What Causes Muscle Twitches, According to Science

Sometimes, it seems like muscles have a mind of their own. Whether it’s a twitchy eyelid, a sudden spasm in your thigh or a muscle that seems to contract without cause, involuntary muscle movements are exceedingly common. (One might even be happening to you, right now, as you read this sentence.)

Most muscle twitches fall under the category of fasciculations — small, involuntary movements that can occur at random to any muscle in the body, although they’re most common in the eyelids and limbs.

No big deal, right? While admittedly annoying, these twitches are mostly harmless, and often go unnoticed. Still, while they’re rarely a sign of a neuromuscular disorder, they can sometimes signal more serious conditions. Here’s what scientists know about what causes muscle twitches and how to stop them.

If you are wondering what causes muscle twitches, there’s a good chance you’ve felt a fasciculation before. About 70 percent of healthy people have them, according to a study published in the journal Neurology in 2017. Because they’re largely benign, fasciculations haven’t been subjected to much research, and scientists still aren't sure what triggers most of them.

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Researchers know that fasciculations are likely the result of irritation within nerve cells, prompting fast, small, spontaneous and visible contractions of muscle fibers. (Some neurologists call them verminosis — from the Latin word for worm or maggot — because they look like worms moving below the surface of the skin.)

Eye twitches might be particularly common because just a small number of nerve cells supply the muscles that control our eyelids, meaning that it doesn’t require a lot of irritation to these nerve fibers to make your eyelid jerk.

While direct causes aren’t yet understood, scientists have identified a number of associations between fasciculations and other factors. Stress, for one, is a potential trigger, and fasciculations are often linked to other stress-induced symptoms like headaches, heartburn and irritable bowel syndrome.

Other possible causes include a lack of sleep, too much caffeine and even an excess of exercise. In fact, exercise is cited as one of the more common causes, according to a 2010 study in Amyotrophic Lateral Sclerosis, with twitches typically occurring after someone has completed a particularly-strenuous workout — but only in the lower leg muscles. Some over-the-counter and prescription drugs can also cause fasciculations.

Again, most twitches aren’t a cause for alarm, nor do they require medical attention. But in rare cases, they can be a symptom of illnesses or conditions that impact the central nervous system. Additionally, persistent muscle twitching may negatively affect your mental health.

Among the most concerning of these is amyotrophic lateral sclerosis, or ALS, a disease that destroys motor nerve cells — which control voluntary muscles like your biceps and hamstrings — and causes a loss of muscle function. People with ALS may lose the ability to move, eat, speak and even breathe.

It's important to note that fasciculations aren’t the only symptoms of ALS. They also tend to be accompanied by other issues like worsening muscle weakness, difficulty gripping smaller objects and trouble with talking, swallowing or walking. But because muscle twitches can still indicate severe neuromuscular issues, doctors are likely to treat them seriously.

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While most people only have occasional fasciculations, a small subset gets muscle twitches all the time — a rare condition known as benign fasciculation syndrome, or BFS.

These individuals may experience consistent, relentless twitching, which can diminish their quality of life and overall well-being. Most people with the condition experience anxiety about their symptoms, according to a 2018 study in Muscle & Nerve, and it can even contribute to depression.

There aren't really any foolproof treatments for fasciculations, which tend to resolve by themselves. However, if you have persistent muscle twitches, your doctor may want to rule out any underlying medical conditions.

One common technique for evaluating muscle twitches is electromyography, or EMG. This diagnostic test stimulates a nerve with a small electric charge and records how the muscle responds.

Some people have reduced their symptoms by taking beta-blockers or anti-seizure medications, which can lessen the excitability of certain muscles. Managing your stress — as well as your sleep schedule, magnesium levels and caffeine intake — can bring relief, as well.

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In short, if you want to know how to stop a muscle twitch, such as that pesky, twitchy eyelid, the best fix is to rest, relax and eat a magnesium-rich diet full of leafy greens and nuts. And if your fasciculations are causing your anxiety to surge, or are accompanied by other symptoms, there’s no harm in asking your doctor about them, either.