Etiology of Increased Suicide Rates at High Altitude:
A Biological Perspective
Concern is growing throughout mountain communities as studies continue to provide evidence for an increased correlation between living at high altitude and the risk for suicide. Death by suicide has increased substantially throughout the past years in all regions of the United States, but in states including Arizona, Alaska, Oregon, Utah, Montana, Idaho, Wyoming, Nevada, and Colorado, all of which have some of the highest elevations in the U.S., are reporting greatest impact. As anxiety and apprehension grow among the population in high altitude communities, researchers continue to develop theories on the cause for this relationship. Biological vulnerabilities associated with living at altitude are likely to provide clear insight to specific physiological and psychological changes in response to specific exposures seen in those only in higher elevation populations. These biological factors include physiological adaptations at ascension to elevation, hypoxia and chronic health conditions, prevalence of sleep disorders at altitude, neurological changes, mental illness, and genetic influences as they relate to general risk factors related with suicide. The research examined in this paper provides an in depth comparison of various theories related to the associations resulting from biological vulnerabilities to suicide.
Etiology of Increased Suicide Rates at High Altitude: A Biological Perspective
One topic that is creating unease across the western United States within the last few years involves studies linking high altitude to increasing suicide rates when equated the rest of the country. Although research confirms the connection between individuals living at higher elevations and death by suicide, there is a large debate about the causation behind this correlation. With the sensitivity revolving around suicide in general, and the impact it has made in elevated communities, it is imperative to find answers in order to influence the risk factors that noticeably connect suicide and those dwelling at increased elevations.
As studies have yet to determine a definitive answer as to why this relationship exists, researchers are currently looking into various theories to find the basis for this association. The majority of the data collected to explain the connection between these two variables has really only touched on social, cultural, economic, and environmental factors that are potentially influencing these populations. However, identifying the biological vulnerabilities of those residing at higher elevations exhibits the most promise in revealing the affiliation between altitude and suicide.
In the primary analysis of the associated biological processes relating risk factors to suicide, it is necessary to make assumptions regarding the overall susceptibility to suicide and principal organic changes observed at elevation. Throughout all the research previously completed concerning suicide and altitude, in addition to the risk factors associated with suicide in general, a particular vulnerability that continues to be a consistent dynamic in studies comparing high and low altitude suicides is biological motivation. The biological considerations for suicide include existing chronic illness or pain, family history related to genetics, and the overall mental health, as well as related psychological disorders. In looking from a biological perspective, the substantial physiological and psychological changes affiliated with both the initial incline and long-term residence at altitude likely play a significant role in the connection between suicide and elevation.
Suicide rates across the entire nation have gradually continued to rise since the beginning of the new millennium. According to the American Foundation for Suicide Prevention (2014), the Centers for Disease Control and Prevention (C.D.C.) reported in 2013 that suicide was the 10th leading cause of death in the United States and that approximately 42,000 suicides accounted for the number of deaths that year. Despite increased awareness and implementation of prevention programs, including enhancing access to mental health care, suicide prevention hotlines, and both state and national level resources, the overall prevalence of suicide has continued to grow. The greatest impact on the increase of suicides reported is largely affecting the higher mountain communities, specifically in the states of Alaska, Arizona, Oregon, Utah, Montana, Idaho, Wyoming, Nevada, and Colorado, all of which report some of the highest elevations in the U.S.
In Colorado alone, the effects of suicide rates hit an all-time high during this period and studies show that “in 2012, there were 1,053 suicides among Colorado residents and the age-adjusted suicide rate was 19.7/100,000. This is the highest number and rate of suicide deaths ever recorded in Colorado, and represents a 16 percent increase over the number of deaths in 2011” (Breitzman, S.A. & Hindman, J., 2013). The number reported across the entire U.S. for that same year was 12.6 per 100,000. Among the states reporting highest percentages of suicide in 2012, Wyoming (29.6%), Alaska (23.0%), Montana (22.6%), New Mexico (21.3%), and Utah (21.0%) contributed to the majority of suicides respectively. The lowest number of suicides were in the New England area and the District of Columbia reported the lowest risk at 5.7 per 100,000 (C.D.C., 2014). These states, including D.C., are located at or below sea level. Obviously, a greater emphasis and initiative to pinpoint risk factors is imperative at this point, with priority in identifying specific risk factors for all of those living at elevation.
