Materialism in children appears to be linked to self-esteem, with their desire for consumer goods mounting as their self-esteem declines, says a U.S. study.

While peer pressure, advertising and poor parenting have all been blamed for kids' seemingly large appetite for toys, clothes and gadgets, University of Minnesota marketing professor Deborah Roedder John maintains that's not what's driving it. She says there has been little academic research backing up such contentions.

In a study published in the December issue of the Journal of Consumer Research, John outlines the results of her research on children in three different age groups.

She and her colleague found materialism increases from age eight or nine to age 12or 13, but then declines by the end of high school when teens are roughly 16 to 18. This mirrors patterns in self-esteem, which instead decreases in early adolescence but increases in late adolescence.

"The level of materialism in teens is directly driven by self-esteem," John said in a news release issuedMonday. "When self-esteem drops as children enter adolescence, materialism peaks. Then by late adolescence, when self-esteem rebounds, their materialism drops."

Citing previous psychological studies, John and co-author Lan Nguyen Chaplin, a marketing professor at the University of Illinois, say the decline of self-esteem in early adolescence is linked to physical changes that make tweens self-conscious. They say in the study that it's also linked to the fact that this is when children move into high school, becoming "the youngest and least important members of the school."

The pair measured materialism by asking 50 children in each age group to answer questions about what makes them happy. Choosing things such as money and brand-name items over non-materialistic things such as being with friends or no homework indicated higher levels of materialism.

The researchers found 12- to 13-year-olds were most likely to choose the materialistic items, while their younger and older cohorts were more likely to choose non-materialistic things.