Post-traumatic stress disorder (PTSD) is a frequent and severe disorder that can develop after exposure to a traumatic event Citation[1,2]. People with PTSD suffer from a range of symptoms that interfere with their capacities to enjoy normal life. The characteristic symptoms resulting from the exposure to a traumatic event include persistent re-experiencing of the traumatic event, persistent avoidance of stimuli associated with the trauma and numbing of general responsiveness and persistent symptoms of increased arousal. Re-experiencing symptoms consist of intrusions of the traumatic memory in the form of distressing images, nightmares or dissociative experiences, such as flashbacks. Avoidance symptoms include actively avoiding reminders of the traumatic event, including persons, places or things associated with the trauma, and more passive behaviors reflecting emotional numbing and constriction. Hyperarousal symptoms include insomnia, irritability, impaired concentration, hypervigilance and increased startle responses. In the USA, the lifetime prevalence of PTSD is 7.8%, with women (10.4%) twice as likely as men (5%) to have PTSD at some point in their lives Citation[3].
Post-traumatic stress disorder is frequently comorbid with other psychiatric disorders Citation[3,4]. According to the National Comorbidity Survey in the USA, 88% of men and 79% of women with lifetime PTSD have at least one comorbid psychiatric disorder Citation[3]. Major depressive disorder is present in 48% of men and in 49% of women with PTSD Citation[3]. It is believed that depression amplifies the effects of traumatic events, and PTSD increases vulnerability to depression Citation[4]. Among individuals who meet criteria for lifetime PTSD, 51.9% of men and 27.9% of women also have lifetime alcohol abuse or dependence Citation[3].
Multiple lines of evidence suggest an important relationship between PTSD and suicidal behavior Citation[5–8]. The association between PTSD and suicidal behavior has been observed both in clinical and in general population samples, and is irrespective of the type of trauma that led to PTSD. High rates of suicidal behavior have been found among PTSD patients exposed to combat trauma, physical or sexual abuse, intimate partner violence and natural disasters. In a nationally representative, cross-sectional study conducted in the USA, PTSD was associated with suicidal ideation and suicide attempts, with odds ratios of 2.8 (95% CI: 2.0–3.8) and 2.7 (95% CI: 1.8–3.9), respectively Citation[9]. A recent study in Denmark has shown that a registry-based diagnosis of PTSD is a risk factor for completed suicide Citation[10]. The odds ratio associating PTSD with suicide was 9.8 (95% CI: 6.7–15). The association between PTSD and completed suicide remained after controlling for psychiatric and demographic confounders (odds ratio: 5.3; 95% CI: 3.4–8.1).
Lieutenant James F Devine (Retired), former director of the New York Police Department Counseling Services, said: “PTSD is a greater cop killer than all the guns ever fired at police officers” Citation[101]. Indeed, at least 300 police officers kill themselves every year in the USA, more than are murdered by felons. Many of these suicides are committed by officers suffering from symptoms of PTSD.
Depression, alcohol abuse, personality and other psychiatric disorders in association with PTSD lead to more suicidal thoughts and behaviors compared with PTSD alone Citation[6]. Depression is associated with suicidal behavior: approximately 60% of individuals who commit suicide suffer from depression Citation[11]. Some studies suggest that the presence of comorbid depression increases the effect of PTSD on suicidality Citation[4]. At least one study has shown that depression is a mediating factor in the relationships between PTSD and suicidal behavior Citation[4]. Another study has demonstrated that persons with PTSD and depression had a greater rate of completed suicide than expected based on their independent effects Citation[10]. In Vietnam war veterans, PTSD comorbid with depression is associated with increased suicidality Citation[12], and the risk for completed suicide is nearly double among veterans with PTSD and comorbid psychiatric disorders relative to those with PTSD only Citation[13].
Considerable evidence suggests that alcohol-use disorders are associated with nonfatal and fatal suicide attempts Citation[14]. It has been observed that in individuals with substance-use disorders, comorbid PTSD increases the risk for suicidal behavior Citation[4].