Risk Factors for Suicide
Current statistics has clearly displayed the correlation between living at high altitude and the chance for suicide, so it is vital to understand the causes that could potentially account for the probability for an individual to commit suicide. The C.D.C. (2014) lists multiple known risk factors for suicide, including family history, mental health status, access to methods of suicide, feelings of isolation, and physical health problems, to name a few. All of these reasons can directly relate to life associated with an assortment of communities, but particularly those associated with mountain societies.
A research study by Betz and colleagues in 2011, compared the differences found for possible risks of suicide at low (<1000m), middle (1000-1999m) and high elevations (> 2000m). In their research, they found that a greater number of victims reported feelings of depression prior to the act of committing suicide at higher and middle levels of elevation when compared to individuals at lower altitude. Firearms reported to be the greatest manner used for suicides reported at all elevations. However, guns had a larger percentage of use at higher elevations (58%) than those performed at lower elevations (51%), although these percentages could be partly due to the availability of guns in these areas. What was most interesting in this study was that “middle and high altitude victims were approximately 2 and 3 times, respectively, more likely than those at low altitude to have physical health, financial, or job-related problems that contributed to the suicide” (Betz et al., 2011). Although these findings are important in showing some differences between low and high geographic communities, there are no specific implications as to the cause for this relationship, making it even more important to compare biological differences that primarily influence high altitude populations.
Biological Vulnerabilities at Altitude
The physiological effects on the human body can vary greatly when ascending to altitude, depending on the amount of time given to transition to the change in elevation and the difference in altitude occurring. The impact of adjustment directly relates to lower levels of oxygen availability in the air and the atmospheric pressure associated with being up so high. Denver, known as the Mile High City, has an altitude of 5,300 feet above sea level and the atmosphere has 20% less oxygen than cities at lower elevations and higher levels of pollution. With oxygenation being vital to all human physiological systems, the body has to exert additional energy and resources in order to acclimate to the environment. The adjustments that the body endures to compensate for the lack of oxygen are one of the main reasons that many athletes train at higher altitudes, like the U.S. Olympic Training Center in Colorado Springs, where the elevation is 6,035 feet above sea level. While there can be benefits in regulating the body to these levels, often there are hidden complexities that can arise during acclimation.
According to The Merck Manual of Diagnosis and Therapy, “most people can ascend to 5,000 to 6,500 feet (1,500 to 2,000 meters) in one day without problems, but about 20% of people who ascend to 8,000 feet (2,500 meters) and 40% who ascend to 10,000 feet (3,000 meters) develop some form of altitude disease” (West, J.B., 2014). Both the circulatory and respiratory systems feel the greatest stress, in addition to the endocrine and nervous systems, especially considering their connections to vital organs including the heart, brain, and lungs. The initial effects of increasing altitude involve symptoms including shortness of breath, dizziness, tiredness, dehydration, headaches, nausea, vomiting, and a generalized unwell feeling. A few of the diseases associated with short-term ascension include acute mountain sickness, high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE). Other problems can also occur throughout multiple structures and organs, and the symptoms may vary depending on individual response. Although physiological adaption can occur within a few days, ultimately it is impossible for an individual to become entirely acclimated to particularly high levels of elevation.
The primary cause of biological complications at altitude generally relates to a condition known as hypoxia. Hypoxia is a physical disorder involving low levels of oxygen in the tissues throughout the body. The term hypoxia often includes the condition of hypoxemia (low oxygen in the blood) as well, although medically they are separate disorders. The indications of chronic hypoxia, as experienced by those residing at altitude, include generalized muscle weakness, skin discoloration, vascular and respiratory complications, uncoordinated movements, confusion, trouble sleeping, and recurrent infections. In addition, individuals with asthma or other lung related diseases, such as Chronic Obstructive Pulmonary Disease (COPD), may experience an increase in symptoms due to altitude-related hypoxia.
Even with the biological adaptations made to compensate for long-term exposure to altitude, the body still continuously tries to adjust to lower oxygen availability. According to a review article by Valdir de Aquino Lemos and colleagues (2013), changes in the primary functioning are further complicated due to the body trying to reinstate homeostasis caused by the lack of oxygen.” Chronic exposure to altitudes between 2500 and 5000m results in sympathoadrenal responses that are exacerbated by metabolic alterations to other systems, including the immune system (de Aquino Lemos, V. et al., 2013). Cellular damage and metabolic changes create additional risk factors for chronic health problems due to increased inflammation and immune response. Lower levels of oxygen for even a few hours can result in T lymphocytes (responsible for immunity) to decrease, while natural killer cells increase exponentially. Oxygen deprivation has also led to increased changes in hormones and blood concentrations within the body, which increases likelihood for physiological and neurological complications to occur. Depending on the level and duration of hypoxia, the compensation for the lack of oxygen may result in physiological crises that can ultimately lead to detrimental effects on both the physical and mental health of an individual.
