*Initial Response to Light Therapy Doesn’t Predict Outcome*
Published on Psych Central
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[image: Initial Response to Light Therapy Doesnt Predict Outcome]Patients’
initial responses to light therapy for seasonal affective disorder (SAD)
may not indicate how much it ultimately helps them, according to a
researcher from Baltimore University in Baltimore, Md.
Monika Acharya, M.D., speaking at the American Psychiatric Association’s
annual meeting in Philadelphia, said that in a placebo-controlled study of
79 patients with SAD, the correlation coefficient for outcomes after one
hour compared with outcomes after six weeks was close to zero.
Yet patients’ symptoms declined noticeably from baseline, both after the
first session and at the end of the treatment course, she noted.
Early responses to treatment for many medical conditions can predict mid-
to long-term outcomes, Acharya said. Biological changes from using light
therapy for SAD are detectable immediately, suggesting that patients’
initial response could predict those who would benefit from continued
Previous studies have found that nearly half of SAD patients do not respond
to light therapy.
Acharya’s study included 79 patients, about two-thirds female, with a mean
age of 44. They were diagnosed with SAD through structured clinical
interviews; none of them was taking psychotropic medications. They were
randomly assigned to an initial two-hour session of bright white light or
red light (the red light being the placebo).
Following the initial session, all patients then used white light one hour
every morning for six weeks.
Patients followed up weekly by phone with clinic staff and reported their
responses. Side effects and the duration and timing of treatment could then
be addressed, Acharya said.
Depression symptoms were evaluated primarily with a SAD-specific form of
the Hamilton Depression Rating Scale, the SIGH-SAD form. All patients had
baseline scores over 20 (mean 32.3).
The first treatment led to small reductions in SIGH-SAD scores in both the
white- and red-light groups: 1.6 points with white light (P=0.03) and 0.8
points with red light (P=0.20).
After 4 weeks, mean scores had dropped to 12.7, and by week six they had
declined further to an average of 8.3.
Sixty-three percent of patients were responders and 31 percent had symptoms
resolved by week four. After another two weeks of treatment, 82.1 percent
had responded and 58 percent were in remission, according to Acharya.
But responses after one hour and after six weeks were not correlated at
all, Acharya reported, irrespective of whether they were assigned to red or
white light at the first session. Nor was a 20 percent reduction in
SIGH-SAD scores after the first session — seen in nine participants —
significantly associated with remission at four or six weeks.
On the other hand, she and her colleagues found that body mass index did
correlate significantly with response: Patients with a higher BMI had
greater responses to the light therapy.
The study’s flexible dosing was a significant limitation, Acharya said. No
data was available on whether there was a relation between outcomes after
the first session or at later evaluations and patients’ dosing patterns
during the trial.
Source: American Psychiatric Association »>