Fred Prouser / Reuters

Since the birth of his two children, Johnny Depp toned down his hard-partying ways. And yet, he remains smoking hot.

Dudes really do clean up their act after they become dads, new research suggests.

Now, the 206 men in this 19-year study may have had more to clean up than most. The researchers recruited them when they were fourth-graders at schools with relatively high rates of delinquency and checked in with them every year from age 12 until 31.

As men enter adulthood, their tendency to commit crime and use tobacco, alcohol and marijuana generally declines, the Oregon State University and University of Houston researchers note in the current issue of the Journal of Marriage and Family.

But the scientists found that fatherhood seemed to provide an extra kick in the pants.

By the end of the study, a little more than two-thirds of the men had fathered children.  While fatherhood at any age didn’t seem to have much of an impact on marijuana use, tobacco use by the dads did fall. Crime and drinking decreased, especially in men who were well into their 20s or older when they became fathers. Whether becoming a first-time dad later in life is tied to similar changes remains to be seen, the authors write.

But women who love bad boys shouldn’t assume that having a baby will fix everything that’s wrong with their guy.

“There was significant variance among the men, however, in these changes following fatherhood,” the authors point out. “Understanding differences in men’s responses to fatherhood demands further consideration.”

Perhaps guys who eventually become dads have a leg up on other men even before a baby enters the picture, says psychiatrist Gail Saltz, a TODAY contributor.

“Obviously, if you’ve chosen to be a father, the notion that you would embrace that by living up to that is not a shock,” Saltz says. “What’s shocking is how many don’t.”

Maybe grandpa can help explain why some new dads straighten up and fly right and some don’t, she says. “When men become parents, it often does evoke in a more immediate way their feelings about their own father.”

Rita Rubin, a contributing writer for msnbc.com and today.com, previously covered medicine for USA Today and U.S. News & World Report. She lives in suburban Washington, D.C., with her husband and two daughters.

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