Considering that overall health is one of the leading risk factors for suicide, it is important to evaluate the connection between long-standing medical conditions that influence individuals residing at high altitude. In general, those living with chronic illness or pain are more likely to suffer on both a mental and physical threshold due to their symptoms. Reports of higher levels of depression and anxiety plague those with chronic health problems. As the quality of life and chance for improvement decreases, it creates further decline of attitude and behaviors related to their illness. The physical ailments associated with the disorder themselves can also be equally problematic in living a normal life, depending on the level of disability. Ultimately, a diagnosis of a chronic condition creates an increased vulnerability for suicide.
While the majority of life-altering, chronic conditions are not associated to any particular population, there are certain medical illnesses that are only diagnosed at high altitude. One example is Chronic Mountain Sickness (CMS), in which the body produces excessive amounts of red blood cells due to low oxygen levels in the blood. This increase of red blood cells could lead to potential blood clots within the legs, lungs, and the heart. While treatments are available, the long-term effects of this disease could create further complications following treatment. High-Altitude Pulmonary Edema (HAPE) is another condition only associated with altitude and involves the production of water particles to develop in the lungs due to the gas exchange that occurs during body regulation when oxygen levels decrease. Typically, symptoms appear shortly after ascent to altitude. However, certain individuals develop chronic sickness stemming from the onset of this condition, including respiratory difficulties and the development of cardiac arrest or failure. Other diseases, only recently identified as risk factors of high altitude residence, include High Altitude Renal Syndrome (HARS) and High Altitude Cerebral Edema (HACE), as well as systemic and pulmonary hypertension.
The frequency of chronic conditions and other health related disorders account for a large portion of deaths in high elevation communities, concurrently with suicide. According to the Colorado Department of Public of Health and Environment (2014), 50% of all Americans suffer from chronic illness, but more than 80% of all deaths in Colorado involve living with a chronic condition. The 2014 report also states that chronic diseases accounted for seven of the top 10 causes of deaths. The chronic conditions on the list consisted of high blood pressure, arthritis, asthma, kidney disease, ischemic heart disease, stroke, and COPD (Colorado Health Institute, 2014). In addition, diseases associated with living in these specific geographical locations, versus altitude, may also influence those living in mountain communities. The clinical indications of altitude related health problems could easily account for the connection of increased suicide risks among those living in mountain societies.
Given that the quality and quantity of sleep distinctly corresponds to the health and well-being of an individual, another consideration that is a principal factor for high-altitude suicide is the disruptions in sleep patterns observed at altitude. Sleep deprivation, especially when experienced over time, can cause severe physical and psychological effects, including cognitive dysfunctions, cardiovascular abnormalities, behavioral and mood disorders, and less tolerance to stress. With sleep disorders noted frequently at high altitude because of hypoxia, in addition to the relationship between lack of sleep and suicide, it is easy to relate how these factors may decipher the connection between suicide risks at altitude.
At initial ascent, travelers often report troubles associated with falling asleep or staying asleep during the night, as well as the occurrence of vivid dreams and nightmares that they are not initially predisposed to experiencing. “Recurring wakefulness is the most common characteristic due to decreased O2 saturation, which leads to sleep fragmentation. In addition, hypoxia can cause poor sleep quality due to slight reductions in delta sleep, relative reductions in REM sleep, and agitation during the night. However, overall total sleep time (TST) is not reduced” (de Aquino Lemos, V., 2014). Subsequently, hypoxia related sleep disorders, including central sleep apnea and obstructive sleep apnea, have increased dominance in those residing at altitude. This interruption in sleep behavior is likely due to the brain’s response to changes in oxygenation.
Research confirms the increased risk for suicide to various sleep disturbances due to the brain adapting to gas exchanges within the body. Lack of sleep has long been associated to higher levels of depression and inability to manage stress over time. In addition to overall behavioral and cognitive changes caused by sleep deprivation, brain chemistry is also altered when the lack of oxygen and sleep are present. Neurotransmitters, such as Dopamine and Serotonin, are critical in the acceptance of sleep and directly relate to psychological functioning. As the brain increasingly compensates for the lack of rest, the risk for suicide and other psychological disorders amplify as well.
