Brighter Days Ahead: Light Therapy Effective for Bipolar Depression

John Watson


March 27, 2018

Building a Case for Light Therapy

In recent years, evidence has been mounting in support of bright light therapy (BLT) for the treatment of depression and other psychiatric illnesses. In results from a recently published randomized clinical trial,[1] researchers reported significant gains in patients with bipolar depression after just 6 weeks of BLT.

To find out more about these results and where BLT may be headed, Medscape spoke with the study's lead author, Dorothy K. Sit, MD, associate professor in the Department of Psychiatry and Behavioral Sciences at the Feinberg School of Medicine, Northwestern University in Chicago, Illinois.

Medscape: Please tell us a little about the history and background of BLT in psychiatric illness.

Sit: BLT is indicated by the American Psychiatric Association for the treatment of seasonal affective disorder.[2] Recent findings suggest that BLT alone or combined with fluoxetine was significantly more effective than placebo or fluoxetine alone for the treatment of nonseasonal depression.[3] Combined with a prior night of sleep deprivation, light therapy in the morning and possibly at midday can quickly reverse severe bipolar depression in supervised chronotherapeutic protocols.[4]

The response to morning light therapy is typically attributed to the circadian phase-resetting effects in seasonal and nonseasonal depression. However, the mechanism of action is unclear in bipolar disorder. Even so, patients with bipolar disorder are susceptible to environmental cues that alter circadian rhythms and trigger relapse. Depressed bipolar patients have symptoms of excessive sleep, increased appetite, lethargy, and delayed sleep phase (preference for late-night bedtime and wake time at mid-morning or noon), which are predictors of a positive response to light therapy.

For this reason, we completed a pilot study in women with stable depression in the context of bipolar disorder.[5] Morning light therapy induced a significant antidepressant response in one of four patients and, unexpectedly, hypomania in the other three patients.

To develop a strategy to minimize this undesirable risk, we consulted with experts in light therapy and chronobiology. Some colleagues were unable to demonstrate any antidepressant effect of morning light therapy versus placebo in patients with bipolar depression.[6] Others reported antidepressant effects from midday or evening bright light therapy for seasonal depression[7,8,9,10] or rapid cycling illness in small groups of patients.[11]

Given the evidence, we adjusted the timing of light therapy to midday and enrolled five more patients; three experienced a significant antidepressant effect from midday bright light, and one patient experienced a partial response from midday light and eventually a full response with a transition to morning light.

Medscape: What motivated you to study light therapy in bipolar disorder in the first place? Were there existing data in this area?

Sit: In the United States, 2% of the population has bipolar disorder.[1] Despite advances in the development of drug treatment for mania, effective treatments for bipolar depression remain limited.

Antimanic (mood stabilizer) drugs improve depressive symptoms in only one third of patients. Antidepressants prescribed without a mood stabilizer can result in hypomania and rapid cycling. The drugs for bipolar depression also induce problematic side effects, such as weight gain, fatigue, feeling too sedated, and uncontrollable agitation.

Given the limited treatment options, we decided to investigate novel therapeutics for bipolar depression.

Randomized Controlled Trial Results

Medscape: Can you briefly touch on the methods behind your study?

Sit: Building on the promising findings, we conducted a 6-week clinical trial to investigate the efficacy of BLT at midday for bipolar depression.[1] Study participants had moderate depression and no hypomanic or manic symptoms. Patients were randomly assigned to receive either 7000-lux bright white light or 50-lux dim red placebo light.

The light therapy unit conformed to stringent standards (illumination of a broad visual field, lighting from above to avoid glare, and maximal ultraviolet filtration). Participants were provided with standardized instructions on the appropriate use of their unit (optimal placement on its desk stand 12 inches from the eyes and advice to face the unit without directly staring at it) and agreed not to search for information on the design of the light box.

Patients were advised to use the light box daily at home or work, beginning with 15-minute sessions between 12:00 PM and 2:30 PM. Every week, the light therapy session was increased by 15 minutes until patients reached a dose of 60 minutes per daily session or until they experienced a significant clinical effect and regained normal functioning (remission).

We incorporated several important design elements to ensure that any observed differences in response were related to differences in the therapeutic effect of the active compared with the placebo light (and not from unbalanced expectations or other nonspecific effects).

Medscape: What were the results of the study?

Sit: After 6 weeks of bright light therapy, 68.2% of patients experienced remission from an episode of bipolar depression; patients had none or only low levels of depression and significantly better functioning. With dim red light, only 22.2% remitted and patients still had moderate depression levels plus persistent impairment in functioning.

The side effects were minimal, and no one experienced hypomania, mania, or a mixed episode.

Future Directions

Medscape: How effective do you believe light therapy is in bipolar depression compared with other established treatment—in particular, lithium?

Sit: It's an interesting question, but we don't have data to comment on this yet.

Medscape: What would you like to see follow-up research in this area address?

Sit: Compared with morning bright light, implementing bright light at midday induced robust antidepressant effects and possibly subtle effects on the circadian system, which might have mitigated the risk for hypomania or mixed symptoms. But whether the circadian effects of midday light therapy are detectable in bipolar depressed patients and correspond with an antidepressant response requires further investigation.

The large clinical effect of bright white light and the separation from placebo effect was clearly evident after 4-6 weeks of treatment. By judicious titration of the light dose, we postponed exposure to the maximum light dose. Even so, the dose-titration protocol still produced a cumulative therapeutic effect within the same time frame as same-dose protocols for patients with antepartum depression[12] and nonseasonal depression.[3]

Taken together, evidence from the study confirms the efficacy of adjunctive BLT for bipolar depression. This novel finding offers a real clinical advance and contributes an additional treatment option for bipolar depression. The use of a dose-titration protocol, implementing BLT at midday, and the requirement for concurrent antimanic (mood stabilizer) medication probably mitigated the risks for emergent mania or hypomania.

Given its efficacy, ease of use, and tolerability, midday light therapy appears ideally suited for depressed patients with bipolar disorder. In clinical outpatient care, we suggest this conservative approach for indicated patients with bipolar depression.

The unanswered questions that still demand further investigation include what are effective clinical strategies to prevent relapse; applications in special populations, such as pregnant women, children/adolescents, or elderly patients who may prefer nondrug somatic therapeutics; the biological mechanisms underlying the therapeutic effect of midday light therapy; and the development of individualized protocols based on biological markers to identify optimal responders.


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