Physicians must then
consider the possible causes, which include: concurrent
medical conditions or their treatment; the use of
substances such as caffeine, nicotine, or alcohol; psychiatric
disorders, such as mood or anxiety disorders;
acute or chronic stress, such as that resulting from
bereavement; disordered circadian rhythms (occasioned
by jet lag, shift work, or advanced- or delayedsleep-phase
syndrome); sleep-disordered breathing
(heralded by snoring or obesity); nocturnal myoclonus,
sometimes associated with restlessness of the
legs at the beginning of sleep; events such as panic attacks
or recurrent nightmares during sleep; behavioral
conditioning, including excessive worrying about
not sleeping; and behavior that is destructive to sleep,
including an irregular schedule or the habit of lying
in bed ruminating.