Abstract Personality is central to our understanding of what it means to be an individual. As neurodegenerative diseases become increasingly prevalent in our aging population, this dissertation asks how two common conditions, Parkinson’s Disease and Alzheimer’s Disease, affect personality, what this means for carers, and why there hasn’t been more research into this area. The dissertation begins by introducing the reader to some key areas of contemporary personality research before moving on to collate some of the key studies in this area and critically evaluate the strength of the evidence pointing towards personality transformation. The second section then considers the implications of these findings with regards to personality theories and research, the needs of carers and future research into this area. The dissertation concludes that evidence to support personality transformation in Parkinson’s Disease is currently insufficient, due to contradictory findings, and the absence of large, prospective trials. Similarly, whilst a consistent pattern of personality change is emerging in Alzheimer’s Disease, methodological issues such as the reliance on retrospective assessments highlight the need for longitudinal cohort studies in this field. Key reasons for the lack of rigorous investigation may include the widespread belief that personality is by definition static, the likelihood that changes in neurological illness are confounded by current symptoms and the multiplicity of scales employed in the literature, leading to the perception that personality research is ineffective and unimportant. However, it is argued that research in this area could have numerous practical applications, from aiding early diagnosis to testing new treatments and supporting carers through effective distribution of NHS resources. Therefore, further research is essential to improve diagnosis, treatment and support for those affected by neurodegenerative diseases.
274 Words
Personality Transformation in the Injured Brain
Personality Transformation In the Injured Brain
By Felicity Jones St John’s College Supervised by Dr Luke Clark
Personality Transformation in the Injured Brain
Introduction In recent years, much progress has been made in considering personality transformation in traumatic brain injury, and a variety of other conditions, however this has largely been based around a consideration of focal damage and there has been little consideration of studies into diseases which cause more diffuse damage. Classic cases of personality transformation such as those of Phineas Gage and Elliot/EVR (Damasio, 1998) have shown situations in which personality can be significantly altered by brain damage, and these have prompted a range of questions: does personality transformation only occur in such cases of penetrating head injury and tumour resection, or are there a range of conditions which can cause change? To what degree do individuals in this situation have the capacity to make choices - are they victims of their brain injury? What are the psychosocial
consequences
of
personality
change?
This review aims to collate the key studies and reviews of personality change across two neuropsychiatric conditions which pose major public health issues, and are becoming leading causes of DALYS (Disability-Adjusted Life-Year) due to their increasing prevalence as the population ages. In the UK alone, there are 750,000 people affected with
Alzheimer's
and
over
120,000
people
affected
with
Parkinson's
Disease.
(Alzheimer’s Society, 2010, Parkinson’s UK, 2010). Both conditions cause diffuse damage, but are reasonably well-understood in terms of their underlying pathology. This dissertation will then critically consider the implications of this research with regards to models of personality, treatment options, and psychosocial consequences. Such a review must be broad in order to be useful, but necessitates a brief consideration of a number of underlying key concepts in psychology, before moving on to consider specific studies in more detail.
Personality Transformation in the Injured Brain
Personality is traditionally seen as a static rather than dynamic entity; for example it has been defined as “the relatively enduring patterns of thoughts, feelings, and behaviours that distinguish individuals from one another” (Roberts and Mroczek, 2008). With the advent of the western philosophical-political individualistic stance, a fascination with personality as a key distinguishing factor between individuals has flourished in a society where “the person” is seen to be bounded by the skin and is at the heart of our understanding of what makes us human. I will outline relevant theories of personality and personality change before moving on to consider literature around transformation in Parkinson’s and Alzheimer’s and its implications.
Relevant Theories of Personality This section will outline two key models of personality structure which will be referred to in the literature discussed. Cloninger’s model of personality has been strongly drawn upon by psychologists exploring the effect of Parkinson’s disease upon personality, largely because Parkinson’s is believed to largely result from the depletion of dopamine neurones in the substantia nigra, and this model offers direct hypotheses about dopamine. The model proposes that there are 3 core dimensions of personality which lie at 45 degrees to Eysenck’s PEN (Psychoticism, Extraversion and Neuroticism) Model, and are related to the strength of response in three neurotransmitter systems. The dimensions are: Harm Avoidance- related to serotonin, Novelty Seeking- related to dopamine, and Reward Dependence- related to noradrenaline. This had led to a number of questionnaires including the Tridimensional Personality Questionnaire (TPQ), the Temperament and Character Inventory (TCI) and the Karolinska Scales of Personality (KSP). Whilst derived from Cloninger’s model of personality the latter two scales are based on 4 dimensions, with the additional dimension of persistence (Stewarta, Ebmeierb and Deary, 2004).
