Some individuals with sleep onset insomnia experience difficulty falling
asleep at a “normal time” but no difficulty maintaining sleep once it is initiated.
Individuals with this type of insomnia may have a delayed or later timed
circadian rhythm. Bright light therapy timed in the morning after arising can
advance or time circadian rhythms earlier and thus would be indicated for
sleep onset or initial insomnia. Morning bright light therapy is also indicated
for the related problem of delayed sleep phase disorder.
Individuals experiencing early morning awakening insomnia have no difficulty
initiating sleep but their predominant difficulty is waking before intended
and not being able to resume sleep. These individuals may have an advanced
or early timed circadian rhythm. Bright light therapy in the evening before
sleep would be indicated for this type of insomnia as well as for the more