Rachel Winograd of the University of Missouri analyzed interview data of more than 400 people.
Heavy drinkers at age 25 said they didn't feel immature, but at age 29 and at 35, attitudes changed, Winograd said.
"By age 29 or 30, when most of your peers have settled down and you're still drinking heavily, you may start to view yourself as a sort of Peter Pan of partying, who never fully matured," Winograd said in a statement.
Winograd suggested cutting back on drinking might make one feel more mature.
The study was published in the Journal Alcoholism: Clinical and Experimental Research.