The second model relevant to this dissertation is the “Big Five” Model which has been
Personality Transformation in the Injured Brain
widely used to assess personality structure in Alzheimer’s. In the 1990s, researchers considering the structure of personality in healthy individuals began to reach an astonishing consensus surrounding a five factor taxonomy. Costa and McCrae (1999) proudly lauded their model ‘the Christmas tree on which findings of stability, heritability, consensual validation, cross-cultural variance and predictive utility are hung like ornaments’. This now extremely popular model proposes the following factors (although some psychologists disagree with the names): O = Openness (to experience), Conscientiousness, Extraversion, Agreeableness and Neuroticism, and is measured predominantly with
Costa and McCrae’s NEO-PI-
R
questionnaire
of 240 items
(Figure 1).
Fig 1: The ‘Big 5’ Model of Personality Costa and McCrae propose that personality is composed of these five continuouslydistributed core dimensions. The diagram uses adjectives to describe the characteristics of an individual who lie to the extreme ends of each spectrum (green and pink), situations in which the personality trait may affect behaviour (blue), and a possible brain mechanism by which the personality trait may operate (beige). (Taken From http://www.gp-training.net/training/leadership/five_facets.htm ) Both these theories are widely used within the field of personality studies, and whilst the Big Five model has gained far more accolade, the lack of associated neurobiological
Personality Transformation in the Injured Brain
hypotheses has meant that other models, such as Cloninger’s, are still widely employed.
The Non-Pathological Mutability of Personality The controversy about scientific evidence for personality transformation has raged unabated for over a century. Classic theories of psychology viewed adult personality as a static entity, with William James (1890) famously proposing that personality was set "in plaster" by early adulthood, and Freud (1923) stating that personality was determined even earlier, at completion of the Oedipal stage of development, at an age of just 5. By the 1950s there was increasing literature proposing personality change in adulthood, with psychologists such as Erikson (1950) positing that adults (like children) pass through stages of life, during which they mature and change.
With the emergence of the Five Factor Model of personality in the 1990’s, theorists returned to the “set like plaster” hypothesis.
Costa and McCrae’s review in 1984
concluded from their longitudinal studies that ‘personality traits are stable in adulthood: There are no age-related shifts in mean levels, and individuals maintain very similar rank ordering on traits after intervals of up to 30 years’. Although their assertion that rank ordering remains stable has been supported by a number of reviews (e.g. Roberts and Mroczek, 2008), the claim that mean levels remain static has been disputed by a wealth of data which strongly support the idea that personality changes significantly during adulthood. Dramatic individual studies have played a key role in prompting this change of view. For example, an internet survey of 132,515 adults aged 21–60 showed significant changes in three of the five factors; Conscientiousness and Agreeableness increased throughout early and middle adulthood, and neuroticism decreased with age, but only in women (Srivastava et al., 2003). Thus this very large study strongly supports the idea that personality changes in population cohorts across time.
Studies such as these have led to several recent reviews into personality change in healthy individuals. These have often considered all three possible forms of change;
Personality Transformation in the Injured Brain
rank-order consistency, mean level change, and individual level change, and claim that both mean-level and individual changes are highly significant, as shown in figure 2 (E.g. Roberts and Mroczek, 2008; Edmonds et al., 2005). They even point to the likelihood of cross-cultural universals in the “patterns� of mean-level change (although more nonwestern replication is required to determine this as the generalisability of much published research is problematic).
Fig 2: Personality Change in Adulthood. Change in personality traits over time for six train domains. These graphs were created by adding average amounts of standardized mean-level change from separate decades of the life course together, under the assumption that personality-trait change may be cumulative. Extraversion is broken into its constituent subdomains of social vitality and social dominance.
Personality Transformation in the Injured Brain
(Taken From Roberts B, and Mroczek D, Personality trait stability and change. Current Directions in Psychological Science 2008; 17: 31-35.) Thus, although debate continues about the extent of personality change in populations and the individual, a large and growing body of literature concludes that change is both a normality and reality for most individuals and for the population as it ages. Studies have also begun to highlight the myriad circumstances in which transformation can occur as an abnormal process, as the result of pathology. This review will now move on to consider personality change in two such examples of pathology; Parkinson’s and Alzheimer’s diseases.
Research into Parkinson’s and Personality Transformation
According to Parkinson’s UK, one person in every 500 has Parkinson's Disease (PD), thus this disease has a huge burden on the NHS, and affects many lives both directly and indirectly (Parkinson’s UK, 2010). Therefore any findings about changes in personality (and its subsequent effects on behaviour and the experience of carers) as a result of the condition have significant implications. In recent years there has been increasing interest in the ideas of a premorbid Parkinsonian personality, and a possible personality transformation, based on Cloninger’s model of personality and characterised by a decrease in novelty-seeking (NS) and increase in harm-avoidance (HA). However, few studies have been conducted to aid in distinguishing between these two possibilities, since most work in the field has been cross-sectional. This section aims to consider the background of the concept of personality transformation in Parkinson’s and review some key studies, before calling for more, rigorous work to determine whether personality transformation does indeed occur in Parkinson’s.
