Born to Booze? The Neurological roots of Alcoholism

Introduction

The scientific debate over alcoholism leaves people divided. As you may expect, there is significant evidence proving that environmental and social factors encountered throughout a person’s lifetime play a huge role in one’s risk of developing Alcoholism Use Disorder (AUD). Contrary to popular belief, there is also significant evidence to prove that genetics may provide a predisposition to AUD which will be discussed in this article. Investigations so far (primarily involving monozygotic and dizygotic twins) have found that the risk of developing AUD is 50-60% related to your genetics and 40-50% related to psychosocial factors.

The Dopamine Dilemma

Dopamine is a crucial neurotransmitter in understanding addiction. Dopamine is the “chemical messenger” giving you that “feel good feeling” when petting a dog, hearing your favourite song, receiving a compliment or parallel parking on the first try, however substance abuse elicits this same chemical response. When consumed, alcohol activates certain opioid receptors concentrated in a group of subcortical nuclei (responsible in the brain for executive function and emotional behaviors). When these opioid receptors are stimulated, dopamine is released, forming an association between alcohol and reward. When an individual then encounters a cue that predicts reward, previously enforced by that alcoholdopamine association, a psychological mechanism called “Incentive Salience” is triggered which contributes to abusive alcohol consumption. Now that you have a brief understanding of how the brain’s reward system responds to alcohol, we can delve into what exactly a genetic predisposition to alcohol entails.

DRD2: The gene that makes happy hour too happy

The gene encoding for the dopamine D2 receptor (the 2nd of the 5 dopamine receptor subtypes) is called DRD2, associated with increased alcohol consumption, through methods involving incentive salience. But why does this vary between individuals? We all possess the DRD2 gene but the nucleotides it is composed of vary. A single nucleotide polymorphism (SNP) is a genetic variation at a single position in the DNA sequence. If an SNP occurs within DRD2, its genetic sequence changes and the Dopamine receptor’s structure and function may be altered, affecting its behavior. A preliminary study investigating how specific SNPs are related to alcoholism was conducted by the National Drug Dependence Treatment Centre (NDDTC) in New Delhi and documented at the BMC Medical Genetics journal. The study involved 90 alcoholics and 60 unrelated, age-matched control subjects; DNA was collected from each participant and then genotyping techniques were used to extract the variation in the DRD2 gene in each individual. The identified SNPs were then compared between alcohol dependent and control subjects. They found a strong link between the –141Cins allele and alcohol dependance and a possible link between the TaqlA1 allele (a polymorphism located within the DRD2 gene) and AUD. The combination of both alleles present in an individual increased risk of developing AUD by 250%. Not only this, TaqlA1 is a variant of an SNP associated with lower dopamine reception- leading to weaker dopamine signaling in response to reward stimuli, increasing susceptibility to alcohol dependency as people may seek stronger stimuli to compensate.

Can you undo that genetic cocktail you were born with?

SNP, the conversation.com

In short, no you cannot. In terms of genetic inheritance, SNPs are passed down from parents to children, just like height or eye colour causing a genetic predisposition to AUD. Interestingly, some SNPs once provided an advantage like disease resistance and therefore persist in populations. But blaming evolution for your drinking habits? Darwin would like a word. These evolutionary differences mean genes related to AUD vary within cultures. The experiment conducted by the NDDTC only involved participants of Indian descent making their results unapplicable to all regions. In fact, other experiments documented that showed positive results for European or European American populations but generally negative findings for studies conducted with a Taiwanese population.

Conclusion

comparison between alcohol-dependant patients and control subjects, Longdom Publishing SL

While Psychosocial factors undeniably influence alcohol consumption, the correlation between genetics and AUD cannot be ignored. Research into the DRD2 gene and relevant SNPs highlights how genetic variations can impact dopamine signaling and subsequently AUD. Understanding the neurological and genetic underpinnings is crucial for prevention and treatment of alcohol abuse. Though we cannot currently change the genetic “cocktail” we are born with, developing genetic engineering technology may make that possible in the near future, allowing for personalised interventions to mitigate the risks associated with genetic predispositions. But generally, an understanding of both the genetic and environmental factors will allow an individual to make informed decisions relating to alcohol consumption. So no, you cannot entirely blame your ancestors for your hangover, though they may have passed down the love for “just one more”.