It has been noted that while the majority of personality traits within individuals remain stable after 30 years of age, (4) longitudinal community studies using diagnoses of personality disorders have not been performed. With longitudinal data lacking, cross-sectional studies are available that may give clues as to the course of personality disorder. However, cross-sectional studies have a variety of limitations, including the possibility of a cohort effect explaining changes in prevalence in late life.
Antisocial personality disorder may be used as an example. The ECA study revealed that antisocial personality disorder declined from a 1-month prevalence of 0.9 per cent for individuals between 25 and 44 years of age to 0 per cent for those over the age of 65. When considering men only, the rate fell from 1.5 per cent in those aged 22 to 44 to 0.1 per cent in those over 65. (2,9 Supporting this decline in antisocial personality disorder with ageing is a study revealing the decline in lifetime prevalence in antisocial personality disorder from between 2.1 and 3.3 per cent to between 0.2 and 0.8 per cent in those aged 65 and older. (21) In addition, antisocial traits, as measured by the Minnesota Multiphasic Personality Index, reveal a decline with ageing. (22> Similarly, a study in a forensic psychiatric centre revealed that, although antisocial personality disorder declined after the age of 27, one-third remained criminally active throughout their lives. There have been several hypotheses to explain this apparent decline in antisocial personality disorder with ageing. Personality may continue to mature and develop, with symptoms improving or 'burning out' in some individuals. Others have pointed to early death due to high-risk behaviour or a change in antisocial behaviours to other symptoms including hyperchondriasis, depression, or alcoholism.(23) It may also be that behaviours such as criminality may decrease in older individuals, but that antisocial personality traits remain and are simply more difficult to measure using current diagnostic criteria. Finally, neurological changes associated with ageing may also explain a decline. A decrease in impulsive and aggressive behaviours may correlate with full myelination of frontal, temporal, and parietal cortices that does not occur until 30 or 40 years of age/2:4 As well, changes in brain neurochemistry with ageing, including serotonin and dopamine, may also result in decreased impulsiveness or aggressiveness/1^ Decreased testosterone levels in men associated with ageing may also contribute to a decline in these traits. (25)
In addition to antisocial behaviours, other cluster B personality disorders may decline with ageing. The ECA study previously reviewed found a decline in antisocial and histrionic disorder. Another community study supported a decline in histrionic personality disorder with ageing. (26) Interestingly, the pattern of decline varied with gender, with rates remaining constant in women but declining in men. Similarly, a diagnosis of borderline personality disorder is rare in elderly individuals, with only two case reports in the literature/5.) However, no study to date supports a decline in cluster A or C diagnoses. A study of schizotypal personality disorder revealed all cases began before 40 years of age and continued lifelong. (2Z>
Some preliminary work has been done on the interaction of personality disorder with Axis I diagnoses. Although some have suggested avoidant and dependent traits may predispose to or cause chronicity in elderly depression, (!8) this has not been supported by all studies.(15) In the ECA study, certain Axis I diagnoses were found to be more common with a personality disorder diagnosis. For example, all cases of obsessive-compulsive disorder in older individuals occurred concurrent with a personality disorder/13 Both generalized anxiety disorder and substance use disorders were more common in the presence of a personality disorder in older individuals. There were no differences in the prevalence of schizophrenia and major depression in those with or without a personality disorder. The findings need to be confirmed since the group of elderly with personality disorders was small.
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