Heritability of avoidant and dependent personality disorder traits

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.

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

add to favorites email to friend print save as pdf

Related Stories

The dark path to antisocial personality disorder

Feb 07, 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 ...

Study looks more closely at personality disorders

Sep 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 ...

Personality disorders cause emotional reactions in staff

Apr 10, 2008

A study published today in the open access journal BMC Psychiatry suggests that the way in which professional care workers respond emotionally to substance abuse patients with personality disorders depends on the type of dis ...

Recommended for you

Mindfulness helps teens cope with stress, anxiety

3 hours ago

As the morning school bell rings and students rush through crowded corridors, teenagers in one Portland classroom settle onto mats and meditation pillows. They fall silent after the teacher taps a Tibetan ...

Study links suicide risk with insomnia, alcohol use

5 hours ago

A new study is the first to show that insomnia symptoms mediate the relationship between alcohol use and suicide risk, and that this mediation is moderated by gender. The study suggests that the targeted ...

Echolocation acts as substitute sense for blind people

12 hours ago

Recent research carried out by scientists at Heriot-Watt University has demonstrated that human echolocation operates as a viable 'sense', working in tandem with other senses to deliver information to people with visual impairment.

User 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.