The brain, being the central core element in the functioning of all human body systems, takes the biggest impact when experiencing changes due to high altitude hypoxia. “The mammalian brain represents 2% of the total body weight and consumes 20% of the total body oxygen for its normal function. This high level of oxygen consumption makes the brain an extremely sensitive tissue to changes in arterial blood oxygen levels” (Kumar, G.K., 2011). During initial exposure and sustained time at high elevation, changes in neurotransmitter enzymes, as well as the central and peripheral nervous systems, can increase the probability for brain injury and psychological dysfunction, in addition to other immediate health problems. These increased risks also make individuals susceptible to a higher disposition to follow through with acts of suicide.
Hypoxic effects on the brain.
It is obvious that any amount of change relating to the reduction of oxygen availability to the brain, whether from injury, illness, or altitude, can adjust regular performance in the biochemical makeup and generalized functioning of the brain itself. Multiple studies report an initial change in behavior and personality at initial ascension to altitude, as well as through chronic exposure to these elevations. Also, specific areas of the brain have increased susceptibility to changes in oxygenation, especially the “watershed” regions, which include the hippocampus, basal ganglia, cerebellum, occipital cortex and frontal regions of the brain (Bigler & Hopkins, 2001). While even short exposure to altitude can cause significant changes in the brain, the effects of serious medical issues, such as high-altitude cerebral edema (HACE), can often lead to chronic neurological disabilities.
In a study completed by Peter H. Hacket et al. (1998), researchers compared the brains of patients in Alaska and Colorado who initially presented at the hospital with HACE by using Magnetic Resonance Imaging (MRI) to compare images taken following the initial diagnosis, during recovery at the hospital, and after returning home. While gray matter in the brain stayed the same throughout all imaging on the patients, the MRI’s did provide evidence for changes in white matter that increased over time, as opposed to decreasing with the length of recovery. These findings may signify an important connection to increased suicide rates involving altitude given that the white matter of the brain is responsible for all communication transmitted within the brain structure. Lesions in white matter are responsible for many well-known neurodegenerative diseases associated with complete disability, like multiple sclerosis, and often accompany victims who have suffered extensive brain injuries that are considered irreversible. If changes in white matter can continue over time due to altitude-induced edema, then it is probable that chronic adaptations in the brain’s chemistry and functionality, as noted in various studies relating to long-term exposure at elevation, would also continue to deteriorate over time as well.
Neurotransmitters in response to altitude.
Another barrier presented by altitude-induced hypoxia in neurological processing is biochemical alterations, specifically in neurotransmitter production. Imbalances in primary neurotransmitters, such as serotonin and dopamine, contribute to the biological vulnerability of many psychological disorders relating to mood, depression and anxiety. The neurotransmitter serotonin controls individual behavior, mood, and cognitive processing. Low levels of serotonin are responsible for a variety of impulsive behaviors, including the inclination to commit suicide. In contrast, dopamine’s function is primarily to provide motivation and pleasure to balance behaviors influenced by serotonin. Similar to what’s found with low serotonin, low levels of dopamine create problems with increased depression and substance abuse disorders, also increasing the risk for suicidal behavior.
The article from Ganesh Kumar (2011) examines the impact that hypoxia has on specific neurotransmitters and the way that it affects the brain (Kumar, G., 2011). Each neurotransmitter mentioned in this article, specifically those relating to various catecholamines, have an obvious correlation between adjustments made in the brain to compensate for hypoxic effects and the severity of impact on neurotransmitter systems. “Catecholamines comprising dopamine (DA), norepinephrine (NE), and epinephrine (Epi) are expressed in many regions of the brain, adrenal medulla, and the carotid body, which is a peripheral neuronal sensory organ specialized for detecting changes in arterial blood O2” (Kumar, G., 2011). The contribution between decreasing levels of catecholamines at altitude and the extent of included neurotransmitters noted essentially may be an additional risk factor for psychological dysfunction precipitating suicide attempts of those residing at high elevation.
In addition to the adjustments of neurotransmitters and other changes that occur in the brain at altitude, alteration of behavior and the abundance of psychological disorder in western communities may add to the many biological reasons contributing to suicide rates. Numerous visitors report feelings elation and giddiness when first arriving at higher elevations as the brain adjusts to new levels of oxygen and pressure. With increased hypoxic exposure, however, changes in emotional and cognitive performance begin to decline.
