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(HealthNewsDigest.com) – TORONTO, Aug. 2, 2011 – Heavy smokers may experience sadness after quitting because early withdrawal leads to an increase in the mood-related brain protein monoamine oxidase A (MAO-A), a new study by the Centre for Addiction and Mental Health (CAMH) has shown. This finding, which was published in the Archives of General Psychiatry, may also explain why heavy smokers are at high risk for clinical depression.
Using an advanced brain imaging method, a team led by Senior Scientist
Dr. Jeffrey Meyer discovered that MAO-A levels in the brain regions
that control mood rose by 25 per cent eight hours after withdrawal from
heavy cigarette smoking. These levels were much higher than in a
comparison group of non-smoking study participants. All 48 participants
filled out questionnaires, and smokers with high brain MAO-A levels
during withdrawal also reported greater feelings of sadness.
“Understanding sadness during cigarette withdrawal is important because
this sad mood makes it hard for people to quit, especially in the first
few days. Also, heavy cigarette smoking is strongly associated with
clinical depression,” said Dr. Meyer, who holds a Canada Research Chair
in the Neurochemistry of Major Depression. “This is the first time
MAO-A, a brain protein known to be elevated in clinical depression has
been studied during cigarette withdrawal.”
MAO-A “eats up” chemicals in the brain, such as serotonin, that help
maintain a normal mood. When MAO-A levels are higher as in early
cigarette withdrawal, it means that this removal process is overly
active, making people feel sad. For this study, MAO-A was detected
using a brain imaging technique called positron emission tomography
(PET). CAMH has the only PET scanner in the world dedicated solely to
mental health and addiction research.
A specific substance in cigarette smoke, called harman, may be
responsible for these changes, the researchers note. During active
smoking, harman attaches to MAO-A. During early withdrawal in heavy
smokers who had 25 or more cigarettes a day, MAO-A levels rose rapidly
to a level beyond that seen in the healthy comparison group.
“This study opens new ways to prevent sad mood during cigarette
withdrawal to make it easier to quit smoking. For example, it may be
possible to improve the existing cigarette filters that partially
screen out harman, or regulate the amount of tryptophan contained in
cigarettes, since tryptophan becomes harman when it burns,” said Dr.
Meyer, who is also head of the Neurochemical Imaging Program in Mood
Disorders at CAMH’s Research Imaging Centre, and professor of
psychiatry at the University of Toronto. “We also identified MAO-A as a
target to shut down during the early critical stage of withdrawal with
a short course of medication, but this requires further study.”
“This finding may explain why heavy smokers are at high risk for
clinical depression,” says Dr. Anthony Phillips, Scientific Director of
the Canadian Institutes of Health Research’s (CIHR’s) Institute of
Neurosciences, Mental Health and Addiction, which funded this study.
The study was also supported by the Ontario Mental Health Foundation,
the U.S.-based Brain and Behavior Fund (formerly NARSAD), and the
Canada Foundation for Innovation.
The Centre for Addiction and Mental Health (CAMH) is Canada’s largest
mental health and addiction teaching hospital, as well as one of the
world’s leading research centres in the area of addiction and mental
health. CAMH combines clinical care, research, education, policy
development, prevention and health promotion to transform the lives of
people affected by mental health and addiction issues.
CAMH is fully affiliated with the University of Toronto, and is a Pan
American Health Organization/World Health Organization Collaborating
Centre.
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