 10 participants with moderate to severe sleep bruxism. Each participant used an adjustable MAD, a non-adjustable MAD, and no device (control) in random order, each for one week. Polysomnography and EMG recorded grinding episodes. Both MAD conditions reduced grinding episodes per hour by approximately 50% compared to the control night. The adjustable device performed slightly better than the fixed device but the difference was small.¹⁶

A 2006 experimental trial tested a similar device in 12 participants. The MAD reduced grinding episodes by 60% on average compared to baseline. The reduction persisted across multiple nights of use.¹⁷

The mechanism is not fully understood. Advancing the mandible changes the resting length of the jaw muscles, which may reduce the likelihood of sustained contractions. MADs also open the airway, which may reduce sleep-stage arousals (a known trigger for bruxism).

MADs require professional fitting and titration. Over-the-counter boil-and-bite devices do not provide the same controlled jaw positioning and have not been tested for bruxism. Side effects include temporary jaw discomfort, excessive salivation, and tooth movement with prolonged use. MADs are contraindicated in people with severe TMD or limited jaw mobility.

If you have both snoring and bruxism, a mandibular advancement device addresses both. If you have bruxism alone, the evidence supports MADs as a behavioral intervention (reduces grinding) rather than a protective device (prevents damage).

How long does bruxism last without treatment?

How long does bruxism last? The natural history varies widely. Some people grind their teeth for a few months during a period of acute stress and then stop. Others grind for years or decades.

No large longitudinal studies have tracked untreated bruxism over time in adults. The available data come from smaller cohort studies and clinical observations. These suggest that sleep bruxism tends to be chronic when it persists beyond one year. Spontaneous remission is uncommon in adults.

Awake bruxism shows more variability. If the behavior is tied to a specific stressor (a demanding job, a life transition), it often resolves when the stressor resolves. If it has become a deeply ingrained habit, it tends to persist without intervention.

The consequences of untreated bruxism are dose-dependent. Mild, occasional grinding may cause no detectable harm. Moderate to severe grinding (multiple episodes per night, high bite force) accelerates tooth wear, increases the risk of tooth fractures, and contributes to TMD pain and headaches. A custom night guard for teeth grinding mitigates tooth damage but does not change the behavior itself, so jaw pain and muscle fatigue may persist.

The evidence reviewed here suggests that behavioral interventions (CBT, biofeedback, mandibular advancement devices) reduce grinding frequency more effectively than passive splints. If your bruxism is causing pain or disrupting sleep, these interventions offer a path to reducing the behavior, not just protecting against it.