Recent medical advances (American Journal of Psychiatry, Rosenthal et al, 142:2, 163-70) have demonstrated that light can be used to treat certain types of depression, specifically, Seasonal Affective Disorder (SAD). SAD is a condition in which an individual feels depressed and lethargic with a tendency to overeat, oversleep and crave carbohydrates. In its more severe forms, the affected person is totally withdrawn and unable to successfully function in society. This disorder is most commonly observed during the winter months, when skies are cloudy and overcast, with long periods of little or no natural sunlight exposure. Many persons experiencing "winter blues", or "cabin fever" are probably experiencing some lesser degree of SAD or light hunger. Most persons affected note marked relief from their symptoms of depression after exposure to sunlight, for instance during and following winter vacations to sunny climates.
Current scientific research in the physiology behind this phenomenon points to the effect of light on the retinohypothalamic tract in either suppressing or stimulating production of certain neurotransmitters, i.e. melatonin and serotonin respectively, known to be responsible for neuroendocrine changes of circadian rhythm in animal models and of mood and affect in human models. While current light therapy utilizing stationary indoor apparatus is being applied to patients with bipolar type II SAD in psychiatric clinical settings, it is felt by the inventor that the normal individual experiencing the common "winter blues" would receive benefit from a portable light source administering experimentally determined minimal doses of light to suppress melatonin, thus producing an anti-depressant effect. Detailed information on the neurophysiology of daily exposure to light on both animal and human models is presented in Science, Lewy et al, 1980; 210:1267.
There are devices in the prior art providing light exposure for the treatment of SAD, but these devices are large, bulky, stationary metal enclosures having banks of fluorescent daylight tubes commonly referred to as "light boxes". The proposed invention is a full spectrum portable light source of 5000.degree. K. sufficient power to deliver a premeasured dose of light of at least 500 lux over a period of time from a position indirect to the user's eyes. In effect with this invention, the user is exposed only to the type and amount of light he would experience if he were in a bright, sunny environment.
The present invention is an improvement over existing fixed devices in that it provides a portable light source worn on the user's head, not only for therapeutic outpatient use by those individuals suffering from SAD, but for a person living in those latitudes and geographic locations that experience prolonged, low-sunlight winter conditions. It is anticipated that some percentage of the population experiences SAD in such mild to moderate severity that their condition goes undiagnosed because it did not warrant psychiatric consultation. It is this group that will benefit from the proposed invention in the form of elevated mood, better overall performance, less susceptibility to stress and consequent depression, and higher energized levels for all activities of daily living. Insofar as this effect will be achieved by natural physiologic process using full spectrum light as neuroendoctrine stimulant, it is emphasized that the user would experience no ill effect than he normally would upon being exposed to natural sunlight of the same duration and intensity.