Alzheimer's, Dementia & Mental Health
Why is late-life depression harder to treat?
Seniors' Abnormal Reaction to Emotional Stimuli
This finding offers important clue in search for
more effective therapies
May
4, 2010 - Scientists have found an important clue in the
quest to understand why people who suffer from depression in later life
are harder to treat and keep well in the long term. A study led by
Toronto's Baycrest has found that older people with depression don't
respond normally to emotional stimuli, such as when they see happy, sad
or neutral faces.
The study appears online this week in the
American Journal of Geriatric Psychiatry and is likely the first
published data to focus specifically on emotional processing in
un-medicated older adults with late-life depression.
"In our study we found significant differences
between older depressed subjects and older healthy subjects in how they
emotionally respond to and perceive facial expressions," said principal
investigator Dr. Linda Mah, a clinician-scientist in the Mood Clinic at
Baycrest.
Emotion dysregulation is already well established
in mid-life depression and some studies have shown it to be predictive
of a relapse of mood symptoms. But the majority of late-life depression
studies have concentrated on the link with cognitive decline, suggesting
that the more impaired the cognitive functions the greater the chances
of a poor prognosis in depression.
"Our data suggest that we need to also focus on
emotion to better understand the neurobiology of late-life depression,
so we can treat it more effectively and help people feel better longer,"
said Dr. Mah.
In the study, 11 un-medicated outpatients with
major depressive disorder, and 11 healthy comparison subjects,
participated in two tasks that involved looking at photographs of faces
with happy, sad, fearful or neutral expressions.
The age range of participants was 60 to 87.
In the first task, participants were asked to make
judgments regarding a physical feature of faces, rather than judging the
emotional expression. In the second task, participants were asked to
label the emotional expressions on faces.
The study found that healthy controls were 16%
slower in making judgments about physical features of the faces with
positive or negative emotional expressions (happy, sad, fearful)
relative to neutral faces an indication that they were distracted or
affected by the emotional expressions on faces.
The depressed participants showed no differences in
response time to rating physical aspects of faces with emotional
expressions or neutral faces. This suggests they were less sensitive to
the effects of positive or negative emotional expressions.
In the second task, depressed participants had
greater than 60% more difficulty with correctly labeling neutral faces,
compared to healthy subjects. Depressed participants misread neutral
expressions as happy, sad or fearful.
Dr. Mah noted that an impaired ability to read
other people's emotional expressions can have social consequences and
affect the quality of social interactions with others.
She also pointed out that these abnormalities in
emotional processing seen in older depressed adults are distinct from
those already reported in younger depressed adults who tend to perceive
and process emotional stimuli more negatively overall when compared to
healthy subjects.
About the study
The Baycrest study included small sample sizes, so
the results should be considered preliminary. Efforts are ongoing to
recruit older patients who are currently not on antidepressant
medications, and to use functional neuroimaging to pinpoint the brain
changes underlying the abnormalities in emotional processing that appear
to be associated with late-life depression.
In addition to her psychiatric practice at
Baycrest's Mood Clinic, Dr. Mah is a clinician scientist at Baycrest's
Rotman Research Institute as well as the Kunin-Lunenfeld Applied
Research Unit. She is also an assistant professor of Psychiatry, in the
Division of Geriatric Psychiatry, at the University of Toronto.
Dr. Bruce Pollock, the Sandra A. Rotman Chair in
Neuropsychiatry at Baycrest and the University of Toronto, assisted in
this research. Dr. Pollock is vice-president of Research at CAMH, Chair
of the Division of Geriatric Psychiatry at U of T, and an
internationally-renowned expert on the effects of drugs on mood and
behavioural disturbances in dementia.
The Baycrest study was funded by the Geoffrey H.
Wood Foundation, the University of Toronto's Dean Fund, the National
Institute of Health, and the Sandra A. Rotman Chair in Neuropsychiatry.
