According to the results of a historical study published in Psychiatry Research, the risk for switch from bipolar depression to mania after light therapy is similar to the spontaneous risk for switching expected during placebo treatment for bipolar disorder. These findings challenge existing concerns about the association of light therapy and switching to mania and may be useful for clinicians in developing treatment strategies for patients with bipolar disorder.
Researchers performed a historical review of 41 published reports describing the effects of antidepressant light therapy administered to patients with bipolar disorder. Samples were stratified per method used to identify treatment-emergent switches to mania: clinical mental state examination, rating scales, or not reported.
Of the 799 patients described across reports, 7 (0.9%) switched to mania and 11 (1.4%) switched to hypomania. The method of symptom assessment influenced the detection of treatment-emergent switches significantly (P =.005). Using rating scales resulted in a higher rate of detected switches than using clinical mental state examination alone (P =.031). Among studies using rating scales, 3.0% of patients switched to mania and 4.0% switched to hypomania. These figures are very similar to the 4.2% risk of switching to mania observed after placebo treatment for bipolar disorder. Among studies using clinical mental state examination, rates of switching to mania or hypomania were even lower (0.8% and 1.4%, respectively). Studies that did not report an assessment method also did not report switches to mania, although it was unclear to researchers whether this indicated a lack of switching or whether switching was simply not assessed.
Researchers noted that their conclusions were limited by the heterogeneity of light therapy treatment approaches and disparate symptom assessment methods. However, this large scale review of existing literature may be useful in determining the relative safety of light therapy for patients with bipolar disorder.
“Overall, these observations do not justify specific safety concerns for the risk of manic switches when using this treatment option in patients with bipolar depression,” the researchers concluded.
Benedetti F. Rate of switch from bipolar depression into mania after morning light therapy: A historical review. Psychiatry Res. 2018;261:351-356.