Relationships of Social Anxiety and Alcohol Dependence

Abstract

In recent years many possible evolutionary explanations have been proposed for alcohol dependence. Many of these hypotheses have amassed varying degrees of support and evidence. After a brief consideration of several of these explanations this review will focus principally on the evolution of anxiety as a contributing factor to current day alcohol dependence. It is well accepted that anxiety is evolutionary conserved behavior among mammals and many other organisms that has provided improved fitness. Although high levels of anxiety may have been selected for previously, in humans high anxiety is mismatched with their current environment and social anxiety may actually cause decreased fitness. A review of the literature demonstrates that alcohol consumptions can counteract this anxiety and has thus reinfused the behavior.

Introduction

Anxiety in an evolutionary context can be defined as a trait that of physical and phycological hyperarousal for vigilance and recognition of threats. Anxiety is a fundamentally conserved behavior and has been observed widely across many species as provides increased fitness against many threats including predation and potentially harmful social situations. However, in contrast with the evolutionary environment in the current environment anxiety does provide added fitness and may in fact be harmful to the individual. Recent findings point to the idea that alcohol counteracts the harmful effects of anxiety and individuals with high anxiety are more likely to abuse alcohol and develop alcohol related diseases. While proximate causes of anxiety and alcohol abuse have well studied and evolutionary approach to this comorbidity may provide valuable insights to addressing this problem and developing future treatments and approaches.

Many Possible Mechanisms Exist

There are many evolutionary adaptations that may lead to alcohol dependence. A few of these explanations will be discussed here although the discussion is not intended to be exhaustive. One such explanation exists is found in the alcohol dehydrogenase system. The alcohol dehydrogenase is a class of enzyme responsible for processing endogenous ethanol in the metabolic processes. It has been found that the ratio of alcohol dehydrogenase aldehyde dehydrogenase to their respective substrates endogenous ethanol and acetaldehyde is key in body regulation in higher vertebrates. It was also demonstrated that his adaptation was selected for in animals more adapted to the cold found in the north(Kolosovaa2018). It was further demonstrated that the allelic variants in the alcohol dehydrogenase system for more ethanol active phenotype enzymes were a strong predicted of developing alcohol related disease or alcohol dependence later in life (Jörnvall, 1994). Suggesting that previous selection in the alcohol dehydrogenase system for better cold survival may play a role today in human populations predisposing individuals with increased metabolic rates for ethanol to alcohol dependence.

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Another possible theory is that evolutionarily conserved mechanisms of adolescents may play a role in developing alcohol dependence later in life. Linda Patia Spear explains that adolescence is a developmental period with highly conserved neurological and physical development conserved across mammalian species. Adolescents is also linked to behavioral changed including propensity to initiate alcohol consumption. Due to developing neurological system, particularly the underdeveloped GABA system, adolescents are less sensitive to the effects of alcohol (Varlinskaya & Spear, 2002). In fact, in humans and rat models adolescents are likely to consume twice as much alcohol per occasion than are adults (Substance Abuse and Mental Health Services Administration, 2008). This increased exposure to alcohol during adolescents leads to increased risk for alcohol dependence later in life. Under this theory risk alcohol dependence may simply be an artifact of the developing neural system that has been conserved among mammalian species.

A final evolutionary theory around alcohol dependence rests around a current ‘mismatch’ between the evolutionary environment and current environment. Smith et al. explain that alcohol dehydrogenase and acetaldehyde dehydrogenase are both phylogenetically ancient enzyme present even in invertebrates. These enzymes conferred evolutionary advantage allowing organism to metabolize fermented fruit even in the presence of alcohol. Selection for these enzymes was further driven by modern civilization when drinking alcoholic beverages protected against waterborne pathogens from contaminated water supplies. However, the dramatic shift in technology in modern society has created an environment with highly concentrated alcohol and no fitness advantage to its consumption. Increased alcohol metabolism may be a fitness disadvantage in the current environment (John-Smith et. Al.).

Evolutionary Importance of Anxiety

Throughout the evolutionary history of humans and their ancestors they have faces selective pressures and threats. Anxiety has been shown to be highly conserved in mammalian species and is essential to how mammals have evolved to deal with threats in their environment (Marks and Nesse, 1994). These threats to an human evolution included a wide variety of perceived dangers including physical threats such as predators violence and disease. A threat that is perhaps less often considered is social threats. Social threats could include threats to status within the group that could result in decreased access to food and resources within the group or a decreased likelihood of reproducing by lowing social status within the group. In some extreme cases ostracism from the society could have been possible (Boyer and Bergstrom, 2011). These behaviors likely creates a strong selective pressure conserving anxiety humans as in other mammals, but also creating a strong selective bias for social anxiety. It also proposes a mechanism for the prevalence of social anxiety disorder in the current population.

Synthetic Management of Anxiety through Alcohol

Anxiety is a state of hyperarousal in which the individual exhibits heightened sensed in an attempt to increase recognition of potential threats. Psychoactive drugs have a tendency to have one of two general effects on the central nervous system. Stimulants that lead to heightened sense of arousal on positive feeling and anxiolytic drugs or depressants that results in decreased state of arousal. Because anxiety is results in a heightened state of arousal alcohol and other anxiolytic drugs can result fewer perceived symptoms of anxiety (Robinson and Bolton 2013). Most drugs are consumed to obtain a desired experience. In this case alcohol consumption may be driven by the desire to decrease feeling of anxiety and uneasiness. In social setting where high anxiety may be harmful to success or cause unfavorable outcomes ‘social drinking’ may provide a fitness advantage by decreasing the tension of social situations and allowing the individual to perform more favorably. This hypothesis has been studied in controlled settings and individual with both clinically diagnosed anxiety as well as non-clinically anxious individual self-reported a reduction in anxious symptoms as a result of alcohol (Battista et al., 2010).

Epidemiological Significance

Anxiety exists in all levels within the population. Most if not all individuals feel some degree of anxiety which is still helpful in avoiding threats and dangerous situations. However, in cases of social anxiety disorder where they symptoms become clinically debilitating to the individual combating these symptoms with alcohol becomes much more likely. In fact, 13% of individuals who are diagnosed with social anxiety disorder also suffer from alcohol use disorders or chronic alcohol abuse. (Buckner et al., 2008). Such a high comorbidity between social anxiety and alcohol dependency creates a need for concern. With such a high rate of individuals using alcohol to treat anxiety social learning may begin to take place a further exacerbate the problem. A safer and healthier mechanism for managing the mismatch of anxiety the current evolutionary situation of humans needs to be considered.

Summary and Future Direction

There have been many proposed evolutionary explanations for alcohol consumption and many if not all of these theories may play some role in influencing behavior. However, the role anxiety plays in promoting alcohol consumption deserves particular attention because of its prevalence and particularly negative outcomes of individuals with both anxiety and alcohol related conditions. Better understanding the relationship between anxiety and alcohol and other substance abuse will lead to better understanding and future of treatment of both. Some future studies are needed further solidify evidence of link between social anxiety and alcohol abuse. Particularly, social anxiety has not been well studied in animal models or other species. A consistent relationship between general anxiety and alcohol consumption is consistent an animal models however little work has been to demonstrate other species exhibit social anxiety or that alcohol relieves those symptoms. The lack of evidence of social anxiety in other species does not disprove this hypothesis although more evidence of conserved phylogeny would markable strengthen the argument that this behavior is evolutionarily conserved.

References

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