Research studies largely support the role of a genetic vulnerability at the root of borderline personality disorder (BPD).
Research Studies Support Genetic Impact on BPD
Many clinicians have held the view that borderline personality disorder (BPD) is solely or mainly the product of environmental risks, ranging from aversive childhood experiences to organic trauma, but growing evidence supports a genetic vulnerability as well.
Several BPD core symptoms and features, including affective lability, suicidal behaviors, impulsivity and aggression, have been related to serotonergic dysfunction.
For instance, researchers (Gardner et al. 1990) found that among 17 BPD patients in a study, lower levels of CSF 5-HIAA were significantly associated with a history of genuine suicide attempts. 5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin.
In a 2011 study, researchers (Gunderson et al. 2011) studied a total of 368 probands (132 with BPD, 134 without BPD, and 102 with major depressive disorder) and 885 siblings and parents of probands. One research hypothesis was that BPD is caused in part by familial factors.
*Proband is a person serving as the starting point for the genetic study of a family.
This hypothesis was strongly supported. Their findings showed that an individual with a first-degree relative showing BPD exhibited a statistically significant 3- to 4-fold increase in risk of BPD compared with an individual without a first-degree relative with BPD.
In a comprehensive review of 59 related studies, researchers (Amad et al. 2014) conclude that the role of a genetic vulnerability at the root of BPD is largely supported, and gene-environment interactions had a high likelihood in the genesis of BPD.
How Researchers Study the Genetic Impact
The 59 studies (Amad et al. 2014) largely fall into four types of research: familial aggregation studies, twin studies, association studies, and molecular studies.
Familial aggregation studies
These studies analyze the frequency of BPD in first-degree relatives of a subject with BPD compared with the general population or first-degree relatives of healthy subjects.
Twin studies and heritability
Twin studies have been used to estimate the heritability of BPD. Heritability, defined as the proportion of observed variation that can be attributed to inherited genetic factors rather than environmental factors, can be estimated from the difference in the correlation between monozygotic (MZ) and dizygotic (DZ) twins.
*Monozygotic (MC) twins are derived from a single ovum and so are identical. Dizygotic (DZ) twins are derived from two separate ova, and so not identical.
Association studies on BPD
Association studies identify genetic variants that influence the risk of BPD. In genetic case-control studies, the frequency of alleles (or genotypes) is compared between cases and controls.
Molecular studies on gene–environment interactions
The molecular genetic studies examine gene–environment interactions in BPD. Environmental factors are serious life events such as experience of war, physical maltreatment, childhood sexual abuse, and severe accidents.
Gardner, David L., et al. “CSF Metabolites in Borderline Personality Disorder Compared with Normal Controls.” Biological Psychiatry, vol. 28, 1990, pp. 247-254.
Amad, Ali, et al. “Genetics of borderline personality disorder: Systematic review and proposal of an integrative model.” Neuroscience & Biobehavioral Reviews, vol. 40, 2014, pp. 6-19.
Gunderson, John G., et al. "Family Study of Borderline Personality Disorder and Its Sectors of Psychopathology." Archives of General Psychiatry, vol. 68, no. 7, 2011 July, pp. 753-762.