The purpose of this study is to evaluate the efficacy and safety of light therapy for the treatment of bipolar type II patients relapsing into a depressive phase during autumn or winter.

Bipolar type II depression is a very frequent condition for which we still have a significant lack of acute treatments. There is now consistent evidence that light-therapy treatment produced a significant decrease of depressive symptoms for seasonal and non-seasonal unipolar depression. But there are no long-term studies of light therapy for the treatment of non-seasonal unipolar depression. It is also important to note that many of these studies involved co-therapy with antidepressant drugs or sleep-deprivation, making the interpretation of the results even more difficult.

Therefore, we propose to study the efficacy and safety of light therapy for the treatment of bipolar type II patients relapsing into a depressive phase during the period of September to mid-March. This will be a double-blind randomized placebo-controlled study. Bipolar II out-patients will be recruited from our bipolar disorders program and from our 5 general psychiatry out-patient clinics. We will recruit bipolar type II patients facing a depressive phase and after they give their informed consent and we had verified they meet all inclusion and exclusion criteria, they will be randomized blindly to Bright-light (10 000 lux) vs Dim-light placebo (100 lux) therapies. Both, patient and investigator/rater will be blind to the type of light treatment assigned to the patient. The light therapy will take place during 30 minutes daily in the morning AFTER the usual awakening time of the patient in order to avoid even partial sleep deprivation which would confound the results if we were to observe a greater switch rate into mania or hypomania.

Reasons for study termination can be serious side-effects, development of suicidal ideations or hypomanic/manic symptoms, patient's own decision, or any other of the exclusion criteria being fulfilled during the course of the study.

Depressive and manic/hypomanic symptoms, quality of life, sleep quality and side-effects will be assessed at baseline and during the study. Biological parameters will also be measured along the study. We think that this study will allow us to determine the efficacy and safety of a 5 weeks bright light therapy for Bipolar type II depression and provide open label data as to the long term benefits of this treatment if prolonged over 5 weeks during the "dark" months of the year.

Inclusion Criteria:

• Bipolar type II disorder, depressive phase meeting DSM-IV criteria as per the SCID interview
• Hamilton Depression Rating Scale 21 items (HAMD-21) ≥ 17 and a Montgomery Asberg rating Scale (MADRS) ≥ 15 for at least 2 weeks and the episode has begun during the month of september or a later month
• Able to give their consent and willingness to participate to the study

Exclusion Criteria:

• Other psychiatric condition, organic brain disorder, unstable and/or untreated medical condition such as hypothyroidism, diabetes, cardiac condition, hypertension
• Deficit in vitamin B12 or folate
• Sub-syndromic hypomania symptoms as per a Young Mania Rating Scale (YMRS) score ≥ 4
• History of manic or hypomanic switch when exposed to bright light or during prolonged exposure to the sun during previous depressive phases
• Pregnancy or absence of a contraceptive treatment
• History of light-induced migraine or epilepsy
• Marked suicidal ideation
• Retinal blindness or severe cataract
• Glaucoma, retinal diseases of the eye
• Alcohol or drug abuse
• Known skin sensitivity to sunlight, especially in patients receiving photosensitizing drugs such as lithium or phenothiazines
• Past history of light therapy