June 2, 2011 -- Children of divorce tend to fall behind in their math and social skills and may not catch up with their peers, a study shows.

Researchers say these difficulties -- along with feelings of anxiety, sadness, and low-self-esteem -- become evident once the divorce proceedings officially begin, not before.

The study is published in the June issue of the American Sociological Review.

"There may be intense marital conflict between divorcing parents and debates about child custody and children of divorce have to move schools, and may fall behind in math and making friends and not catch up," says study researcher Hyun Sik Kim, a PhD candidate in sociology at the University of Wisconsin, Madison.

Of about 3,500 elementary school kids who were followed from kindergarten through fifth grade, children of divorce experienced setbacks in math and social skills and were more prone to feeling anxious, lonely, sad, or tended to have low-self-esteem, compared with their peers whose parents remained married.

These problems first surfaced when the divorce proceedings began and did not get better or worse after it was finalized, the study shows.

Divorce did not seem to affect the children's reading scores or "externalizing" behaviors, including how often they argue, fight, or become angry.

Kim says he was surprised that these setbacks were not seen during the initial pre-divorce stage, which is often filled with strife. But "not all divorces have marital conflict in the pre-divorce stages and perhaps a couple that is likely to divorce may decide not to divorce because they see their children suffering already and think it would make it worse," he says.

The new study looked only at elementary school-aged kids and can't be extrapolated to older or younger children. "Research on divorce suggests that the younger the child is when their parents' divorce, the greater the impact of the divorce," Kim says.

That said, children may be affected differently based on their age at the time of their parents' divorce.

"The most import thing is to have a long conversation with children and closely look at their development," he says. The conversation should begin by making sure the children understand that the divorce is not their fault.