Shared genetics explain the link between borderline personality and cannabis use, but not alcohol | Research

The takeaway

In over 5,600 twins, the association between borderline personality traits and cannabis use was explained by shared genetic factors, while the link with heavy alcohol use was driven by environmental factors.

Read this if you want to understand why certain personality traits and substance use tend to occur together.

Cannabis-BPT link: genetic. Alcohol-BPT link: environmental.

What the researchers found

Researchers studied 5,638 Dutch and Belgian twins aged 21-50 from 3,567 families. Significant associations were found between borderline personality traits (BPT) and high alcohol consumption (r=0.192), regular smoking (r=0.299), and ever using cannabis (r=0.254).

Bivariate genetic analyses revealed different etiologies for each association. The correlations between BPT and both regular smoking and cannabis use were explained by common genetic factors, meaning the same genes that increase borderline traits also increase the likelihood of using these substances.

For heavy alcohol consumption, the story was different: the association with BPT was explained by unique environmental factors rather than shared genetics. This meant that the alcohol-BPT connection arose from life experiences that influence both traits, not from an underlying genetic vulnerability.

Why it matters

Understanding whether substance use in borderline personality is genetically driven or environmentally driven changes the treatment approach. Genetic overlap suggests shared neurobiology; environmental overlap suggests addressing life circumstances and coping strategies.

The numbers in context

5,638 twins, 3,567 families. BPT-alcohol correlation: r=0.192 (environmental). BPT-smoking: r=0.299 (genetic). BPT-cannabis: r=0.254 (genetic).

How the study worked

Twin study with 5,638 participants from 3,567 families. Bivariate genetic modeling decomposed the associations between borderline personality traits and substance use into genetic versus environmental components.

What this study cannot tell us

Twin studies assume equal environments for identical and fraternal twins, which may not perfectly hold. Self-reported substance use and personality traits. "Ever use of cannabis" is a crude measure that does not capture frequency or problems. Dutch/Belgian population may not generalize.

How to read the evidence

Large twin study with robust genetic modeling. Strong design for decomposing genetic vs environmental contributions, though limited by self-report measures.

When this study was published

Published in 2012. Gene-trait association studies have become more sophisticated with genome-wide approaches.

The bigger picture

This study challenged the assumption that all substance use in borderline personality has the same cause. The finding that cannabis and smoking share genetic roots with BPT while alcohol does not suggests different therapeutic targets for different substance patterns.

Questions still open

Which specific genes are shared between BPT and cannabis use? Would identifying these shared genes improve treatment? Does the genetic overlap explain why borderline patients find cannabis subjectively helpful?

Common questions

Why do people with borderline traits use more cannabis?

This study found the connection is largely genetic: the same genes that contribute to borderline personality traits also increase the likelihood of cannabis use. This suggests a shared neurobiological vulnerability rather than cannabis use being simply a coping mechanism.

Is the alcohol connection different?

Yes. Unlike cannabis, the link between borderline traits and heavy alcohol use was driven by environmental factors, not genetics. This means life experiences that promote both traits (like trauma, social environment, or stress) explain the alcohol connection.

Read the original research

Borderline personality traits and substance use: genetic factors underlie the association with smoking and ever use of cannabis, but not with high alcohol consumption.

Journal of personality disorders, 26(6), 867-79

View on PubMed ↗Publisher’s paper ↗

Citation

Distel, Marijn A; Trull, Tim J; de Moor, Marleen M H; Vink, Jacqueline M; Geels, Lot M; van Beek, Jenny H D A; Bartels, Meike; Willemsen, Gonneke; Thiery, Evert; Derom, Catherine A; Neale, Michael C; Boomsma, Dorret I. (2012). Borderline personality traits and substance use: genetic factors underlie the association with smoking and ever use of cannabis, but not with high alcohol consumption.. Journal of personality disorders, 26(6), 867-79. https://doi.org/10.1521/pedi.2012.26.6.867