People who experience prolonged depressive symptoms starting
in young adulthood may have worse thinking and memory skills
in middle age, according to a new study. The study involved
3,117 people with an average age of 30 at the start of the
study. Participants were evaluated for depressive symptoms
every five years for 20 years. At each visit, they completed
a questionnaire asking if they experienced changes in
appetite or sleep, had problems with concentration or
experienced feelings of worthlessness, sadness or
loneliness. Higher scores represented more symptoms.
Researchers divided participants into four groups based on
the progression of their symptoms over time: persistently
low symptoms, medium decreasing, persistently medium or high
increasing symptoms. There was a higher proportion of Black
participants, 52%, in the persistently medium group, as well
as the high increasing depressive symptoms group with 70%.
Five years later, when participants had an average age of
55, they were given three tests to examine thinking and
memory skills. For example, on a test that measures
processing speed and memory, participants were given a key
showing numbers and corresponding symbols. Then had to draw
those symbols on a separate list of random numbers as
quickly as possible. The score range was zero to 133 with
lower scores representing worse cognition. Those in the low
symptom group had an average score of 73, in the medium
decreasing group, an average score of 71, persistently
medium, a score of 66 and high increasing, an average score
of 57. After adjusting for factors such as age, physical
activity and total cholesterol, among Black participants,
those in the high symptom group had an average score that
was 0.64 standard deviations below the average score for the
low symptom group. Among white participants, those in the
high symptom group had an average score that was 0.40
standard deviations below the average score for the low
symptom group. Researchers created a standardized score for
each of the three cognitive tests. After adjusting for
factors such as education, blood pressure and total
cholesterol, researchers found among Black participants,
those in the three groups with high and medium symptoms had
worse verbal memory, processing speed and executive function
scores when compared to those in the low group. Researchers
found among white participants, those in the high symptom
group had worse verbal memory and processing speed scores
when compared to those in the low symptom group. A
limitation of the study was that symptoms were self-reported
and no clinical diagnosis of depression was available.
|