Heritability of avoidant and dependent personality disorder traits

September 24, 2012
Heritability of avoidant and dependent personality disorder traits
Credit: Colourbox

(Medical Xpress)—A new twin study from the Norwegian Institute of Public Health shows that the heritability of avoidant and dependent personality disorder traits might be higher than previously reported. People with avoidant personality disorder are often anxious in the company of others, while people with dependent personality disorder feel more secure.

Results from previous studies indicate that explain about one third of the individual differences in these personality disorder traits, while the remaining variation is best explained by environmental influences. These studies used single-occasion interviews only.

In contrast, the current study used two different measures of assessment at two different time-points in order to measure personality disorders traits, and is therefore considered more methodologically sound. In 1998, 8,045 young adult twins answered a questionnaire that included questions about personality disorder traits. Some years later, 2794 of these twins took part in a structured diagnostic interview. Both identical (monozygotic) and fraternal (dizygotic) twins participated.

share 100% of the , while fraternal twins share on average 50%—meaning that they are genetically similar to other siblings. By comparing how similar the two types of are on a particular trait, researchers can determine how much of the variation between individuals can be explained by genes and environment, respectively.

Higher heritability when controlling for random effects

The researchers found that two thirds of the variation in avoidant and dependent personality disorder traits could be explained by genes, and that the most important environmental influences were those unique to each twin. Such can be any that contribute to the twins in a pair being different, e.g. the influence of different friends, teachers, activities, or various life events.

"It is important to emphasize that the term heritability does not refer to individuals per se. Heritability is a statistic that relates to the population as a whole, and is expressed as a proportion of how much the total variation in a trait, such as personality disorders, is influenced by genes", says PhD student and first author of the study Line C. Gjerde.

"The strength of this study is that we have measured personality disorder traits with both a questionnaire and, at a later time-point, an interview. This provides a better estimate of than studies that measure personality disorder once and with one instrument only. The method applied in the current study allows us to capture the core of these personality disorder traits and not random effects, or effects specific to a certain time point or method of assessment", Gjerde explains.

Implications for clinicians

The key finding that genes are so influential in the development of personality disorders emphasizes the importance of obtaining a thorough family history from patients with symptoms of such disorders. However, this does not mean that personality disorders are not treatable. Gjerde emphasizes that the strong genetic influence found in the study does not imply any form of determinism:

"If a person has a family history of , this does not necessarily mean that he or she will develop a personality disorder. Whether or not a genetic vulnerability leads to the expression of a certain trait or disorder depends on a complex interplay of both genetic and environmental factors."
The study was carried out in collaboration with the Virginia Institute for

Psychiatric and Behavioral Genetics at the Virginia Commonwealth University.

Explore further: The dark path to antisocial personality disorder

More information: L.C. Gjerde, N. Czajkowski, E. Røysamb, R.E. Ørstavik, G.P. Knudsen, K. Østby, S. Torgersen, J. Myers, K.S. Kendler and T. Reichborn-Kjennerud (2012) The heritability of avoidant and dependent personality disorder assessed by personal interview and questionnaire. Acta Psychiatrica Scandinavica, pp.1-10. DOI: 10.1111/j.1600-0447.2012.01862.x

Related Stories

The dark path to antisocial personality disorder

February 7, 2012
With no lab tests to guide the clinician, psychiatric diagnostics is challenging and controversial. Antisocial personality disorder is defined as "a pervasive pattern of disregard for, and violation of, the rights of others ...

New approach could more effectively diagnose personality disorders

February 20, 2012
(Medical Xpress) -- Personality disorders could be more effectively diagnosed by identifying and targeting the disrupted neurobiological systems where the disorders originate, report Cornell researchers.

Study looks more closely at personality disorders

September 21, 2011
A newly published paper from Rhode Island Hospital argues against the proposed changes to redefine the number of personality disorders in the upcoming Diagnostic Statistical Manual, 5th edition (DSM-5). In their study, the ...

Men and women have major personality differences

January 4, 2012
Men and women have large differences in personality, according to a new study published Jan. 4 in the online journal PLoS ONE.

Recommended for you

High moral reasoning associated with increased activity in the human brain's reward system

August 22, 2017
Individuals who have a high level of moral reasoning show increased activity in the brain's frontostriatal reward system, both during periods of rest and while performing a sequential risk taking and decision making task ...

Wealth disparity and family income impact the brain development of female youth

August 22, 2017
Female teenagers living in neighbourhoods with wide salary gaps and a low-income household show changes to their brain maturation that could indicate a higher risk of developing mental illness in adulthood, suggests a recently ...

Yoga and meditation improve mind-body health and stress resilience

August 22, 2017
Many people report positive health effects from practicing yoga and meditation, and experience both mental and physical benefits from these practices. However, we still have much to learn about how exactly these practices ...

Brain's self-regulation in teens at risk for obesity

August 22, 2017
In a small study that scanned the brains of teenagers while exposing them to tempting "food cues," researchers report that reduced activity in the brain's "self-regulation" system may be an important early predictor of adult ...

New study rebuts the claim that antidepressants do not work

August 18, 2017
A theory that has gained considerable attention in international media, including Newsweek and the CBS broadcast 60 minutes, suggests that antidepressant drugs such as the SSRIs do not exert any actual antidepressant effect. ...

Should I stay or should I leave? Untangling what goes on when a relationship is being questioned

August 17, 2017
Knowing whether to stay in or leave a romantic relationship is often an agonizing experience and that ambivalence can have negative consequences for health and well-being.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.