Tweaking the Body Clock to Ease SAD
Subtle Shifts May Help Patients Handle Seasonal Affective Disorder
April 24, 2006 -- Nudging the body's "clock," or circadian rhythm,
may help curb seasonal affective disorder (SAD), a new study
SAD is a depression that occurs each year at the same
time, usually starting in fall or winter and ending in spring or early summer.
The exact cause of SAD isn't known, but the amount of sunlight is an important
The new study included 68 SAD patients. The goal was to see if the
medication melatonin could adjust the patients' internal clocks to cope with
the later sunrise during winter.
The researchers included psychiatrist Alfred Lewy, MD, PhD, of Oregon Health
& Science University.
"Although more studies are needed, these data suggest that most SAD
patients might benefit from an appropriate low-dose formulation of melatonin
taken in the afternoon," they write.
The study appears in the online early edition of Proceedings of the
National Academy of Sciences.
Shifting the Body Clock
Lewy's team gave patients pills containing melatonin -- a hormone triggered
by darkness that helps govern the sleep/wake cycle -- or a similar pill without
melatonin (placebo). The body's pineal gland makes melatonin; melatonin
supplements are also widely available but aren't subject to the same U.S.
regulations as prescription drugs.
For three weeks during winter, the patients took a pill every two hours,
starting when they woke up and ending four hours or two hours before sleep, for
a total of seven or eight daily pills.
The patients were split into three groups. One group received melatonin in
the morning and a placebo the rest of the day; another group got placebo in the
morning and melatonin in the afternoon. The third group took placebo pills at
all times. No one knew which pills contained melatonin.
The pill schedule and doses were based on the theory that "most SAD
patients become depressed in the winter because of the later dawn," the
researchers write, calling melatonin "the chemical signal of
Lewy and colleagues checked the patients' depression severity before
treatment and every week during the study.
The researchers found that in most patients SAD was linked to delayed
sunrises. Those patients tended to respond best when they got melatonin in the
afternoon. Afternoon melatonin shifted their body clock to earlier in the
SAD appeared to be linked to winter's earlier sunsets in a smaller group of
patients. Those patients responded best when they took melatonin in the
The study shows that 17 patients received the "correct" treatment,
meaning they got melatonin at the time of day that suited their condition best.
In those patients, depression ratings decreased by 34%, compared with 13% to
15% for the other patients.
The study wasn't intended to test melatonin as a SAD treatment. Further
studies are needed for that, write Lewy and colleagues.
They add that their findings could also prompt new studies on nonseasonal
depression, as well as other sleep problems and psychiatric disorders that
might involve circadian rhythms.
The journal states that Lewy is a co-inventor on several melatonin-use
patents owned by Oregon Health & Science University, currently not licensed
to any company.