Restless legs syndrome (RLS) seems to come from a mix of brain chemistry, iron metabolism, genetics, and other medical conditions, rather than one single cause.

Core medical causes

  • Dopamine imbalance in the brain: Many experts think RLS is linked to how the brain uses the chemical dopamine, which helps control muscle movement. When dopamine signaling is off, the brain may send abnormal movement or discomfort signals to the legs.
  • Iron deficiency: Low iron (even “low-normal” levels) is strongly associated with RLS and can change how the brain uses dopamine. Iron deficiency may come from blood loss, poor intake, heavy periods, frequent blood donation, or digestive bleeding.

Other health conditions that can trigger RLS

RLS often appears together with other problems, which may either cause it or make it worse:

  • Chronic kidney disease or kidney failure (often with anemia and low iron).
  • Diabetes and peripheral neuropathy (nerve damage in feet and legs).
  • Parkinson’s disease and other neurological conditions, including spinal cord injury or damage.
  • Autoimmune or inflammatory diseases like rheumatoid arthritis, Sjögren syndrome, and multiple sclerosis.
  • Varicose veins, fibromyalgia, thyroid problems (overactive or underactive), and severe lung or systemic diseases in some people.

Life factors and temporary triggers

Some causes are temporary or lifestyle-related:

  • Pregnancy: RLS can first appear or get worse during pregnancy, especially in the third trimester, and often improves after delivery.
  • Vitamin and mineral deficiencies: Low magnesium, folate, or vitamin B12 have been reported along with RLS in some patients.
  • Substances that can worsen symptoms: Alcohol, caffeine, and nicotine may trigger or aggravate RLS in susceptible people.

Certain prescription medicines can also bring on or worsen symptoms:

  • Some antidepressants (for example, tricyclics and SSRIs).
  • Some antipsychotic medicines.
  • Antihistamines and some anticonvulsants.
  • Beta‑blockers and a few blood‑pressure or vascular drugs.
  • Symptoms can also flare during withdrawal from some sedatives or antidepressants.

Genetics and “no clear cause”

  • RLS can run in families, especially when it starts before age 40, suggesting a genetic component.
  • Researchers have found gene regions linked both to RLS and to iron and dopamine pathways, but the exact mechanism is still being worked out.
  • In many people, no single cause is found; doctors then call it “primary” or idiopathic RLS, likely a mix of genetics and subtle brain/iron changes.

When to see a doctor

If you have uncomfortable urges to move your legs, especially at night or when resting, and it is affecting your sleep or daily life, it’s important to:

  • Get checked for iron levels, kidney function, diabetes, thyroid problems, and vitamin deficiencies.
  • Review your current medications and substances like caffeine or alcohol with a clinician, since changing these sometimes eases symptoms.

This is general information, not personal medical advice. If you think you may have RLS or your symptoms are getting worse, please talk with a healthcare professional for evaluation and treatment options.

TL;DR: RLS is usually linked to brain dopamine and iron problems, genetics, and other illnesses (kidney disease, diabetes, neuropathy, autoimmune issues), and can be worsened by pregnancy, low vitamins/minerals, certain medications, and substances like caffeine or alcohol.