Personality Transformation in the Injured Brain
Clinicians have long claimed that there are specific personality traits associated with PD, and emerging literature supports this belief. James Parkinson originally described the disease as a purely neurological and motor condition with “the senses and intellects being uninjured" (Parkinson, 1817). More recently we have been able to understand PD as a condition which reduces dopamine in the substantia nigra due to neuronal degeneration. Alongside this scientific understanding there is increasing awareness of associated mental changes in PD, such as depression and intellectual impairment.
As imaging tools became available, researchers became interested in examining the personality of PD patients. Menza et al. (1993) used PET tomography to show that uptake of [18F]dopa in the left caudate significantly correlated with novelty-seeking, and reviewed evidence which suggested that this was due to a dopamine deficit, specifically resulting from damage to the mesolimbic dopaminergic system. This correlation sparked a great deal of excitement and has been widely cited, despite being based on only 9 patients, and led to interest in whether this was a cross-cultural phenomenon (Fujii et al., 2000). They asked 67 Japanese PD patients to complete the TPQ and demonstrated significantly lower NS and significantly higher HA scores, compared with matched controls. However, these studies, along with the vast majority of work in the area, are cross-sectional, and thus do not enable conclusions about personality transformation to be drawn.
There is a dramatic absence of prospective research into this area, however, a recent study by Arabia et al. (2010) followed 6,882 subjects over 4 years after they completed the Minnesota Multiphasic Personality Inventory (MMPI), a scale commonly used by clinicians. 227 subjects developed Parkinsonism, but sensation-seeking was not correlated to incidence. This may indicate that changes in novelty-seeking are as a result of the condition rather than causal. Nonetheless, it does not rule out the possibility of mediating factors such as age.
Personality Transformation in the Injured Brain
This section will consider a number of cross-sectional studies (Figure 3) to see whether
Study
Jacobs H et al. (2001)
N
122 PD X < 52 years
Methods
1) 2)
122 controls
1) 2)
Kaasinen V et al. (2001)
61 nevermedicat ed PD. 45 controls.
26 nevermedicat ed PD Bódi N et al. (2009)
1) 2)
22 recentlymedicat ed PD 24 controls 1) 2)
Kaasinen V et al.
28 PD patients
TPQ Testing of formal intelligen ce and depressio n. TCI and KSP In 47 PD: 6-[F18]fluoro -L-dopa (F-18dopa) positron emission tomograp hy (PET) with MRI coregistrati on. Hungaria n TCI In nevermedicate d PD: 6[F18]fluoro -L-dopa (F-18dopa) positron emission tomograp hy (PET) TCI [11C]FLB 457 positron emission tomograp hy
Results
1) 2) 3) 4)
1) 2) 3) 4)
5)
Novelty seeking (NS) did not differ Harm-avoidance (HA) Depression "Persistence" (Part of RewardDependence)
NS NS did not correlate with F-18dopa uptake (r = -0.12 to 0.11, P > 0.15). HA HA positively correlated with F18-dopa uptake in the right caudate nucleus (r = 0.53, P = 0.04) (Paradoxical). HA correlated with depression
Conclusions 1)
2)
1) 2)
1) 1) 2) 3) 4)
1)
NS (P = 0.04, uncorrected) HA (P = 0.03, corrected). NS did not correlate with F-18dopa uptake. HA negatively correlated with 18 F-dopa uptake in R(r = 0.53, P = 0.04, corrected), but not L (r = 0.43, P = 0.88, corrected) caudate nucleus.
NS negatively correlated with dopamine D2 availability bilaterally in the insular cortex (P = 0.0001, corrected). R: r = 0.74 L: r = 0.66
2)
3)
1)
Doesn’t support PD Personality type with regards to NS Depression explains Harm avoidance
Supports PD Personality type But this PD Personality type not dopaminedependent.
Supports PD Personality type But this PD Personality type not dopaminedependent. High HA associated with high 18F-dopa uptake in R caudate nucleus.
Suggests a link between NS and insular D2 receptors.
they can be considered to support this key study. It will then consider a theory proposed by Tomer and Aharon-Peretz (2004) which attempts to pull the findings together.
Fig 3: Key studies measuring personality transformation in PD Patients
Personality Transformation in the Injured Brain
Studies used questionnaires derived from Cloninger’s Model of Personality (commonly the TCI). Findings are contradictory; however three studies report an increase in harm avoidance. Abbreviations: R = right, L = left, D2 – Dopamine Type-II
Overview of Parkinson’s Disease Studies These studies were selected based on the significance they carry in the field, despite a number of limitations. One of the most significant issues with other research into PD is that most studies use patients who have received and are continuing to receive medications, and who have other conditions concurrently. This makes it difficult to distinguish between treatment and disease effects, and to identify the impact of PD. All three of these studies attempt to deal with these issues by studying unmedicated PD patients, and in two cases young and recently-diagnosed patients, and use matched controls to consider correlations with a number of other variables, thereby increasing their validity. The study by Jacobs et al. is particularly good at ruling out confounding factors since it has very well-matched controls.
