Why Do Some People Use?

Drug dependence may have a genetic element but there are no guarantees

/ Author:  / Reviewed by: Chris Galloway, M.D.

(RxWiki News) Hair and eye color are easy to predict, but what about drug dependence? Why do some kids from abusive homes end up addicted to drugs and their siblings don’t?

A recent study looked at 50 sibling pairs and 50 controls to test brain function and childhood experiences.

Results found that childhood trauma could damage brain and emotional function, but did not always predict drug abuse.

"Reach out for treatment."

Karen Ersche, PhD, from the Behavioral and Clinical Neuroscience Institute at the University of Cambridge in the UK, led the investigation.

For this small study, three groups of 50 people were assessed for thinking skills, personality traits and abuse history.

The first group had a history of drug dependence, cocaine and amphetamines specifically. The second group was made up of the first group’s no-drug history, non-drug dependent siblings.

The third group was made up of unrelated controls with no history of drug dependence.

Childhood abuse was assessed for physical, sexual and emotional abuse. Most of the drug users had started using around the age of 16.

Tests found that 50 percent of the drug-dependent group, and their siblings, had parents with drug/alcohol addiction disorders.

Two factors to explain why one sibling would become drug dependent and the other would not when they were born of the same biological parents were birth order and parental divorce.

A total of 48 percent of groups one and two had divorced parents, 38 percent of the drug-dependent group was the eldest and 40 percent of the sibling group was the youngest.

Emotional, physical and sexual abuse was reported by more of the drug-dependent group than the sibling group.

Thinking skills tests included visual memory, attention span, ability to control responses to stimuli and higher thinking skills.

Scores for the higher thinking skills and the ability to control response test were higher for the healthy group compared to the sibling groups.

Trouble with impulse control, higher levels of anxiety and sensitivity to stress were all found in the sibling pairs.

Dr. Ersche said, “It has long been known that abusive experiences during childhood have long-lasting effects on behavior in adulthood and this was confirmed by our results.”

“The siblings had more troubled childhoods compared to healthy peers in the community, and we also found a direct relationship between traumatic childhoods and their personalities.”

“Not all individuals with these personality traits would have had a traumatic upbringing. Nor does everyone with these traits develop an addiction. However, our findings show that some people are particularly at risk and their upbringing may have contributed to it.”

The study did not pinpoint why some people in the same environment with the same genetic contributions develop drug-dependence and others do not.

Authors suggested in the study’s conclusion that rather than a person having genetics that encourage drug dependence maybe there were genetic factors that encourage some people to overcome traumatic events and avoid drugs.

This study was published in September in the American Journal of Psychiatry.

Funding for this study was provided by the Medical Research Council and the Wellcome Trust. No conflicts of interest were found.

Reviewed by: 
Review Date: 
September 18, 2012
Last Updated:
September 21, 2012