Dramatic Behavior Changes in Toddlers

"Normal" behavior in toddlers varies from one child to another. Some children are shy and others never met a stranger. Most have at least an occasional temper tantrum or melt down when tired. The increasingly independent toddler uses the word “no” rather frequently and may be defiant when you say it to him. The toddler years are a time of major changes, emotionally, physically and socially, but you should see gradual change, not a sudden about-face.

Nightmares and Aggressive Behavior

An occasional bad dream isn’t unusual, but severe nightmares several times a week are not the norm in toddlers. Any child can have an occasional bad day, but if your relatively levelheaded 3 year old is suddenly furiously angry for no obvious reason or begins biting and hitting, odds are there’s something going on. Unfortunately, dramatic behavior changes often occur for some not-so-good reasons. Traumatic stress or physical or sexual abuse can cause abrupt behavior changes in toddlers. If your child suddenly starts acting extremely differently, talk to your pediatrician or family doctor.


Humans react to stressful situations with the “fight or flight” response. Toddlers in a bad situation can feel totally helpless and unable to deal with the physical and emotional reactions except by acting out, becoming irritable or fussy or developing sleep problems, according to the National Child Traumatic Stress Network. A stressed toddler may regress -- she goes back to baby talk, forgets anything she’s learned about potty training or becomes clingy and whiny. These sorts of behaviors are especially likely to occur after a life-threatening occurrence, like a bad auto accident.


Child abuse can cause behavior changes in children, and these behaviors can persist even after the child is in a safe, loving and stable situation. Abuse actually causes changes in the child’s brain, according to an article in the September 2008 issue of “Pediatrics,” especially if the abuse happens during the early years when so much brain development occurs. Children who are abused may withdraw and be unwilling to respond to friendly overtures as a healthy toddler would. Abuse may also cause sleeping problems, anxiety, aggressive behavior or violence toward people or animals.

Sexual Abuse

Sexual abuse, like physical or emotional abuse, can result in behavior problems for toddlers. This is one sort of abuse where the behavior change can literally occur overnight, and parents should consider the behavior a red flag, especially if the toddler suddenly develops an aversion to a particular person, such as a babysitter or relative. A toddler who has been sexually abused may develop any of the signs of stress, such as baby talking or whining. In addition, she may start to complain about pains in the stomach or genitals, or become preoccupied with her body parts. She may suddenly start “playing doctor” with other children.

Trust Your Instincts

You are the best authority on your toddler's behavior. If she is normally a shy, quiet child -- shy and quiet are relative terms with a toddler -- who suddenly becomes mouthy and aggressive, it may just be a developmental stage. If your life-of-the-party toddler abruptly withdraws from the party, there may be a reason other than being tired of the social whirl. Pay attention to that little voice in your head and consult with your doctor, especially if the changes continue or get worse.