This use of unmedicated patients may increase the validity of the results by allowing researchers to distinguish between treatment and disease effects. For example, it led Kaasinen et al. (2001) to suggest that the low novelty-seeking behaviour identified in earlier studies could be partially due to the effects of long-term dopaminergic medication, since they didn’t find as large an effect as studies such as Menza et al. (1993). The downside of using these specific patient groups is the small sample size of the studies. This seriously limits the power of studies in a field already afflicted with problems relating to the reliability and validity of the scales employed to provide statistical outcomes.
Personality Transformation in the Injured Brain
Nonetheless, a number of conclusions can be drawn from these studies. All 3 studies considered novelty-seeking, and whilst Jacobs et al. (2001) does not find a significant reduction in NS in PD patients, the authors propose this may be due to recruiting patients by letter, without a reminder, as those with low NS may have hesitated to respond. In contrast, both the studies by BĂłdi et al. (2009) and Kaasinen et al. (2001) identify a significant deficit of novelty-seeking in those with PD, whilst not supporting a link between NS and dopaminergic function. Kaasinen et al. (2001) suggest that the NS comparison may have become statistically significant with a larger subject sample as the result was just below 0.05 and not corrected for multiple comparison.
Despite these contradictory findings, Suhara et al. (2001) demonstrated a robust correlation between NS and dopamine D2 receptor binding in the right insular cortex using [(11)C]FLB 457 PET in 24 healthy patients, and this convincing correlation was replicated in 28 PD patients by Kaasinen et al. in 2004 (P = 0.001), particularly on the right side. Such a correlation has also been ruled out in the striatum by similar studies (E.g. Breier et al., 1998). These studies support the possibility of a cross-cultural phenomenon, and offer a mechanism by which PD may affect NS. A serious weakness in this finding, however, is that the cause of the negative correlation is not yet clear; possibilities could include genetically-regulated low concentrations or afďŹ nity of D2 receptors, or changes in D2 receptor expression due to ďŹ&#x201A;uctuations in endogenous dopamine levels. This is certainly an area ripe for further exploration. The dimension of harm-avoidance is also common to all the studies referred to herein, and was uniformly found to be raised. This may reflect a particular feedback circuitry associated with the depression also prevalent in PD (Kaasinen et al., 2001). A metareview by Cummings et al. found that the level of depression in PD stands at 40%; far more than one would expected on a reactive basis compared to other physical illnesses with equal disability scores (P < 0.001) (Menza et al., 1994). Furthermore, in this study HA correlated strongly with depression (P < 0.001) and explained 31% of the variance in depression scores; a finding supported by Jacobs et al, which also found that depression
Personality Transformation in the Injured Brain
rates were independent of disease severity or duration. Thus it seems likely that harmavoidance is raised in PD, however, there are a number of alternative possible explanations for the link; for example HA may increase due to depression, or dopamine may act as a mediating factor.
The contradictory findings in this field have been assessed by Tomer and Aharon-Peretz who hypothesised that reduced NS reflects deficits in the mesolimbic branch of ascending dopamine transmission in the left hemisphere, whereas increased harm avoidance might be associated with neuronal loss in the right striatum. They tested this suggestion in 2004 by dividing 40 patients with Parkinson’s disease into two groups according to initial asymmetry in dopamine deficit. The asymmetry of the dopamine deficit was determined by a neurological examination and the patients’ reports regarding the side and presentation of motor symptoms (left hemisphere, n = 22; right hemisphere, n = 18). All subjects and 17 controls then completed the TPQ. The results strongly supported their hypothesis as only patients with greater dopamine loss in the left hemisphere showed reduced NS (Scheffe; p = 0.02) and only those whose symptoms began on their left side reported increased levels of HA (Scheffe; p = 0.042) compared to controls.
Despite the small sample size reducing its generalisability, numerous potential confounding factors such as disease severity and cognitive functioning showed no correlation with either NS or HA, and it may explain the previously controversial findings. For example, Bódi et al. used too small a sample size to test differences between patients with right- and left-sided motor symptoms, but 20 of the patients displayed right-sided symptoms (left-hemisphere dopamine deficiency) alongside reduced noveltyseeking. Furthermore, a correlation between HA and
18
F-dopa uptake was seen in the
right (r = 0.53, P = 0.04, corrected), but not in the left (r = 0.43, P = 0.88, corrected) caudate nucleus. Future research is necessary to support or disprove this theory; for
Personality Transformation in the Injured Brain
example
replicating
Tomer
and
Aharon-Peretz’s
findings
(2004)
would
increase
reliability.
The authors’ conclusions and the studies discussed above must be examined rigorously in relation to the methodologies used, and the strength of the supporting evidence. This essay now highlights a number of key limitations in this research.
