LED LightLight-Emitting Diode (LED) Light for Seasonal Affective Disorder (SAD) Treatment

Recurrent fall/winter major depression (known as Seasonal Affective Disorder (SAD)) is a prevalent and disruptive disorder whose pathophysiological basis is unknown, but several hypotheses attribute a causal role to the circadian timing system. Bright white light exposure via the retina has been shown to reverse the symptoms of SAD. Recent physiological studies demonstrated the existence of retinal ganglion cells capable of transducing light input to the retinohypothalamic tract, the primary circadian afferent in humans. This retinohypothalamic system appears to be maximally sensitive to light in the 446-477nm (violet/blue) range.

Using light-emitting diode (LED) technology, light of narrow bandwidths now can be delivered from a safe, relatively inexpensive device. We propose to contrast in SAD patients the efficacy and tolerability of 468 nm LED light from a portable 11cm x 6cm commercially-available device (GoLITEÔ) to a broader 400-700 nm wavelength LED-generated light housed in an identical device. The broad wavelength (white) light from our LED device is similar to that from cool-white fluorescent 10,000 lux devices currently the standard for treatment of SAD (see e.g., Lam \& Levitt, 1999).

Twenty-four depressed SAD outpatients will be randomized to a 3-week trial of light therapy using either the narrow 468 nm LED source or the broader 400-700 nm LED source, each housed in a GoLITEÔ device. Subjects will be given devices and written instruction for administering daily treatments at home, 45min every (q) a.m. The devices will be described to subjects in terms of wavelength but not specifically described as "blue" or "white." Weekly depression ratings and assessments of adverse effects will be obtained by a trained rater blind to the treatment condition. Depressive symptoms will be rated weekly by the same trained clinician.

The following hypotheses will be evaluated:

• H1-- Depressed SAD patients will demonstrate greater antidepressant therapeutic benefit from the narrow-wavelength (blue) source than from the broad-wavelength (white) source.
• H2-- Depressed SAD patients will manifest fewer adverse effects during treatment with the narrow-wavelength (blue) source than with the broad-wavelength (white) source.