Winter Depression Linked
with Melatonin Cycle
NEW YORK (Reuters Health)
- People with seasonal affective disorder (SAD) instinctively
shift their melatonin levels with the seasons, paralleling the
hibernation patterns of mammals, according to US researchers.
This does not appear to be true for those who don't react to
shorter days and longer nights with deepening depression, their
study findings indicate.
``In patients who had SAD, the duration of melatonin secretion
became longer in winter and shorter in summer, just as it occurs
in other mammals,'' lead author Dr. Thomas A. Wehr, a research
psychiatrist at the National Institute of Mental Health in Bethesda,
Maryland, told Reuters Health. ``That could be controlling this
panoply of changes that occurs in people when they get depressed
in the winter.''
Seasonal affective disorder, or ``winter depression,'' is a psychiatric
disorder that strikes during winter months, when daylight hours
are naturally shortened. The disorder in humans seems to mimic
the behavior exhibited by hibernating animals, such as increased
sleep and decreased activity.
Melatonin, a hormone produced by the pineal gland in response
to the darkness of nighttime, promotes sleep and helps regulate
the body clock. Hibernation in mammals is triggered when the brain
responds to the body's increase in melatonin production.
Prior research suggests that people with seasonal affective disorder
are unable to use artificial light to readjust their body clock,
but remain susceptible to the seasonal rhythms of shorter daylight
hours during wintertime.
The researchers compared melatonin levels in 55 SAD patients
with levels in a ``control group'' of 55 healthy volunteers. All
of the study participants were placed in a dimly lit room for
24 hours and the amount of melatonin in their blood was measured
every half hour, once during the winter and again during the summertime.
As expected, Wehr's team found the healthy individuals were immune
to shifts in the natural daylight, with their melatonin levels
remaining stable throughout the seasons. However, those with winter
depression had a moderate decrease in the length of time they
produced melatonin during the summertime.
The duration of active melatonin secretion was about 9 hours
in the control group, whether in winter or summer. In the SAD
group, active melatonin secretion was 9 hours in winter and 8.4
hours in summer, according to the report in the December issue
of the Archives of General Psychiatry.
``We're seeing a remnant of our own evolutionary heritage,''
Wehr said. ``The fact that the symptoms resemble changes that
animals experience speaks to a root of this problem in evolutionary
These findings also suggest that medications that curtail the
longer duration of melatonin production may be an effective treatment
for these patients. ``Anything you can do to manipulate melatonin
signals might be useful as a treatment for seasonal depression,''
Wehr said. ``If you could trim off the last hour or two melatonin
is produced, you would convert a winter signal to a summer.''
SOURCE: Archives of General Psychiatry 2001;58:1108-1114.
Reference Source 89