As previously mentioned, none of these studies apart from Arabia et al, 2010 can clearly indicate a transformation in personality, due to their cross-sectional, rather than prospective nature. However, the study by Bódi et al. (2009) studied patients who, on average, had been diagnosed for just 3 months, suggesting that at the least, these are early signs of Parkinson's disease, and thus might be useful for diagnosis. In order to determine whether this might be useful there is a real need to invest greater attention into the way patient personalities are structured, mapped and assessed if they are to be used as markers which either act as a risk or result of PD.
Perhaps the most serious problem facing the field is the multiplicity of scales and techniques employed, which make it difficult to compare findings or draw conclusions, as highlighted by this use of the MMPI. Whilst the dopaminergic nature of Cloninger’s model clearly lends itself to Parkinson’s, it is surprising that there hasn’t been work on personality transformation in Parkinson’s disease and the Big Five using the NEO-PI-R questionnaire since it is arguably better respected. This is an important issue to consider for future research.
In reviewing the literature, no conclusive data was found to support the likelihood of personality transformation in Parkinson’s disease, as findings in this area have been contradictory. Considering our understanding of the changes in brain structure
Personality Transformation in the Injured Brain
associated with Parkinson’s, further research might fare well by correlating these changes in personality characteristics to changes in brain structure or activity.
Research into Alzheimer’s and Personality Transformation
Alzheimer’s disease (the most common form of dementia) is a progressive disease which affects daily living through memory loss and cognitive changes. Personality changes are a key area doctors may ask about when diagnosing the condition (National Institute of Aging, 2010). So far much of the literature in this area (Figure 4) strongly supports the hypothesis that personality changes in AD occur with a clear and consistent pattern.
The nine studies in Figure 4 measured both premorbid and current personality scores, so were able to evaluate change. They showed strikingly similar changes in all 5 dimensions of the NEO-PIR; the typical results in standard deviation (SD) units were a decrease of 3 SD in Conscientiousness, an increase of 2 SDs in Neuroticism and a similar decrease in Extraversion, and reductions in Openness and Agreeableness (around 1 SD). These are the opposite of the changes reported in healthy individuals, thus clearly pathological.
Nonetheless, these studies (reviewed by Wahlin and Byrne, 2010*) suffer from some serious weaknesses, and thus this pattern must be questioned. Firstly,
a third of the
studies included non-Alzheimer’s patients: studies included vascular dementia, mixed dementia (Kolanowski et al., 1997), atypical dementia, ‘memory disorders’ (Siegler et al., 1991) or ‘severe dementia’ (Williams et al., 1995), which may have confounded the results. Additionally, the effect of prescribed drugs and severity of the Alzheimer’s could well be important – these were not clear in all studies and could also have acted as
Personality Transformation in the Injured Brain
confounding factors. Lastly, it is difficult to compare the studies as they used different methodologies (e.g. the time period over which premorbid personality was considered) and participant characteristics (e.g. age or severity of dementia).
* Published after I had completed my literature review
Personality Transformation in the Injured Brain
Study
N
Siegler et al
35 patients
(2001)
Only 13 AD
Informant 28 spouses, 7 children and siblings
Scale
NEO PI 181
38 AD
24 spouses, 12 children, 1 sister-in law, 1 LT companion
NEO PI
22 AD
14 spouses, 7 children, 1 housemate
NEO PI
29 AD
23 spouses, 5 children, 1 other relative
NEO PI
Siegler et al (1994)
26 AD
24 spouses, two primary caregivers
NEO PI 181
Williams et al (1995)
36 Severe Dementi a
26 spouses, 7 children, 1 sister, 2 landladies
NEO PI 60
Welleford et al (1995)
36 DAT
28 spouses, 6 children, 1 sibling, 1 nephew
NEO PI
Kolanowsk i et al (1997)
19 AD, MID and unspecifi ed
‘Usually’ sons and daughters
50 AD
46 spouses, 3 children or sibling, 1 close friend
Chatterjee et al (1992)
Strauss et al (1993) Strauss et al (1994)
Dawson et al (2000)
Change in Personality Scores in SD Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓ Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness↓↓. Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓. Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓. Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓. Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓. Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓.
Typical Results? Typical Results
Only a 2 SD decrease in Conscientiou sness Typical Results
Typical Results
Typical Results
Typical Results
Typical Results
NEO PI -R
Neuroticism ↑, Extraversion ↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓.
Only 1 SD increase in Neuroticism and 1 SD decrease in Extraversion
NEO PI 181
Neuroticism ↑↑, Extraversion ↓↓, Openness ↓, Agreeableness ↓, Conscientiousness ↓↓↓.
