Personality Disorders
Neurotic personality risk factor for mental illnesses
Mar 3, 2005 - 6:08:38 PM

People with high levels of neuroticism are vulnerable to suffering from more than one psychiatric disorder at the same time (comorbidity), a new study has found. Comorbidity is commonly seen among psychiatric disorders. This study, published in the March issue of the British Journal of Psychiatry, set out to examine the degree to which variation in normal personality traits of neuroticism, extraversion and novelty seeking is linked to a diagnosis of eight common disorders:

* Internalising disorders
o major depression
o generalised anxiety
o panic disorders
o phobias

* Externalising disorders:
o alcohol dependence
o drug dependence
o antisocial personality disorder
o conduct disorder.

Neuroticism reflects emotional instability, vulnerability to stress and anxiety proneness, whereas extraversion measures sociability and liveliness. Novelty seeking, another personality dimension, measures exploratory excitability, impulsiveness and extravagance.

Internalising disorders, externalising disorders and personality dimensions were assessed in 7588 participants from a population-based twin registry in Virginia, USA.

It was found that higher scores for neuroticism significantly increased the risk for all the disorders examined, with the highest risk for generalised anxiety disorder and the lowest for conduct disorder.

The effect of extraversion was modest overall, with no consistent pattern across internalising and externalising disorders. Novelty seeking was most strongly associated with externalising disorders.

Internalising disorders were more prevalent in females, and externalising disorders in males. Older subjects reported a higher incidence of internalising disorders.

High novelty seeking increased the risk for externalising disorders significantly when these disorders were examined individually. It also accounted for the largest proportion of comorbidity between externalising disorders.

Somewhat surprisingly, the contribution of neuroticism to the comorbidity within externalising disorders was comparable with the effects of novelty seeking.

The most striking finding was that neuroticism, on average, accounted for 26% of the comorbidity among the other disorders in the study. This finding is consistent with previous research, and suggests that neuroticism may be a general underlying vulnerability factor for psychiatric disorder.

The authors of the study comment that the issue of psychiatric classification and an age-old question of splitting neurosis may have to be reconsidered This debate is about the classification of psychiatric disorders and contends that the current classification system that is modelled after medical model of classifying illness is artificially dividing neurotic disorders. This division is resulting in multiple psychiatric comorbidities.

Previous work from these researchers indicates that some comorbidity largely results from common genetic factors. They also found that over 50% of the genetic liability for major depression was shared with neuroticism.

Thus, the possibility of common genetic liability between personality and comorbid disorders appears to be a reasonable hypothesis, and will be the subject of further investigation.

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