Addiction can take many forms: drugs, alcohol, gambling, pornography, even chocolate is considered a legitimate addiction. And just as an addict’s drug of choice varies, so do the causes of addiction, both physiological and environmental.
Studies suggest that 60% of Americans will sample at least one drug in their life, and 32% will continue using throughout their lifetime. But are there certain physiological factors that make someone more likely to become dependent?
In a previous article, I identified five social and cultural contributors to the development of a substance abuse disorder; here, I will break down the five natural, physiological causes that may predispose individuals to addiction.
Although the precise link between genetics and addiction is still a topic of much debate, studies have shown that 40% to 60% of predisposition to addiction is attributed to genetics.
Though no particular gene has been identified as the “addiction gene,” individuals who suffer from addiction tend to have children who also suffer from addiction at much higher rates…The term “genetics” is very broad and encompasses genes inherited – parent to child – over generations. Though no particular gene has been identified as the “addiction gene,” individuals who suffer from addiction tend to have children who also suffer from addiction at much higher rates (25% higher on average) than children of non-addict parents.
Currently, addictionologists are conducting linkage analysis on the human genome in hopes of finding candidate genes that can be directly attributed to addiction. As it stands, our best understanding comes from correlation studies of genetics and other factors such as the comorbid diagnosis of mental illness.
Comorbid Mental Illness
Research states that among the psychological afflictions that are most frequently comorbid with addiction, Bipolar Disorder is the most common, followed by Post-Traumatic Stress Disorder (PTSD), and Major Depression Disorder.
According to the National Institute on Drug Abuse, surveys have shown that many individuals who abuse alcohol and drugs also suffer from mental illness, and vice versa. Consistently, data shows that those diagnosed with a mental disorder are at least twice as likely to also suffer from a substance abuse disorder. The presence of two coexisting disorders in a single individual is referred to as comorbidity.
However, the causal relationship between addiction and mental illness is complicated. Like the dilemma of the chicken and the egg, researchers disagree on whether substance abuse causes mental disorders, or whether mental disorders lead to substance abuse. Additionally, many who suffer from a mental illness show a propensity to “self-medicate.” However, there most likely exists much overlap in the risk factors for both substance abuse and mental disorders.
Reward System: Brain Chemistry and Neurotransmitters
In the center of the brain are two masses—one for each hemisphere—of nerve cells called the nucleus accumbens. When you eat, have sex, or partake in any activity that promotes survival, this region is flooded with a neurotransmitter called dopamine, which provides a sense of pleasure from the activity.
Individuals with naturally low levels of dopamine are susceptible to substance abuse because drugs and alcohol cause an abnormally large surge in dopamine levels, activating the pleasure response. As a substance abuser continues to take the drug, the brain will become exhausted by the surges of dopamine and begin producing less and less of its own as a result. This chemical response to the drug being repeatedly introduced into the body produces physical dependency on the drug due to the now exacerbated dopamine deficiency.
Individuals with naturally low levels of dopamine are susceptible to substance abuse because drugs and alcohol cause an abnormally large surge in dopamine levels, activating the pleasure response.
Similarly, serotonin deficiency—linked to depression, anxiety, and Obsessive-Compulsive Disorder—has recently been found to also pose risk for addiction. In particular, ethanol, cannabinoids, opioids, and psychostimulants have been used by many to “self-medicate,” raising the previously low levels of serotonin in the body at the risk of physical dependence.
Studies have shown that cellular systems and behavioral levels are converging in such a way to suggest that addiction represents pathological dysfunction of the brain’s memory processes.
Due to the consequences of our behaviors, we learn to behave in a way that will maximize future gain and success. Current studies suggest that individuals predisposed for addiction have a dysfunction with the way they learn from behaviors; in other words, it may take the individual more attempts at a behavior to fully learn of its consequences. With the introduction of substance abuse, it’s suggested that some addicts are overlearning the motivational cues associated with drug and alcohol consumption.
Though it may not seem like the most obvious physiological factor, studies are showing that there are significant differences in addiction rates between men and women. In fact, the differences are so great that the results of ongoing studies are being incorporated into new treatment techniques.
The reason women are more apt to become addicted is due to the fact that they are naturally (and socially) more prone to psychological distress, particularly mood and anxiety disorders.Worldwide, men have been found to have higher rates of addiction than women, at a ratio of about 2 to 1. However, current research has shown key differences in addiction between genders. A study presented by the American Psychological Association suggests that although women begin using substances at much smaller dosages than men, their drug use escalates into addiction much more rapidly than for men. Additionally, women face a higher chance of relapse than men. According to a study out at UCLA, the reason women are more apt to become addicted is due to the fact that they are naturally (and socially) more prone to psychological distress, particularly mood and anxiety disorders.