Typical Results
Fig 4: Key studies measuring personality transformation in AD Patients All studies used questionnaires derived from Costa and McRae’s 5-Factor Model of Personality (commonly the NEO-PI) and showed predictable and consistent shifts in personality (7 out of 9 studies showing identical changes). Abbreviations: Each arrow represents approx. 1 standard deviation (SD), DAT =Dementia Alzheimer’s Type, MID= Multiple-Infarct Dementia, LT = Long-Term
Personality Transformation in the Injured Brain
Lastly, the fact all 9 studies had small sample sizes (X ≤ 50) leads us to question the generalisability and validity of the review’s findings. Bearing these limitations in mind, however, the pattern of personality change was surprisingly consistent.
It is also important to acknowledge that studies in AD patients face additional problems because they may not be able to reliably report on their personality, due to a lack of self-awareness and memory; or a lack of insight which Stone et al. (2004) term ‘emotional agnosia’. Therefore most of the studies included in the review, and in the literature more generally, utilise retrospective assessments. Unfortunately, these assessments may be generated by faulty memories of
an individual’s previous
characteristics (Chatterjee et al., 1992) as a relative’s perception may be biased by the current symptoms of the patient, whilst other studies suggest that patients do actually have quite good insight (Rankin et al., 2005). Ideally, therefore, a prospective longitudinal study would be employed; interviewing both healthy individuals and their close relatives, and following the cohort to measure what proportion develop Alzheimer’s. However, since this is expensive and time-consuming, these studies are far and few between, and the concerns with regards to retrospective assessments must lead us to question the validity of the reported emerging pattern of personality transformation.
Additionally, some researchers such as Clément and Teissier (2010) have proposed that certain premorbid personality traits predict the risk of dementia, as well as any changes in personality by the disease. They used both the TCI and NEO-PI, and found that the risk of dementia is increased by high levels of harm-avoidance on the TCI, or low levels of extraversion, openness, agreeableness and conscientiousness, and a high level of neuroticism on the NEO-PI –the same pattern shown in the 9 studies discussed.
These expositions fail to consider another possible explanation; that the personality transformation is a result of AD which precedes cognitive decline, and thus diagnosis
Personality Transformation in the Injured Brain
with Alzheimerâ&#x20AC;&#x2122;s, a hypothesis supported by two of the few prospective studies in the literature (Smith-Gamble et al., 2002; Balsis, Carpenter, and Storandt, 2005). If this was the case then personality change could be an important marker for the early onset of the disease. Currently diagnosis is complex, and based only on tests of cognitive decline, but early diagnosis is hugely beneficial as it aids management of the condition. For example, it may lead to the
use of pharmaceuticals and behavioural interventions,
which may help slow cognitive decline. Changes in Neuroticism and Conscientiousness have been shown to discriminate healthy controls from those with early stage AD better than these existing tests (Duchek et al., 2007; Wilson et al., 2008). Therefore if personality transformation is seen to be as uniformly significant as these 9 key studies suggest, it could prove a key clinical marker. In order to verify this pattern, additional prospective, longitudinal studies are needed, which interview both the individual and their relatives where possible, and use autopsy to verify diagnosis.
Lastly it is important to consider the clinical importance of these changes in personality. For example, decreased Conscientiousness alongside a lack of memory may contribute to the hygiene issues common in AD patients, whereas increased Neuroticism may lead to more frequent and profound psychological distress. Decreased Extraversion may promote apathy and further impair already problematic interpersonal relations. These personality changes therefore have huge implications for the behaviour of the patient, and thus their carers, and it is the impact of this which the review will now move on to consider.
Personality Transformation in the Injured Brain
Coping With Personality Transformation: Caregivers and their Burdens The majority of care for patients with both Alzheimer’s and Parkinson's disease is provided by informal caregivers. This care is emotionally valuable for patients, and financially benefits the NHS by reducing the community care required, and preventing early nursing home placement. However, this caregiving places a huge burden on the caregiver and their family and can have many negative effects. In a survey of 123 caregivers to PD patients over 40% of caregivers felt their health had suffered, over 65% reported their social life had suffered and nearly 50% (Schrag et al., 2006). As well as clearly having a huge effect on their own life, the caregiver burden scores correlated with the patients' depression and quality of life score. This suggests that supporting caregivers adequately is not only important for their benefit, but also for the health of their patients.
There is a particularly high burden placed on caregivers of AD patients who exhibit disturbing behaviours and functional limitations, which led to frequent depressive symptomatology in a study by Clyburn et al. (2000). Perhaps more surprisingly, this study showed that caregivers in this position received less help from family and friends, highlighting the importance of formal care provision for these patients; a finding with high generalisability due to the unusually large number of patients and caregivers followed (n=613).
