Your preschooler is throwing more tantrums, whining more, having nightmares; he’s started sucking his thumb or wetting the bed again. And just when you thought he was over his separation anxiety, he clings to you and cries when you’re heading off to work. Something is stressing him out.

Yes, even little kids get stressed. Research shows that cortisol levels in toddlers and preschoolers often increase as they attempt to play with lots of other kids in day care. This can even top separation-from-Mommy stress. Home issues like money and relationship problems can affect young ones as well, threatening their sense of security even when they don’t quite understand what’s going on.

The best action? Get to the bottom of it. If your child can’t articulate what’s bothering him, ask his caregivers or preschool teachers if there’s something that has changed in his daily routine. Problem-solving with your child, finding a way to remove the source of stress and comforting him all can reduce his stress and improve his behavior. Maintaining a consistent schedule at home is also important, including a bedtime routine: reading a book, taking a bath, brushing his teeth—anything that helps him wind down and that he can depend on.

“Even infants experience stress,” adds Dr. Ginsburg. “They cry to get an adult to meet their needs and calm as they suckle. Small children can calm themselves with a snuggle, feeling secure in your presence.” Need an in-the-moment stress reducer? Think bubbles. Sit quietly with your child. Ask her to take in a slow deep breath, then blow out slowly and watch the bubbles float away. Do it again. You’re teaching your child deep breathing—but all she needs to know now is that it’s fun and makes her feel better.