A persistent urge to move your body, especially when you feel like you should be able to sit still, usually points to one of several well-known medical or psychological causes. Some are straightforward, like a medication side effect or low iron levels. Others involve conditions like ADHD, anxiety disorders, or an overactive thyroid. The key to figuring out what’s behind it is paying attention to when the restlessness happens, where in your body you feel it, and whether the movement feels voluntary or completely outside your control.
Akathisia: The Inner Urge That Won’t Quit
Akathisia is a neuropsychiatric condition defined by an inability to remain still, paired with an intense inner sense of unease. People with akathisia typically feel a deep, uncomfortable restlessness concentrated in the lower body. It creates a compulsion to move: crossing and uncrossing legs, shifting weight between feet, rocking, or pacing. To someone watching, it looks like persistent fidgeting. To the person experiencing it, it feels like crawling out of their skin.
What makes akathisia distinct is that it has both a subjective and an objective layer. You feel an urgent desire to move, and you can also be observed acting on that desire in repetitive, patterned ways. The movements aren’t random or purposeless. They’re driven by that inner restlessness, and they provide only brief, partial relief before the urge builds again.
The most common trigger is medication. Antipsychotics are the classic culprit, but antidepressants (particularly SSRIs) and anti-nausea drugs can also cause it. If you recently started or changed a medication and noticed this kind of restlessness within days to weeks, that timing is an important clue. Akathisia is different from tardive dyskinesia, another movement-related side effect. In tardive dyskinesia, the movements are truly involuntary and typically involve the face, tongue, and jaw. With akathisia, you feel the urge first and then move in response to it, and the sensation is centered in the legs and trunk rather than the face.
Restless Legs Syndrome
Restless legs syndrome (RLS) shares some surface similarities with akathisia but follows a distinct pattern. The hallmark features, according to Mayo Clinic diagnostic criteria, are symptoms that start or worsen when you’re resting (sitting or lying down), improve partially or temporarily with movement like walking or stretching, and get worse at night. If your inability to stop moving hits hardest in the evening or when you’re trying to fall asleep, RLS is a strong possibility.
Iron plays a significant role. RLS occurs in roughly 30% of people with iron deficiency anemia, about five times more often than in the general population. Low iron in the blood correlates with low iron in the brain, and when serum ferritin drops below 50 mcg/L, the effects on brain iron become more unpredictable, particularly in people with a genetic predisposition. A simple blood test measuring ferritin levels is often one of the first steps in evaluating RLS. Exercise, compression devices, and acupuncture have all shown effectiveness at reducing RLS severity in controlled trials, while options like vibration pads and cryotherapy have not proven helpful for the core symptoms.
ADHD and Internalized Hyperactivity
In children, ADHD-related hyperactivity is obvious: running, climbing, constant motion. In adults, it tends to look different. The National Institute of Mental Health describes adult hyperactivity as excessive restlessness, difficulty sitting still for long periods, frequent fidgeting, and a persistent need for constant activity or stimulation. Some adults with undiagnosed ADHD describe it as a motor running inside them that they can’t turn off. They may try to do multiple things at once or gravitate toward high-stimulation activities just to feel settled.
This form of restlessness is constant rather than situational. It doesn’t worsen specifically at night like RLS, and it isn’t tied to starting a new medication like akathisia. If you’ve felt this way for most of your life and also struggle with focus, impulsivity, or organization, ADHD may be the underlying cause.
Anxiety and Psychomotor Agitation
Anxiety can push your body into overdrive in ways that feel impossible to control. Psychomotor agitation is the clinical term for this: an increase in physical activity, restlessness, and irritability that represents your nervous system over-reacting to internal or external stress. During episodes, people may pace, rub their hands repeatedly, cry, or feel unable to sit in one place. Research shows that patients with co-occurring anxiety develop agitation symptoms at moderate to severe intensity, and none of the anxious patients in a large multicentre study experienced only minor symptoms. In other words, when anxiety drives restlessness, it tends to be pronounced.
This kind of agitation also shows up in bipolar disorder during manic phases, in psychotic episodes, and in some personality disorders. The mood state during agitation can vary widely, from nervous to euphoric to angry. If your inability to stop moving comes in waves tied to emotional states, or if it’s accompanied by racing thoughts, rapid breathing, or a feeling that your body is responding to a threat you can’t identify, anxiety-related agitation is worth exploring with a mental health professional.
Hyperthyroidism and Metabolic Causes
An overactive thyroid floods your body with hormones that accelerate nearly every system. Nervousness, twitching, trembling, irritability, and a wired-but-tired feeling are classic symptoms. Tremor alone is observed in 76% of patients with an overactive thyroid. The mechanism involves an increase in the sensitivity of receptors that respond to adrenaline, essentially putting your body in a chronic state of mild fight-or-flight activation. Some patients also develop involuntary jerky movements driven by changes in how the brain processes dopamine.
Other metabolic culprits include caffeine overconsumption, stimulant use, alcohol withdrawal, and electrolyte imbalances. If your restlessness came on gradually and you’re also experiencing unexplained weight loss, a rapid heartbeat, heat sensitivity, or muscle weakness, thyroid function is worth checking through a blood test.
When Restlessness Signals Something Serious
Most causes of constant movement are treatable and not dangerous, but a few combinations of symptoms require urgent attention. If restlessness appears alongside muscle rigidity, high fever, confusion, or rapid changes in heart rate and blood pressure shortly after starting a psychiatric medication, this constellation can indicate neuroleptic malignant syndrome, a rare but life-threatening reaction. Repetitive rhythmic movements paired with loss of awareness or consciousness could signal seizure activity. Focal repetitive movements on one side of the body, especially with any change in alertness, also warrant immediate evaluation.
The distinguishing factor is whether the restlessness is accompanied by changes in your mental clarity, body temperature, or ability to control the movements at all. Pure restlessness, where you feel an urge and respond to it with voluntary movement, is uncomfortable but generally not an emergency. Movements that happen completely outside your control, paired with confusion or physical symptoms like fever, are a different situation entirely.
Sorting Out What’s Causing It
Because so many conditions share the symptom of “can’t stop moving,” the details matter. A few questions can help narrow things down:
- When did it start? Days to weeks after a new medication points toward akathisia. Lifelong restlessness suggests ADHD. Gradual onset with other physical symptoms could indicate a thyroid or metabolic issue.
- When is it worst? Evenings and rest periods suggest RLS. All-day restlessness with emotional triggers leans toward anxiety or agitation. Constant background fidgeting with no clear pattern fits ADHD.
- Where do you feel it? Deep in the legs, especially at rest, is typical of RLS. A whole-body sense of unease that demands movement points to akathisia or anxiety.
- Is the movement voluntary? If you’re choosing to move because staying still feels unbearable, that’s akathisia or RLS. If parts of your body move on their own, particularly your face or tongue, that’s a different category of movement disorder.
Tracking these patterns for even a few days gives any clinician a much clearer starting point for figuring out what’s going on and how to help.