Many people are under the false impression that once a child is put down to bed everything is good and that rest follows. There are many facets to sleep and disordered sleep that is not very well explained by doctors, books and even well respected medical websites.
There are 3 stages of sleep:
Initiation - Ideally, when a child is sleepy, they lay down and fall asleep. Some need a “routine.” Any routing that takes longer than 10 minutes means that there is an issue.
Maintenance - Once asleep, deep in our brain, as switch flips to cause muscle paralysis so that we can drop down into deep REM sleep. Any movement, tossing and turning, “restless leg,” sleep walking, sleep talking, nightmares and night terrors means that the person in not in REM.
Arousal - When we wake up, if we have had multiple deep REM cycles, we wake up refreshed are are ready to start the day. Children should wake up happy and be ready bright and early. Be concerned if the child is cranky, sluggish or mean.
Children at different stages of development need a certain amount of sleep over a 24hr period.
During the 15-18 month, teething can disrupt sleep; true sleep issues can be teased out if teething pain is controlled-I like to use ibuprofen to help the pain.
Children under 4-5 years old should nap two times per day; Not including daycare schedule that child who resists naps or cuts out naps entirely at 2 years of age, is seriously sleep deprived. These kids can be cranky, clingy, hyper, meand or aggressive.