All kids regress for one reason or another: New baby sib. Divorce. Parental abandonment. Anger or anxiety at big change or illness in themselves or someone they love. Abuse of one kind or another. Moving to new home, changing schools, etc.
And regression takes many different forms, often related to the child's age: Toilet "accidents." Significant change in personality (like from sweet to angry, open to guarded, social to withdrawn, etc.). Normal behavior might become very "babyish. They might begin to steal, lie a lot, or hide.
A very intelligent "tween" boy at the shelter seemed co-operative and sociable when I first met him, despite a mild disability. Each week, these positve traits deteriorated a bit more. He started to "played dumb" in group or when I asked him a question. He ignored requests in group. He teased or insulted other kids sometimes.
Most important, when I ate dinner with him and others at the shelter before groups, he switched to extremely babyish behavior when I was around: baby talk, lying on the floor or a bench and acting like a very needy, very small baby.
I ignored most of it or said, "You want to be a baby tonight, huh?" Sometimes this was enough for him to drop the act; sometimes it continued for a few minutes.
His mother was surprised and embarrassed but didn't intervene much when she saw I accepted this immature behavior. I wasn't able to explain to her the possible cause for it--group stories or multiple changes that might have stirred up his anxiety about violence or losses. Unfortunately, he was always around when I wanted to talk to her.
Nonetheless, he did okay in school and within 3 weeks, dropped these babyish behaviors. His cooperation and kindness toward others improved. He liked the new male volunteer, "Coach" and wanted to be "cool" for him. He doesn't like school and is relieved it's over for the year.
His behavior, IMO, is normal and not unusual within the domestic shelter environment. These kids, usually suddenly, lose most of what's important to them. Even when they're prepared for the move, they may have serious reactions to so many changes and losses. Even when the changes are positive.
Time helps, so I always hope that those who regress significantly will stay at the shelter a long time.
They're probably the ones who need a safe home most. Who become babies because that's how they protect themselves and feel safer. And who "grow up" again when they have less fear.
"Normal" children might need the same kind of comfort. Do we give it to them?