CHICAGO (AP) – Many teen-rated video contain content that is not listed on the label, including sexual themes, alcohol and profanity, a study found.

Given the results, parents should be aware that popular T-rated video games might include a wide range of unexpected content that could have a negative influence on their children, said Harvard University researchers Kevin Haninger and Kimberly Thompson.

The current voluntary rating system “is not providing complete information to parents,” Haninger said. “In many games there’s content we think parents would care about.”

The authors reviewed labels on all 396 mainstream T-rated video games available as of April 2001, and watched a random sample of 81 games. Violence was listed in content labels on 373 games, or 94 percent; 15 percent were labeled as having sexual themes; 14 percent were labeled for profanity; and 2 percent were labeled for depicting substances such as tobacco or alcohol.

Among the sample the researchers viewed, 20 percent of games with sexual content including partial nudity listed that content on the label; 17 percent of games with profanity listed it on the label; and just 1 percent of games with depictions of tobacco or alcohol listed that on the label.

The study appears in Wednesday’s Journal of the American Medical Association.

The findings point to a need for a clear explanation of the rating process, the researchers said.

Under the rating system used by the Entertainment Software Rating Board, games labeled “T” for teen are deemed suitable for youngsters aged 13 and up and may contain violence, mild or strong language, and/or suggestive themes.

Other ratings include “E” for everyone, “M” for mature and “AO” for adults only.

The system also includes brief content depictors labeled on the game box. These include things like blood and gore, cartoon violence, drug reference and partial nudity.

“Content depictors indicate elements in a game that may have triggered a particular rating and/or may be of interest or concern,” according to the ESRB Web site.

A spokesman for the Entertainment Software Rating Board said he could not comment until seeing the study.