Which Comes First: Addiction Or Impaired Impulse Control?
Impulsivity And Addiction
Impaired impulse control often accompanies drug and alcohol addiction. The National Institute of Drug Abuse's 2010 publication Drugs, Brains and Behavior: The Science of Addiction  explains that drug addiction is responsible for decreased impulse control while at the same time increasing the addict's desire to take more drugs. This reduction of self-control happens not only to the addict but also to the casual or new user. A 1996 study "Escalated substance use: A longitudinal grouping analysis from early to middle adolescence " showed that teens who experimented with drugs or used them more often in a recreational setting were more likely to have lower levels of self-control than were their peers who did not experiment with drugs and alcohol.
This relationship between impulse control and addiction is under investigation, however, leaving researchers to ask the chicken-egg question: Which actually comes first in an addict?
Questioning The Relationship Between Impulsivity And Addiction
A new study published in Science  in 2012 set out to answer the question and looked more closely at the relationship between cocaine addiction and impaired impulse control. Researchers from the University of Cambridge conducted the study.
The scientists followed 50 pairs of siblings from England. In each pair, one person was addicted to cocaine while the other sibling had no history of drug abuse. The researchers found that in the pairs of siblings, brain scans of both individuals' brains showed different sensory mechanisms between the brain's emotional center and its control center, making it more difficult for those individuals to stop impulses that they felt. In other words, the difficulty in practicing self-control occurred in both the addicted and non-addicted individuals in the different sibling pairs. By contrast, brain scans of people who were not related showed none of the differences in the sensory mechanism.
The Significance Of The Findings
The authors claim that the outcome of their study may indicate a biological or genetic predisposition to impulsivity that may contribute to the development of addiction. The researchers hypothesize that these findings may help neurologists determine who is at elevated risk for impaired-impulse control early in their lives. By determining whether people are at risk, psychologists or other physicians may be able to teach self-control techniques and coping mechanisms, decreasing the likelihood of drug abuse and addiction and improving quality of life overall.
Although this study does not definitively answer the question as to which comes first – and obviously not all people with impaired impulse control become addicts – diagnosing these abnormal brain patterns at an early age may favilitate education and intervention that could prevent or decrease the incidence of addiction.