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Suicide

The Link Between Insomnia, Restless Legs, and Suicidal Behavior

Recent genetic analyses have uncovered a novel causal relationship.

Key points

  • Getting an adequate amount of daily sleep is critical for our emotional and physical well-being.
  • Restless leg syndrome is associated with an increased risk for depression, increase risk of suicide and self-harm, and increased mortality.
  • Insomnia is often due to restless leg syndrome; both may be modifiable risk factors for mood disorders and suicidal behavior.
  • Research found a robust association between insomnia symptoms and depression and a potentially causal effect of insomnia on suicidal behavior.

Research shows that sleep preceded the evolution of complex brains. Sleep must be very important to all animals because it justifies shutting down consciousness, closing off from the external world, reducing input from sensory systems, and risking death from predators. Getting an adequate amount of daily sleep is critical for our emotional and physical well-being. Regular difficulty falling or staying asleep is called insomnia. Twin studies have shown that insomnia is heritable. Genetic studies have identified over 200 specific genetic mutations that may underlie insomnia. Thus, it is not surprising that insomnia is so common.

Insomnia, restless leg syndrome, and suicidal behavior

Many studies have demonstrated that insomnia is associated with an increased risk for major depressive disorders, including bipolar disorder. Unfortunately, insomnia is also associated with an increased risk of suicidal ideation, suicide attempts, and suicide deaths. Currently, it is not known whether these correlations between insomnia and suicide represent a true causal relationship.

Restless leg syndrome is characterized by mostly nighttime leg restlessness that can only be relieved by movement. The symptoms often disturb sleep. Restless leg syndrome is associated with an increased risk for depression, increased risk of suicide and self-harm, and increased mortality. Twin studies suggest that restless leg syndrome is also heritable. Genetic studies have identified about 20 specific genetic mutations that are associated with restless leg syndrome.

Insomnia is often due to restless leg syndrome; both may be modifiable risk factors for mood disorders and suicidal behavior. Previous studies have reported that individuals with restless leg syndrome have a higher risk of suicide or self-harm as compared to those without restless leg syndrome. A recent study assessed for the first time whether insomnia and restless leg syndrome have a causal relationship with suicidal behavior.

Suicide has multiple risk factors, including a family history of suicide, childhood adversity, alcohol abuse, psychiatric disorders, and sleep problems. Twin studies estimate that suicidal behavior is also inheritable. Being male is also a key risk factor. For example, males, particularly older Caucasians, are nearly seven times more likely to die by firearm suicide than females.

Previously, most studies that investigated the relationships between depression, suicidal ideation, insomnia, and restless leg syndrome have been observational studies whose results are insufficient to determine a causal relationship. Recent genetic analytic methods are now capable of investigating the causal relationship between these disorders.

Surprising new research insights

A recent study assessed for the first time whether insomnia and restless leg syndrome have a causal relationship with suicidal behavior. The authors confirmed a robust association between insomnia symptoms and depression and, for the first time, demonstrated a potentially independent and causal effect of insomnia on suicidal behavior. There are many different reasons for this association. For example, insomnia may cause REM sleep dysfunction and fragmentation, which are thought to underlie depression. Alternatively, the hyperarousal state associated with insomnia may produce agitation, irritability, and hypervigilance, leading to thoughts of suicide.

The results of this study strongly encourage individuals to aggressively manage insomnia in order to prevent the development of suicidal behaviors. Furthermore, although restless leg syndrome is frequently associated with insomnia, the results of the current study did not find that it is causally related to the increased incidence of suicide. This is good news for those who suffer from this unpleasant condition.

References

Nassan M et al (2022) Genetic evidence for a potential causal relationship between insomnia symptoms and suicidal behavior: a Mendelian randomization study. Neuropsychopharmacology (2022) 47:1672–1679; https://doi.org/10.1038/s41386-022-01319-z

Zhuang S et al (2019) Association of restless legs syndrome with risk of suicide and self-harm. JAMA 2: e199966. https://doi.org/10.1001/jamanetworkopen.2019.9966

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