Early, Final Effects of SAD Tx Unrelated
By John Gever, Senior Editor, MedPage Today
Published: May 05, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner
· Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
· Early responses to light therapy for seasonal affective disorder (SAD) do not necessarily predict how patients will ultimately do on the treatment.
· Note that the lack of correlation between early and final outcomes occurred despite substantial declines in average symptom scores from baseline both after the first session and at the end of the six-week course of treatment.
PHILADELPHIA -- Early responses to light therapy for seasonal affective disorder (SAD) do not necessarily predict how patients will ultimately do on the treatment, a researcher said here.
In a placebo-controlled study of 79 patients with SAD, the correlation coefficient for outcomes after 1 hour compared with outcomes after 6 weeks was close to zero, said Monika Acharya, MD, of Baltimore University in Baltimore.
The lack of correlation came despite substantial declines in average symptom scores from baseline both after the first session and at the end of the 6-week course of treatment, she reported at the American Psychiatric Association's annual meeting.
For many medical conditions, early responses are predictive of medium- to long-term outcomes. In the case of light therapy for SAD, biological changes are detectable immediately, Acharya explained, which would suggest that the initial response could be used to identify patients who would benefit from continued therapy versus those who should be switched to alternative treatments.
She noted that previous studies had found that nearly half of SAD patients do not respond to light therapy.
The current study included 79 patients, about two-thirds female, with a mean age of 44. They qualified for a SAD diagnosis on the basis of structured clinical interviews and were not taking psychotropic medications.
Patients were randomized to an initial 2-hour session of bright white light or red light, the latter serving as placebo. Subsequently, all patients then received 6 weeks of daily, 1-hour treatment with white light in the morning.
After the first week, patients talked by phone with clinic staff each week about their responses, including side effects. The duration and timing of treatment could then be adjusted, Acharya said.
Depression symptoms were evaluated primarily with the SIGH-SAD instrument, a SAD-specific form of the Hamilton Depression Rating Scale. All patients had scores higher than 20 at baseline with a mean of 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. Some 63% of patients were responders and 31% had symptoms resolved by week 4; after another 2 weeks of treatment, 82.1% had responded and 58% were in remission.
But responses after 1 hour and after 6 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% reduction in SIGH-SAD scores after the first session -- seen in nine participants -- significantly associated with remission at 4 or 6 weeks.
On the other hand, she and her colleagues found that body mass index did correlate significantly with response, such that patients with a higher BMI had greater responses to the light therapy.
Acharya told MedPage Today that the flexible dosing allowed in the study was a significant limitation. She did not have data on whether there was a relation between outcomes after the first session or at later evaluations and patients' dosing patterns during the trial.
Primary source: American Psychiatric Association
Acharya M, et al "Early response to bright light and outcome at six weeks" APA 2012; Abstract NR1-51.