In summary, available clinical and epidemiological data suggest that suicidal behavior in individuals with PTSD may be related to:
• The diagnosis of PTSD
• Comorbid depression, alcohol use disorders and/or other psychiatric disorders.
• A combination of PTSD and comorbid psychiatric disorders
Therefore, suicidal behavior in persons with PTSD may be related to:
• Neurobiological alterations associated with PTSD
• Neurobiological abnormalities associated with comorbid depression, alcohol use disorders and/or other psychiatric disorders
• Neurobiological changes associated with a combination of PTSD and comorbid psychiatric disorders
Neurobiological changes observed in PTSD include alterations in the hypothalamic–pituitary–adrenal (HPA) axis, increased noradrenergic activity, and changes in the serotonergic and other neurotransmitter systems Citation[15–17]. Pathophysiological changes in patients with PTSD also include reduced volume of the hippocampus, exaggerated amygdala responsiveness and abnormalities in prefrontal cortex function. Neurobiological abnormalities observed in depressed patients and individuals with alcohol-use disorders also include HPA axis dysregulation, serotonergic alterations and changes in the prefrontal cortex, amygdala and the hippocampus Citation[17,18]. Pathophysiological changes observed in PTSD, depression and alcoholism are different. For example, changes in the HPA axis function observed in PTSD include low basal cortisol secretion, enhanced negative feedback control of the HPA axis and increased brain corticotrophin-releasing hormone activity, while depression is associated with increased cortisol levels, reduced cortisol suppression to dexamethasone and reduced glucocorticoid receptor responsiveness Citation[17,19]. There is evidence that the activity of three neurobiological systems has a role in the pathophysiology of suicidal behavior Citation[20]. This includes both hyper- and hypo-activity of the HPA axis, dysfunction of the serotonergic system and excessive activity of the noradrenergic system Citation[20–22]. It is likely that certain biological changes, including HPA axis, serotonergic and noradrenergic abnormalities, underlie both PTSD with or without comorbid disorders and suicidal behavior.
Many people are exposed to traumatic events. However, only a minority of them fail to recover from initial reactions. Certain pretraumatic genetic, epigenetic and possibly other environmental influences increase the probability of developing PTSD following trauma exposure, and modulate biological alterations associated with its pathophysiology Citation[17]. For example, a study of combat veterans showed that the risk for developing PTSD after trauma exposure was significantly higher for monozygotic than for dizygotic noncombat exposed cotwins of PTSD-affected individuals Citation[23]. Also, maternal PTSD has been identified as a risk factor for PTSD in second-generation offspring and alterations reflecting enhanced glucocorticoid receptor responsiveness have been demonstrated in second-generation offspring with maternal PTSD Citation[17,24]. It is interesting to hypothesize that the same neurobiological factors that predispose some individuals to develop PTSD may also increase vulnerability to suicidal behavior. In other words, individuals with PTSD phenotype may have a predisposition to suicidal behavior.
Another interesting aspect is a potential role of the endocannabinoid system in the neurobiology of suicidal behavior in PTSD. The endocannabinoid system is formed by the cannabinoid receptors and endogenous ligands Citation[25,26]. The cannabinoid receptors type 1 play a role in the extinction of aversive memories, reducing fear and anxiety. The endocannabinoid system is also involved in the mechanisms of sleep regulation Citation[25–27]. For example, it has been reported that the endocannabinoid anandamide increased adenosine in the basal forebrain and increased sleep Citation[27]. Sleep abnormalities and other symptoms of PTSD may contribute to increased suicidality in PTSD patients Citation[28]. Therefore, further studies of the role of the endocannabinoid system in the pathophysiology of PTSD may help to develop new modalities to treat PTSD and suicidal behavior in persons with PTSD.
Millions of people around the world suffer from PTSD with or without comorbid psychiatric, neurological or medical conditions. Suicidal behavior in PTSD is a critical issue. Studies of the pathophysiology of suicidal behavior in PTSD may help identify targets for therapeutic drugs to treat suicidal behavior in PTSD.
Financial & competing interests disclosure
The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.
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Website
- Kates AR. PTSD: the secret cop killer www.calea.org/online/newsletter/No87/ptsd.htm