Punctual, self-controlled, industrious, even-tempered. These
are often traits that people aspire to in some way or another. They are also
traits that seem to be overabundant in people with Parkinson’s disease.
At the heart of the disorder is a problem with
neurotransmitters. Dopamine is the key player in the smooth movements controlled
by the deep brain structures that are affected in PD, and loss of dopamine (by
PD or something that mimics PD) results in the slow, stiff movements that are
so characteristic of the disorder. PD is more than just a movement disorder
though, and the same neurotransmitter is also responsible for decision making,
thought process and reward seeking.
We understand that the underlying process that causes PD
actually starts up to a decade before the person notices slowing, stiffness and
tremor. We also know that there are some things that are well known to be
harbingers of PD – for instance anxiety/depression, constipation, loss of sense
of smell, particular sleep disorders.
There are also some things that seem to be ‘protective’ against the
disease, for example smoking, high caffeine consumption and alcohol
consumption.
Could all of these be linked by subtle changes to a person’s
personality? For example, someone who is the ‘life and soul’ of the party (i.e.
highly extrovert, with high novelty seeking behaviour) may be more likely to
smoke and drink, and be less anxious and depressed.
When it comes to marrying these observations with Parkinson’s
disease, I am left wondering, which is the chicken and which is the egg, and
ultimately, can we ever work out which comes first?
This paper doesn’t answer the question, but it is a good
place to start to understand where the current understanding comes from, from
clinical, behavioural and biological perspectives.
As ever, please join the discussion below.
RNR
Personality in Parkinson's disease: Clinical, behavioural
and cognitive correlates.
Gabriella Santangelo et al
J Neurol Sci, 2017 vol 374 pp17-25
Affective disorders and personality changes have long been
considered pre-motor aspects of Parkinson's disease (PD). Many authors have
used the term "premorbid personality" to define distinctive features
of PD patients' personality characterized by reduced exploration of new
environmental stimuli or potential reward sources ("novelty seeking")
and avoidance behaviour ("harm avoidance") present before motor
features. The functional correlates underlying the personality changes
described in PD, implicate dysfunction of meso-cortico-limbic and striatal
circuits. As disease progresses, the imbalance of neurotransmitter systems
secondary to degenerative processes, along with dopamine replacement therapy,
can produce a reversal of behaviours and an increase in reward seeking, laying
the foundations for the emergence of the impulse control disorders. Personality
disorders can be interpreted, therefore, as the result of individual
susceptibility arising from intrinsic degenerative processes and individual
personality features, in combination with extrinsic factors such as lifestyle,
PD motor dysfunction and drug treatment. For a better understanding of
personality disorders observed in PD and their relationship with the prodromal
stage of the disease, prospective clinical studies are needed that correlate
different personality profiles with other disease progression markers. Here, we
review previous studies investigating the clinical, cognitive and behavioural
correlates of personality traits in PD patients.
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