LIGHT TREATMENT FOR SLEEP DISORDERS - CONSENSUS REPORT .3. ALERTING AND ACTIVATING EFFECTS

In addition to the well-established phase-shifting properties of timed exposure to bright light, some investigators have reported an acute a lerting, or activating, effect of bright light exposure. To the extent that bright light interventions for sleep disturbance may cause subje ctive and/or central nervous system activation, such a property may ad versely affect the efficacy of treatment. Data obtained from patient s amples and from healthy subjects generally support the notion that exp osure to bright light may be associated with enhanced subjective alert ness, and there is limited evidence of objective changes (EEG, skin co nductance levels) that are consistent with true physiological arousal. Such activation appears to be quite transient, and there is Little ev idence to suggest that bright light-induced activation interferes with subsequent sleep onset. Some depressed patients, however, have experi enced insomnia and hypomanic activation following bright-light exposur e.