Personality changes have long been seen to constitute a major part of the caregiver’s burden, not least because they contribute to disturbing behaviours. Teri (1997) highlights the ways in which a patient’s behavioural dysfunction (such as withdrawal, apathy and depression) can hugely affect caregivers’ burden - patterns of behaviour which could arise from personality changes such as a decrease in Extraversion and increase in Neuroticism. Furthermore patient’s personality changes are perceived as
Personality Transformation in the Injured Brain
more stressful, more threatening, less manageable and of greater centrality in comparison to physical changes by carers (Kausar and Powell, 1999.) Thus personality changes in neurodegenerative conditions contribute significantly towards caregiver burden, and are a key issue that should be considered with regards to distribution of NHS resources in order to support carers.
Further work has examined which particular dimensions of personality contribute most significantly towards caregiver burden. Personality transformation and significant relationships between perceived current patient personality, caregiver personality, and caregiver burden were shown in a study of 36 patients with Alzheimerâ&#x20AC;&#x2122;s by Welleford et al. (2005). They reported that current patient Conscientiousness and caregiver Neuroticism were the best predictors of both objective and subjective burden, and that these variables were found to contribute independently to caregivers' reported level of burden. Hooker et al. (1997) tried to explain individual differences in caregiversâ&#x20AC;&#x2122; abilities to cope with the stress their role entailed. Their study of 175 caregivers (88 AD; 87 PD) reported that personality had significant direct and indirect effects on mental health and significant indirect effects on physical health, and that patient Agreeableness and Conscientiousness were the most important dimensions in determining burden. They also found that caregiver personality is important; as caregivers who had higher scores on Neuroticism tended to experience lower social support, higher perceived stress, and worse psychological health, whereas those higher in Extraversion experienced better social support. Moreover, Alzheimer's disease spouse caregivers felt more depressed and more anxious than Parkinson's disease spouse caregivers, and had significantly worse mental health than PD caregivers. However, AD caregivers had better physical health than PD caregivers.
Thus several studies propose a need for formal care provision in cases of patients with highly disturbed behaviour or significant personality changes, particularly in the Agreeableness
and
Conscientiousness
dimensions.
Furthermore,
interventions
for
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caregivers could be well-targeted based on knowledge of the social support available, and the caregiver’s trait characteristics, with more support being advisable for caregivers high in Neuroticism and low in Extraversion. Whilst more replication of the results is necessary in order to produce an evidence-base with which to inform policy, these studies suggest that personality scales may prove a useful way of determining where to direct NHS resources in order to support patients and their caregivers. This could prove a cost-effective method of distributing resources in order to prevent caregivers developing costly mental and physical health problems.
Discussion of Findings and Implications Data from several studies have identified personality transformation in both Parkinson’s and Alzheimer’s diseases. In PD, Cloninger’s model of personality has been applied to point to a possible increase in novelty-seeking and decrease in harm-avoidance. In AD, Costa and McCrae’s model, tested largely by the NEO-PI, has revealed systematic shifts on all five scales; a decrease in all dimensions apart from neuroticism, which increases. Whilst neither of these reported trends is backed by the wealth of rigorous studies needed to propose policy, there is enough of a pattern emerging, particularly in the case of Alzheimer’s, to merit more studies in the field to determine the reliability of the results.
As the policy implications inherent to this field of research have been addressed, what follows is a discussion of the implications of these studies upon current models of personality structure and work which is attempting to link traits to different regions of the brain or different neurotransmitters. Lastly this section will focus on the potential of personality questionnaires to act as a diagnostic marker or a clinical indicator of whether a treatment is having an effect.
Personality Transformation in the Injured Brain
As referred to previously, Cloninger linked novelty-seeking to dopamine systems. As Parkinson’s is believed to largely result from the depletion of dopamine neurones in the substantia nigra, and NS has been shown in several studies to be affected in these patients, this appears to support this hypothesis. Further, there has been a correlation identified between NS and dopamine D2 receptor-binding in the insular cortex (particularly on the right-hand side) in both healthy controls and PD patients (Suhara et al., 2001; Kaasinen et al., 2004). This seems to suggest that NS is related to the dopamine systems affected in Parkinson’s, particularly the insular cortex. However, since the insula borders the striatum, possible spatial misalignment and the use of the raclopride D2 tracer (with which it is difficult to resolve any binding outside the striatum) make it difficult and unwise to attempt to localise NHS to specific areas of the brain.
With such a small sample size, caution must be applied, as these studies have little statistical power, and PET has not yet supported a link between dopaminergic function and the low novelty-seeking reported in Parkinson's disease. Thus there is no clear support for Cloninger’s model from this work as yet. Even if a strong correlation NS and dopamine D2 receptor binding in the right insular cortex were to be revealed, it would be important to determine the cause of the negative correlation in order to develop an effective treatment as there are a whole range of possible explanations for this phenomenon.
Thus, although these preliminary findings are interesting, there is a lot more work to be done before any conclusions can be drawn with regards to future treatments or support of Cloninger’s model. At first glance the decrease in HA shown by some studies in PD patients seems to dispute the one-to-one link he theorised; and although it is possible that serotonin might also be involved this is difficult to determine without further work.
