According to sleep expert Dr.Robert Schacher,many people have difficult sleepinh,but thay do not know why.Most people know it is important not to drink coffee or tea before thay go to bad-both beverages have caffeine.Caffeine keeps people awake.Hwever,not everyboby knows that some medicines,such as cold tablets,also have caffine in tham.stress can cause insomnia,too.Busy people with stressful jobs may not be able to sleep at night.