Bright light therapy for bipolar depression

Prescribing bright light therapy

Light box selection criteria. When selecting a light box or related BLT treatment apparatus, the Center for Environmental Therapeutics recommends consideration of the following factors³⁵:

• clinical efficacy
• ocular and dermatologic safety
• visual comfort.

The intensity of the light hitting the cornea depends on the distance from the light. In our experience, when the patient is facing the box it should provide 10,000 lux when he or she is 1 foot away at approximately a 45° angle (1 lux = 1 lumen per square meter). The light box selected should emit full spectrum white light with UV filter. The newest filters use LED, which is less expensive and more durable. Typically, we’ve found that it is most convenient for patients to use the light box in the morning before 9 am, but around noon is preferred for patients with BD. If using a light box is not feasible, we suggest the use of dawn light by the bedside before waking in the morning. Again, it is preferable to get some sunshine outdoors while taking a walk as long as geographical location and weather conditions permit.

Selecting a dose. The dose received is determined by the intensity emitted from the light source, distance from the light box, and duration of exposure.³⁶ Begin with midday light therapy between 12 noon and 2 pm at a daily dose of 15 minutes, and increase by 15 minutes every 2 weeks until the patient has achieved a euthymic mood.³⁴ Patients need not stare directly into the light source as long as the light is able to meet the eye at an angle of 30° to 60°.³⁵ The upper limit of midday light is 45 to 60 minutes, beyond which patients are more likely to have difficulty with adherence. Because morning BLT also may be effective, consider a change to morning light at a starting dose of 15 minutes for patients who respond partially or minimally to 45 to 60 mins of midday light, then increase it every week by an additional 7 to 15 mins.³⁵ For patients who respond to BLT, it is reasonable to continue light therapy for 12 months after remission to prevent relapses, similar to the recommendations for antidepressant therapy.³⁴

Monitor for adverse effects. Generally, BLT is well tolerated.³⁷ Adverse effects are rare; the most common ones include headache, eyestrain, nausea, and agitation.³⁸ One study found no adverse ocular effects from light therapy after 5 years of treatment.³⁹ Adverse effects tend to remit spontaneously or after dose reduction.³⁵ Evening administration of BLT may increase the incidence of sleep disturbances.⁴⁰ Like other biologic treatments for bipolar depression, BLT can precipitate manic/hypomanic and mixed states in susceptible patients, although the light dose can be titrated against emergent symptoms of hypomania.⁴¹

Bottom Line

Evidence suggests that bright light therapy is an effective, well tolerated, and affordable adjunct treatment for bipolar depression. Exposure to 5,000 to 7,000 lux around noon for 15 to 60 minutes will enhance the remission rate.

Related Resource

Mostert M, Dubovsky S. When bipolar treatment fails: what’s your next step? Current Psychiatry. 2008;7(1):39-46.

Drug Brand Name
Lithium • Eskalith, Lithobid