Personality Transformation in the Injured Brain
Unfortunately, the widespread amyloid plaques and neurofibrillary tangles and similarly diffuse atrophy of the cerebral cortex characteristic of AD make it more difficult to connect specific brain areas and particular personality dimensions. Additionally, since the “Big 5” Model has no proposed neurobiological foundation, the studies considered cannot support or disprove the model. Nonetheless, the diffuse neuropathology could explain the widespread changes in personality experienced by those suffering from Alzheimer’s disease.
Next the role of this research in developing diagnostic or clinical markers must be considered. As previously mentioned, increases in Neuroticism and decreases in Conscientiousness on the NEO-PI been shown to discriminate healthy controls from those with early stage AD better than these existing tests (Duchek et al., 2007; Wilson et al., 2008). This shows the potential usefulness of personality scales as a predictive tool to help determine who will develop, or is developing a neurodegenerative condition. However more replication of these results in large prospective studies which use autopsy to determine diagnosis is necessary in order to determine whether this discrimination is robust enough to be used in this manner.
Additionally, personality scales could prove a useful way of testing new treatments, and treatments which affect personality change are likely to have significant benefits with relation to caregivers’ burden, as discussed previously. For example, a study by Punrandare et al (2002)
examined the effect of anticholinesterase treatment on
personality changes in AD by asking 58 carers to complete the Brooks and McKinlay Personality Inventory for each of three periods in the patients' lives: before the onset of AD, after the diagnosis of AD but before starting anticholinesterases, and when on anticholinesterases. This found significant personality changes upon onset of AD, but their results suggested that anticholinesterases may have a positive effect in preventing
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and reversing the change. This preliminary finding would need to be validated by further double blind prospective studies, but it echoes similar work in other conditions. For example, a placebo-controlled trial of depressive patients found that taking the SSRI paroxetine led to a significant decrease in neuroticism and increase in extraversion, even after controlling for the improvement in their symptoms of depression (Tang et al, 2009). Thus these studies are strong examples of the potential utility of an understanding of the interaction between personality and a disease, in order to assess potential treatments.
Adopting a more critical approach to what are considered to represent valid research practices, there are few reviews and little assimilation of data amongst researchers within this fieldâ&#x20AC;&#x201C; a notable exception being the recent review on Alzheimerâ&#x20AC;&#x2122;s (Wahlin and Byrne, 2010) which pulls together studies from the last twenty years. If these had been collated at an earlier date not only would there have been a more easily-determined consensus on what conclusions could be reached on the existing literature, but also a method to determine what further research needed to be done.
A consideration of studies into Parkinsonian personality suggests this is a particular problem in this field; the ongoing debate about the likelihood of a pre-morbid personality has led to numerous, non-prospective studies with small sample size using a whole variety of scales. These poor quality studies have duplicated one another, but never had enough power to lead to a conclusive result, and the mixture of techniques and scales employed have made it difficult to conduct a meta-analysis. Related to this controversy has been the neglect of the possibility of a personality transformation until fairly recently. Arguably a single, large, prospective study which measured personality before and after individuals had developed Parkinsonâ&#x20AC;&#x2122;s would have been a more useful and conclusive way of reporting on both hypotheses, but unfortunately no such study took place until recently (Arabia et al., 2010). Again this emphasises the need for several
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large studies which measure personality before, at the onset, and throughout the progression of a disease in order to draw more robust conclusions about personality transformation in neurodegenerative conditions.
Another significant challenge to be overcome is the perception of personality research as an invalid and unimportant field of study. Key reasons for this include widespread beliefs that personality is by definition static, the likelihood that changes in neurological illness are confounded by current symptoms and lack of insight etc (as mentioned in the section on AD) and the lack of consensus over scales in the literature. Despite a lot of evidence supporting Costa and McCraeâ&#x20AC;&#x2122;s five factor model some psychologists continue to use their preferred scale of choice, which can be baffling to the outer world and leads to a lack of respect of personality psychology from healthcare professionals. In order to improve the status of the field the usefulness of this research for health improvement, for example as a diagnostic marker for Alzheimerâ&#x20AC;&#x2122;s, needs to be made clear.
Personality scales which are currently employed in a healthcare setting have been designed for patients with particular illnesses; for example the Neuropsychology Behaviour and Affect Profile (Nelson et al., 1989) has been used in conditions including stroke, dementia and closed head injury patients. Neurologists have been reluctant to replace these with scales derived from the Big Five, as it has no neurobiological basis. However, collaboration with trait psychologists to design personality measures that are informed by illness aetiology but also describe of basic traits might lend authenticity to the field, and produce more reliable and valid scales for further research; there is a real need to invest in developing tools that acknowledge, and give a role to the qualitative, psychological aspects of the condition. These new scales might also encourage the longitudinal, prospective studies required to draw robust conclusions about the extent of personality transformation in neurodegenerative conditions.
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