According to the Centers for Disease Control and Prevention, suicide is the 10th leading cause of mortality in the United States, with rates of suicide rising over the past 2 decades. In 2016, completed suicides accounted for approximately 45,000 deaths in the United States (). While progress has been made to lower mortality rates of other leading causes of death, very little progress has been made on reducing the rates of suicide. The term “suicide,” as referred to in this article, encompasses suicidal ideation, suicidal behavior, and suicide death.
Researchers have been investigating potential risk factors and prevention strategies for suicide. The relationship between suicide and sleep disturbances, specifically insomnia and nightmares, has been well documented in the literature. Given that insomnia and nightmares are potentially modifiable risk factors, it continues to be an area of active exploration for suicide rate reduction. While there are many different types of sleep disorders, including excessive daytime sleepiness, parasomnias, obstructive sleep apnea, and restless legs syndrome, this article will focus on the relationship between insomnia and nightmares with suicide.
Insomnia disorder, according to the American Psychiatric Association’s DSM-5, is a dissatisfaction of sleep quantity or quality that occurs at least three nights per week for a minimum of 3 months despite adequate opportunity for sleep. This may present as difficulty with falling asleep, staying asleep, or early morning awakenings. The sleep disturbance results in functional impairment or significant distress in at least one area of life (American Psychiatric Association. Arlington, Virginia: APA; 2013). While insomnia is often a symptom of many psychiatric disorders, research has shown that insomnia is an independent risk factor for suicide, even when controlling for mental illness. Studies have shown that there is up to a 2.4 relative risk of suicide death with insomnia after adjusting for depression severity ().
Nightmares, as defined by the American Psychiatric Association’s DSM-5, are “typically lengthy, elaborate, story-like sequences of dream imagery that seem real and incite anxiety, fear, or other dysphoric emotions” (American Psychiatric Association. Arlington, Virginia: APA; 2013). They are common symptoms in posttraumatic stress disorder (PTSD), with up to 90% of individuals with PTSD experiencing nightmares following a traumatic event (). Nightmares have also been shown to be an independent risk factor for suicide when controlling for mental illness. Studies have shown that nightmares are associated with an elevated risk factor of 1.5 to 3 times for suicidal ideation and 3 to 4 times for suicide attempts. The data suggest that nightmares may be a stronger risk factor for suicide than insomnia ().
The mechanism linking insomnia and nightmares with suicide has been theorized and studied by researchers. A couple of the most noteworthy proposed psychological mechanisms involve dysfunctional beliefs and attitudes about sleep, as well as deficits in problem solving capability. Dysfunctional beliefs and attitudes about sleep (DBAS) are negative cognitions pertaining to sleep, and they have been shown to be related to the intensity of suicidal ideations. Many of the DBAS are pessimistic thoughts that contain a “hopelessness flavor” to them, which lead to the perpetuation of insomnia. Hopelessness has been found to be a strong risk factor for suicide. In addition to DBAS, insomnia has also shown to lead to impairments in complex problem solving. The lack of problem solving skills in these patients may lead to fewer quantity and quality of solutions during stressful situations and leave suicide as the perceived best or only option.
The biological theories focus on serotonin and hyperarousal mediated by the hypothalamic-pituitary-adrenal (HPA) axis. Serotonin is a neurotransmitter that is involved in the induction and maintenance of sleep. Of interesting note, low levels of serotonin’s main metabolite, 5-hydroxyindoleacetic acid (5-HIAA) have been found in the cerebrospinal fluid of suicide victims. Evidence has also shown that sleep and the HPA axis are closely related. The HPA axis is activated by stress leading to a cascade of hormones that can cause susceptibility of hyperarousal, REM alterations, and suicide. Hyperarousal, shared in context with PTSD and insomnia, can lead to hyperactivation of the noradrenergic systems in the medial prefrontal cortex, which can lead to decrease in executive decision making ().