Is your child easygoing, or does every little setback or disappointment lead to a tantrum? If he still takes naps, does he settle down without much fuss, or fight like crazy and then crash out during playdates or on short car trips? Later, is bedtime a battle?

Some seemingly minor decisions you make throughout the day may be setting you up for these power struggles. For instance, if you let your child stay up past his usual bedtime as a treat, give him a late lunch, or let him watch TV just before he turns in, you may unknowingly be upsetting his body clock.

This internal timer is the control center for the body's sleep-wake cycle. And it needs to be set  -- with things like good sleep habits, a proper diet, and well-timed exercise. Throw it off, and your child will be wide-awake when he ought to be sleeping, drowsy when he needs to be alert, and grumpy more often than he should be.

By identifying the things that disrupt your child's body clock, you can often avoid  -- or at least plan around  -- them.

Does your child go to bed and/or wake up 30 to 60 minutes later on weekends than on weekdays?

It's tempting to let your child turn in late on Friday or Saturday night, figuring you'll let her sleep in the next morning. Why not bend the rules when she doesn't have daycare or school?

But if she's used to getting up at a certain time, she'll probably still awaken then  -- short of sleep and irritable. By naptime (if she still naps) she'll be overtired and unable to settle down until later in the afternoon. And because her nap will be late, it's likely she'll be up watching the 10 o'clock news with you.

If, by some chance, your child does sleep late, it's likely to be poor-quality rest. She'll awaken feeling groggy because she's not in sync with her body rhythm.

The symptoms of your child's off-kilter body clock may not be obvious. In fact, they may seem more like misbehavior. She'll insist she can't sleep, beg for another glass of water or bedtime story before turning in, and come get you every time she wakes up in the wee hours. The next day she'll be even more sleep-deprived, and her internal timekeeper will continue to struggle.

None of this means that you can never spend a late evening at a friend's or let your child stay up later on a weekend night. Just think about the pros and cons before you do it, knowing there's a good chance that it may make the following day tougher for you both.

Adapted from Sleepless in America: Is Your Child Misbehaving or Missing Sleep? by Mary Sheedy Kurcinka, copyright © 2006 by Mary Sheedy Kurcinka. Published by arrangement with HarperCollins Publishers.

---