When college students come home for the holidays after a few months of independent living, the entire family has to adjust to a different person walking in the door, says a Purdue University expert.

"Every time a student goes off to college, the family system changes," says Charles "Chuck" Calahan, assistant clinical professor of family studies. "Families need to revisit their relationships to adjust to the new dynamics."

The process of separation starts when students leave home in the fall.

"I see it every fall with the new students walking across campus," said Calahan. "You can see it in nonverbal behavior, when the student is walking 10 or 12 steps in front of the parents, anxiously waiting for them to leave so the student can be on his or her own."

When students are at school, they stay out later, but when they return home, they find different rules, Calahan said. Naturally, they rebel.

"Parents interpret that as a rejection, and they feel like they've lost their child," said Calahan. "It's a healthy process, but it feels awful."

He compared the process to growing pains because both parent and child are becoming new, better and different adults.

Parents are going through an important process of turning loose the next generation, and Calahan advised them to maintain communication and learn to negotiate.

"All these changes can put a damper on the holidays," said Calahan. "The kids need to be wise and mature beyond their years and realize their parents are acting out of love."