The 5-HTTLPR gene is a polymorphism in the serotonin transporter gene (SLC6A4). It has two primary alleles: the long allele (L) and the short allele (S). These variants have been associated with different personality profiles (Steiger, 2004):

- The long allele is linked to over-control, compulsiveness, and perfectionism.

- The short allele is associated with impulsivity, emotional reactivity, and mood instability—traits commonly observed in individuals with borderline personality disorder and certain eating disorders. 

This finding supports the idea that these disorders may lie on a shared neurobiological spectrum, influenced by both genes and life experiences.

Saint Olaf College

Both genetic and environmental factors shape personality. Twin studies suggest that approximately 40–60% of personality trait variation is heritable (Power et al., 2015). However, these findings can be influenced by shared environmental conditions in twin rearing.

Power et al. (2015) also found that neuroticism and openness are more strongly inherited within families than traits like extraversion, agreeableness, or conscientiousness. This is notable for research on Borderline Personality Disorder (BPD) and eating disorders (EDs), as neuroticism—characterized by emotional instability, anxiety, and perfectionism—is a shared trait in both.

Heritability of Personality Traits in both BPD and ED

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Bozzatello, P., Garbarini, C., Rocca, P., & Bellino, S. (2021). Borderline Personality Disorder: Risk Factors and Early Detection. Diagnostics (Basel, Switzerland), 11(11), 2142. https://doi.org/10.3390/diagnostics11112142
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Dyson Tori, Thomas Susan J., Townsend Michelle L., Finch Adam, South Alexandra, Barkus Emma, Walter Emma, Mendonca Carley, Grenyer Brin F. S., Pickard Judy A. (2023). Salivary testosterone and cortisol levels in borderline personality disorder before and after a 12-week group dialectical behavior therapy intervention. Frontiers in Psychology, 14(14). https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2023.1195187

Federici, A. (2009). Dialectical Behaviour Therapy for the Treatment of Eating Disorders. NEDIC, NEDIC Eating Disorders Bulletin.

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Lee, S. S. M., Keng, S.-L., & Hong, R. Y. (2024). Validating the biosocial model of borderline personality disorder: Findings from a longitudinal study. Development and Psychopathology, 36(4), 1752–1762. doi:10.1017/S0954579423001116

Lester, R. J. (2009). Brokering Authenticity: Borderline Personality Disorder and the Ethics of Care in an American Eating Disorder Clinic. Current Anthropology, 50(3), 281–302. https://doi.org/10.1086/598782

Miller, A. E., Hotte-Meunier, A., Bain, T., Macdonald, E. P., Steiger, H., & Racine, S. E. (2025). A Qualitative Study of the Lived Treatment Experiences of Women With an Eating Disorder and Comorbid Borderline Personality Disorder. The International journal of eating disorders, 58(5), 860–867. https://doi.org/10.1002/eat.24390

Navarro-Haro, M. V., Botella, C., Guillen, V., Moliner, R., Marco, H., Jorquera, M., Baños, R., & Garcia-Palacios, A. (2018). Dialectical Behavior Therapy in the Treatment of Borderline Personality Disorder and Eating Disorders Comorbidity: A Pilot Study in a Naturalistic Setting. Cognitive Therapy and Research, 42(5), 636–649. https://doi.org/10.1007/s10608-018-9906-9

Newton, J. R. (2019). Borderline personality disorder and eating disorders: a trans-diagnostic approach to unravelling diagnostic complexity. Australasian Psychiatry : Bulletin of the Royal Australian and New Zealand College of Psychiatrists, 27(6), 556–558. https://doi.org/10.1177/1039856219852297

Ni, X., Chan, D., Chan, K., McMain, S., & Kennedy, J. L. (2009). Serotonin genes and gene–gene interactions in borderline personality disorder in a matched case-control study. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 33(1), 128–133. https://doi.org/10.1016/j.pnpbp.2008.10.022.

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Sansone, R. A., & Sansone, L. A. (2007). Childhood Trauma, Borderline Personality, and Eating Disorders: A Developmental Cascade. Eating Disorders, 15(4), 333–346. https://doi.org/10.1080/10640260701454345

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Steiger, H. (2004). Eating disorders and the serotonin connection: state, trait, and developmental effects. Journal of psychiatry & neuroscience: JPN, 29(1), 20–29.

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Reference List: Comorbidity of Borderline Personality Disorder and Eating Disorders

Neuroticism is a personality trait characterized by emotional instability, anxiety, moodiness, and perfectionistic tendencies. High levels of neuroticism have been linked to increased vulnerability for several psychiatric conditions, including [[Borderline Personality Disorder]] and various forms of [[Eating Disorders]].

Because neuroticism tends to be moderately heritable (Power et al., 2015), individuals with a family history of this trait may be at higher risk. In both BPD and EDs, neuroticism contributes to difficulties in emotion regulation, impulsivity, and negative self-evaluation.

Neuroticism in Both BPD and ED

5-HTTLPR and Personality Traits in BPD and ED

There is growing evidence that Borderline Personality Disorder (BPD) and eating disorders (EDs) share common genetic and neurobiological vulnerabilities. Both disorders are frequently associated with neuroticism, impulsivity, and emotion dysregulation.

One shared risk factor involves variants of the serotonin transporter gene (5‑HTTLPR). The short allele, in particular, is prevalent in individuals with BPD and in those with bulimia nervosa or binge eating disorder (Steiger, 2004; Ni et al., 2009). These gene variants influence serotonergic function, which affects behavioral traits such as mood regulation, appetite control, and impulse management.

This overlap suggests that BPD and EDs may exist along a shared neurobiological spectrum, shaped by both genetic predisposition and environmental experiences (e.g., trauma, early adversity).

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