The Role of Biology in Drug Addiction

Drug use is a complex behavior influenced by biological and environmental factors. Most research identifies that both factors play a role in drug addiction. However, these factors do not equally influence whether an individual is more or less susceptible to drug addiction. Individuals who are drug dependent have been found to have brain abnormalities that appear to have a genetic cause. According to Prom-Wormley, E. C., Ebejer, J., Dick, D. M., & Bowers, M. S. (2017) “There are substantial genetic influences on substance abuse that are expected to influence multiple neuro-transmission pathway”.

Adoption studies as well as twin and family studies provide support for the idea that biology is the dominant factor in drug addiction.

A typical trait of addictive personality is impulsiveness, and impulsivity is 49% genetic. In individuals who are drug users, there is a relationship between impulsiveness and brain abnormalities. Research also shows that with substance dependence, an individual’s prefrontal cortex contains irregular subcortical areas associated with impulse control, learning, and addiction.

These irregularities have been observed in non-substance dependent siblings of individuals with drug addictions. This provides evidence that the abnormalities are hereditary. It is also evident that brain irregularities exist before the start of addiction. According to Garrett and Hough (2018), “Addicts have transmitter and receptor irregularities and structural and functional anomalies that appear to be genetic in origin”.

Family and twin studies determine that substance abuse disorders are genetic. Twin studies on all occasions conclude that substance dependence is highly influenced by genetics. Neuroimaging has given new insights and further support that genetics plays the dominant role in addiction.

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In this case, brain scans display what areas are different in individuals with family history of substance abuse compared to individuals with no family history of substance dependence. “Neuroimaging twin studies of substance abuse have begun to connect knowledge regarding the role of neural networks involved in substance abuse with genetic and environmental influences on the disorder”. These studies have deduced that there are physical differences in the brain of an individual genetically predisposed to substance abuse compared to the brain of an individual with no family history of substance dependence.

The adoption study method compares the relationship between offspring reared by their biological parents and offspring reared by adoptive parents, whose biological parents have substance dependence show strong support that the genetic component of substance abuse is dominant compared to environmental components. Two studies described by Agrawal and Lynskey (2008) both found that rates of substance abuse were higher in the adopted children than in the children raised by their biological parents. Of the 78 adopted children, 18% met the criteria for substance dependence, while only two of the 55 children raised by their biological parents met the criteria for substance dependence (Agrawal & Lynskey, 2008). The adoption study method provides support that biology is the dominant factor in drug addiction.

In conclusion, various types of studies including but not limited to adoption studies, twin studies, and brain studies such as neuroimaging determine that substance abuse is heavily influenced by genetic factors compared to environmental factors. These studies do not eliminate environmental factors altogether, in fact, several of the studies concur that nurture plays a key role in substance abuse, but genetic factors are the dominant influences in substance dependence. A better understanding of genetic factors in relation to substance dependence will assist researchers in the prevention and treatment of substance abuse.