October 29, 2001
Dopamine, Parkinson's Personality Link Debunked
By Merritt McKinney
NEW YORK (Reuters Health) - Results of a new study challenge the idea
that a personality type often
present in people with Parkinson's disease (news - web sites) is
directly related to brain levels of the neurotransmitter dopamine.
The research does not dispute the existence of a ''parkinsonian
personality,'' but the findings suggest
that low levels of dopamine may not be the cause.
It has long been suggested that many people with Parkinson's fit a
certain personality
type--compulsive, hard-working, introverted, morally rigid, serious and
quiet.
Some studies have shown that people with the disease receive low scores
on tests of
``novelty-seeking.'' Normally, the brain rewards pleasure--such as a new
experience--with the release
of the brain chemical dopamine. Some scientists have speculated that low
dopamine levels--one of the
characteristics of Parkinson's--may explain why people with the disease
are less likely to seek out new
things.
But in a study reported in the November 6th issue of the journal
Proceedings of the National Academy
of Sciences (news - web sites), Dr. Valtteri Kaasinen and colleagues at
the University of Turku in
Finland did not find a connection between dopamine levels and low
``novelty-seeking'' in people with
Parkinson's.
In the study, the researchers gave personality tests to 61 people with
Parkinson's who were not taking
medication for the disease and a ``control'' group of 45 healthy people.
The investigators also
measured dopamine levels in 47 unmedicated Parkinson's patients.
Parkinson's patients scored somewhat lower than controls on the
novelty-seeking test, the report
indicates. But there was no significant connection between
novelty-seeking and dopamine levels in
several parts of the brain.
Parkinson's patients had significantly higher scores on measures of
``harm-avoidance,'' which relates to
anxiety and depression. Surprisingly, Kaasinen and colleagues found that
the higher scores were linked
to higher levels of dopamine in one part of the brain.
The more patients felt pessimistic, fearful of uncertainty and shy, the
higher were their levels of
dopamine in an area called the right caudate nucleus.
This connection ``is difficult to explain with our current knowledge,''
according to the researchers.
Kaasinen's team suggests that it is possible that a ``unique disturbance
of circuitry'' in the brains of
people with Parkinson's might explain the paradox. It is possible that
the link between that tendency to
avoid harm and high levels of dopamine in the right caudate might occur
in depressed or anxious
people with other chronic diseases, the researchers note.
SOURCE: Proceedings of the National Academy of Sciences 2001;98:13272-
Copyright © 2001 Reuters Limited.
Copyright © 2001 Yahoo! Inc.
--
Judith Richards, London, Ontario, Canada
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