Both depression and anxiety cause extensive amounts of dysfunction in physical and mental developments and are often responsible for the onset of various mood and psychological disorders. The “potential causal links between adaptation to altitude and anxiety are apparent in all three leading models of panic, namely, hyperventilation (hypoxia leads to hypocapnia), suffocation false alarms (hypoxia counteracted to some extent by hypocapnia), and cognitive misinterpretations (symptoms from hypoxia and hypocapnia interpreted as dangerous)” (Roth et al., 2002). Like anxiety, depressive disorders create further risks for suicide in states like Utah, where approximately 25% of the population has reported being depressed. In other studies, researchers were able to prove the hypothesis that changes in respiratory functions had a positive correlation to mood disorders and drug or alcohol abuse, providing science behind reports of increasing substance abuse and psychological disorders concurrent with living at elevation (Lehrer et al., 2014). The increased susceptibility to psychological disorders involving mood, anxiety, and depression for those at high altitude, as well as substance related disorders, could again explain the relationship to suicide in these areas.
According to the National Survey on Drug Use and Health (NSDUH) in February 2014, Utah showed the highest percentage for any mental illness (22.35%) across the entire United States and was the third highest for serious mental illnesses (5.14%). Other high altitude states including Washington, Oregon, and Idaho ranked among the highest percentages of individuals living with some level of mental illness. States located at or below sea level on average had less prevalence of mental illness, with New Jersey ranking the lowest at 3.97%. Additional high altitude states like Colorado, Arizona, and Wyoming fell in the middle of percentages that accounted for mental illness, with the state of Nevada being an outlier falling within the lowest bracket of mental illness. Considering other data, such as Colorado’s 2011 status report on mental illness that lists “three out of 10 (or 1.5 million) Coloradans need behavior health care” (Breitzman, S.A. & Hindman, J., 2013), further examination on specific psychological disorders need to be evaluated in order to deepen the connection between suicide and altitude within these communities.
Another primary risk factor for suicide is precedent family history of suicide and the related genetic influences behind psychological disorders. Many hereditary traits, influenced by generational adaptations and specific genes, are now linking the connection to suicidal behavior, compared to earlier familial studies that focused primarily on the nature versus nurture aspect of inheritance. What is interesting in current genetic studies is that many of the genes listed to influence suicidal tendencies are predominantly associated with neurotransmitters located within the brain. For example,” low cerebrospinal fluid concentration of the serotonin metabolite 5-hydroxyindoleacetic acid (5HIAA) has been found in numerous studies of suicidal patients, especially in high-lethality attempters” (Clement et al., 2012). Additional genetic contributions also include serotonin transporters, serotonin receptors, and dopamine receptors. By looking at the physiological differences, specifically the genetic changes over time, one can logically explain the current cause of suicide for those located at higher elevation.
As noted earlier, the body goes through tremendous stress when first ascending to altitude and physiological variations occur to increase stability of the body at higher elevations. Recent studies on genetic inheritance in response to acclimatization show that genes actually change through generations as a response to altitude adaptations. In examining the difference of Tibetans living at higher elevations along Mount Everest and the Han Chinese located below the mountain, research on physiological and genetic changes occurring within these populations now provides evidence behind the basis for the continual adaptations noted through generations. An example of one of these genetic mutations involves “Tibetans and Sherpas having lower hemoglobin concentrations at high altitude compared with Han Chinese and Westerners. These lower hemoglobin concentrations are consistent with the reduced prevalence of chronic mountain sickness in Tibetans compared with Andeans” (West, J.B., 2012). Other physiological changes include reduced cardiac abnormalities, along with higher birth weights in populations residing at higher elevation. In addition, geneticists can now list specific patterns and genes responsible for long-term adaptations linked to high-altitude, including the ESPAS1 gene that is responsible for changes associated with the hemoglobin revision. The comparison of current genetic links to suicide, along with those associated with genetic adaptations, also allows for a more balanced representation of the actual relationship between deaths by suicide within high altitude areas.
There is no doubt that there is a strong connection between residence at high altitude and the increased risk for death by suicide, especially in comparison to lower lying communities. This relationship needs further examination in all areas of research, but particularly through associating biological vulnerabilities to individual risks of living in mountain societies. When examining the psychological and physiological changes that occur in response to long-term oxygen deprivation within these high altitude populations, it is important to consider the impediments of chronic illness and neurological effects caused by hypoxia, as well as the impairments caused by sleep disorders and the abundance of mental illness. In addition, the acclimation to altitude and genetic adaptations that take place during this time also need further examination to determine probability for increased attempts of suicide.
Linking biological perspectives and identifying the foundation of this relationship can certainly improve chances for the prevention of suicide, especially when incorporated into mental health and medical education inside these communities. While social, environmental, and economic factors may be involved in the development of risks related to residing at altitude, biological vulnerabilities ultimately explain the majority of the changes associated with both the physiological and psychological complexities that are primarily present in these communities.
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