People with restless leg syndrome have an almost threefold higher risk of suicide, according to new research.
Doctors need to pay special attention to the mental health of patients with the torturous condition, warn scientists.
The common neurological disorder causes an irresistible urge to move - particularly at night - and is often linked with unpleasant sensations in the lower limbs.
It affects up to one in 20 adults in the UK - leading to severe sleep deprivation in many cases.
The study of almost 170,000 individuals found those with RLS (restless leg syndrome) were 2.7 times more likely to take their lives or self-harm.
Corresponding author Professor Xiang Gao, an epidemiologist at Penn State University in the US, said: "It suggests restless legs syndrome isn't just connected to physical conditions, but to mental health, as well.
"And, with RLS being under-diagnosed and suicide rates rising, this connection is going to be more and more important.
"Clinicians may want to be careful when they are screening patients both for RLS and suicide risk."
In the US suicide rates have risen by up to 30 percent since the turn of the century. In the UK, it is the single biggest killer of men under the age of 45.
Prof Gao said: "Suicide is a global health concern and is associated with multiple risk factors, including male sex, family history of suicide, childhood adversity, alcohol abuse, psychiatric disorders and sleep problems.
"Given sleep disturbance and depression are highly concurrent in individuals with RLS, it is plausible part of the elevated overall mortality risk associated with RLS may be driven by increased risk of death from suicide."
Prof Gao and colleagues said RLS affects about five percent of the US population. It may be caused low levels of the feel-good brain chemical dopamine - which also controls movement.
Some studies have linked it to high blood pressure, heart attacks and increasing mortality rates, and others to depression and suicidal thoughts.