Under terms established in 2013 by the American Psychiatric Association, substance use disorder is the umbrella diagnosis used to identify all cases of substance addiction and impairing substance abuse. People affected by serious substance problems make up a large percentage of those individuals diagnosed with the mental health condition called borderline personality disorder. In a study scheduled for publication in 2014 in the journal Addiction, a multinational research team looked at the genetic factors that might help explain the overlap between substance use disorder and borderline personality disorder. Specifically, the researchers looked at the potential impact of genetically inherited differences in basic personality traits.
People with borderline personality disorder typically have problems that include erratic patterns of thought and emotion, involvement in unpredictable and potentially dangerous behavior and unusual difficulty maintaining lasting relationships. Severely affected individuals may also experience brief periods of psychosis similar to the mental states found in people with schizophrenia (a fact that gives the condition its essentially inaccurate name). Data reported by the National Institute of Mental Health indicates that between 1 percent and 2 percent of American adults are affected by borderline personality disorder. As a rule, doctors don’t officially diagnose the condition (or any other personality disorder) in teenagers or children.
At least half of all people with borderline personality disorder have diagnosable problems with substance abuse or substance addiction; the true figure may be as high as 70 percent. In many cases, the substance in question is alcohol. However, other substances (including opioids and cocaine) are also the main source of problems in substantial numbers of affected individuals. Substance use disorder and borderline personality disorder are likely comorbid conditions. This means that the presence of both conditions probably produces a greater negative impact than either condition would typically produce on its own.
Personality traits are the basic behavioral attributes that help define adults and distinguish them from one another. Teenagers and younger children also have these traits, although they aren’t usually as permanent or fixed. Generally speaking, five basic traits interact to create the adult human personality. Psychologists typically label these traits as agreeableness, conscientiousness, openness, neuroticism and extraversion or outward focus. Any given individual has his or her own specific blend of these traits, and this blend helps determine his or her basic orientation toward the self and toward the world. Part of each individual’s mixture of personal attributes is apparently passed on through genetic inheritance, although life experiences also play a primary formative role.
In the study slated for publication in Addiction, researchers from the U.S., Australia and the United Kingdom used an examination of 3,127 Australian adults to assess the impact of any overlapping genetic factors that increase the odds of developing substance use disorder and borderline personality disorder. All of the people participating in the study were twins; since twins have the same genetic profiles, they’re commonly used to help researchers separate inherited risks for a condition from environmental risks. The researchers used phone interviews to identify cases of substance use disorder related to the consumption of alcohol, marijuana/cannabis or nicotine. They used questionnaires to identify symptoms of borderline personality disorder, as well as each participant’s mixture of the five basic personality traits.
The researchers concluded that genetic inheritance accounted for approximately half (49 percent) of the risk of developing borderline personality characteristics, as well as roughly 38 percent to 42 percent of each participant’s likelihood of having specific personality traits. They also concluded that genetic inheritance accounted for a minimum of 47 percent and a maximum of 78 percent of the odds of developing diagnosable nicotine, cannabis or alcohol problems. In addition, the researchers concluded that genetically inherited personality traits account for at least some of the overlap between borderline personality characteristics and diagnosable problems with cannabis consumption and alcohol consumption. Specifically, the trait called extraversion (which features “positive” characteristics such as warmth and assertiveness) was mildly linked to cannabis problems and borderline personality. The trait called neuroticism (which features “negative” characteristics such as oversensitivity and anxiousness) was quite strongly linked to alcohol problems and borderline personality.
Based on their findings, the study’s authors believe that genetic variation in the baseline traits common to all human beings (especially neuroticism) helps explain why substance use disorder and borderline personality disorder appear together with such frequency. However, they also note that non-genetic environmental factors also play an important part in explaining this link.