Abstract
Background
Personality disorder is now an integral part of psychiatric practice. Although no longer a ‘diagnosis of exclusion’, the place of personality disorder in clinical practice remains unclear. This thesis examines the breadth and depth of personality disorder diagnosis from its articulation in the presence of mental state disorders, the longitudinal evidence of personality and its impact on later mental state disorder and its influence on outcome. All mental state disorder is too broad, so Depression and Substance Use Disorders are used as the exemplar internalising and externalising disorders of interest.
Aims
This thesis addresses three interrelated questions:
1. Is the nosology of personality disorder able to be defined in the presence of mental state disorder?
2. Does early personality impact on the development of later mental state and personality disorder?
3. Does personality affect the outcome of mental state disorder, and does the outcome of interest influence this?
Methods
Multiple methods were used to address these questions.
In section one, critical analysis of the literature was used to examine personality from a life course perspective in the presence of mental state disorder. On the basis of this analysis, an individual patient level re-analysis of data from four randomised controlled trials was undertaken in order to examine how differing nosological approaches (specifically a dichotomous, ordinal or continual diagnostic approach) could alter the impact of personality on the outcome of depression.
In section two the Christchurch Health Development Study, a longitudinal population based cohort, was interrogated to examine whether early personality impacts on later mental state disorder. The fact that this cohort is a birth cohort, with multiple potential moderators of impact available for analysis, allows for causal inferences to be made. Both regression modelling and generalised estimating equations were used in the analysis of later mental state disorder and substance use disorder respectively.
In section three, two systematic reviews and meta-analyses were undertaken to examine the impact of personality disorder on the outcome of depression and alcohol use disorder. Following this a critical appraisal of the standard psychopathology outcome measures is presented from a service user perspective, in the context of personality disorder. On the basis of this, regression modelling of the mental state and personality disorders associated with functional outcomes in a secondary care setting was undertaken to ask whether, using a functional outcome, personality is an important clinical indicator.
Results
A critical review of the literature indicates personality is a predictably changing set of interrelated domains, whose changes are beginning to be plotted over the life course. Despite this predictable change, in a combined analysis of 578 patients little difference in correlation was found between dichotomous, ordinal and continuous outcome measures of personality in depressed patients. At six weeks personality measures were of little value but statistically impacted on outcome at six months. This suggests personality disorder is increasingly important over time in the presence of depression, however what nosology is used is of less relevance.
Examination of the Christchurch Health and Development Study (CHDS) data set, including 987 30 year olds (80% of the original cohort) identified a correlation between neuroticism and extroversion at age 14 years and mental health and substance use disorders between the ages of 18 and 30 years. This association highlights poorer outcomes in the presence of neuroticism and the potential protective effects of extroversion in general for the development of mental state disorder. Examination of the dataset for the possible antecedents to substance use disorder identified both novelty seeking and neuroticism as associated with factors from a group of 24 possible early factors using general estimating equations.
The systematic reviews of the literature of personality disorder and depression and alcohol use disorder included 58 and 22 studies respectively. Personality disorder doubled the odds of a poor outcome for the treatment of depressive disorder although appeared not to impede gains in the treatment of alcohol use disorder. Notably the Alcohol Use Disorder (AUD) literature was not able to be adequately meta-analysed due to poor reporting and heterogeneity. Critical appraisal of these reviews, including 80 manuscripts, from a service user perspective suggests a functional outcome, as opposed to a psychopathological one, is of greater relevance. Bearing this in mind, regression modelling of diagnosis associated with functional outcome in secondary mental health care, across all disorders, indicated depression and personality disorder were of most importance.
Conclusions
Despite its changing nature, personality disorder can be assessed and formulated in patients with mental state disorders albeit how personality disorder is conceptualised from a taxonomic perspective may be less important. Neuroticism, an important facet of personality, impacts on the development of later mental state disorder and substance use disorder. Similarly, early personality is associated with the development of later substance use disorder. It is unsurprising therefore that personality disorder worsens the response to treatment in depressive disorder and may do likewise in alcohol use disorder. Taking a functional approach to outcome may be of greater value and here, both depression and personality are the primary diagnostic considerations in respect to functional outcome.