This isn't the guy sneaking out for a joint now and then when his kids are otherwise occupied. (Unless that occasional indulgence devolves into a five-bong-hit-a-day habit, it doesn't usually have a discernible effect on a man's relationship with his children—not counting a greater mutual interest in dessert.) This is the oldest guy at the club.

There's a dad who appears some mornings at my daughter's elementary school for drop-off. Other days he relies on his full-time nanny to deliver the kids. That's often because he was out the night before, doing coke and maybe taking E. Think about what's actually going on here: Just like the crowds of twentysomethings surrounding him, this guy is getting loaded. But unlike those taut-skinned, child-free partiers, he can't go to a 24-hour diner at 6 a.m. for an omelet and then to bed to sleep it off. He has to go home, pay the sitter, drop a 10-milligram Valium, and hope that in the hours his kids are at school he sobers up enough to be a competent parent when they get back.

Dr. Reef Karim, director of psychiatric services at Wonderland Center in Los Angeles and assistant clinical professor at UCLA, is seeing more and more parents who, as he puts it, "are using in their thirties and forties and don't want to give up that lifestyle."

Statistics show drug use creeping into demographics that previously might have just downed a martini or three after work. The 2005 National Survey on Drug Use found that the portion of 30- to 34-year-olds who had used illicit narcotics in the month before being polled was up to 9.6 percent, while drug use among 22-year-olds had actually decreased since the previous year's survey. In 2003, nearly 3 million Americans 35 and older admitted to having done blow in the past year.

Karim recalls a patient who, along with his wife, "would hire babysitters whenever they knew they were going to take drugs. It was a precautionary measure. They would go to Hollywood Hills after-parties, where they would do coke, pop some E's. Is that okay? No. Is that safer than actually doing E and hanging out with your kids? Yeah. But you know they are going to slip up sooner or later."

Forget the obvious horror stories: Renton and Sick Boy standing over the dead baby in Trainspotting; Jerry Stahl in Permanent Midnight slipping away from a board game with his daughter to shoot up in the bathroom; Courtney Love. Being a heavy user of recreational drugs is inherently selfish. And if there's one thing that becoming a parent robs you of, it's the ability to behave in a purely selfish way without consequences.

I once had an acquaintance, a woman in her thirties, who liked to take, as she put it, "half a pill" (of E) every weekend. When her baby was still sling-size, she didn't hesitate to take her to raves. But as her daughter became less portable and less likely to sleep through eight hours of high-decibel trance music, this woman had to make a difficult choice: leave the child with a babysitter or surrender her little indulgence. She kept partying. Though I listened to her lament her miserable Sundays coming down from E while taking care of a child, she never once concluded that perhaps parenting and getting high don't really mix.

Dr. Stephen Gilman, an addiction psychiatrist in New York City, has also seen a growing number of parents in their thirties and forties using drugs more than occasionally. Not surprisingly, he finds it alarming. "There is less margin for a parent using substances, even if they are doing it recreationally," he says. "There are huge risks of the child experiencing the parent acting irrationally, of the child becoming fearful."

I stopped using drugs three years before my oldest daughter, Esmee, was born. That doesn't mean I can't understand how the idea of spending an evening recapturing that wild dissolution of being 24—not giving a fuck, doing a bunch of coke, and hanging out at after-hours clubs—still appeals. But think about the phone call you might get at 7 a.m. from your child, getting ready for school and wondering where Daddy is. Or even worse, the call from the babysitter saying you have to meet her at the hospital because something is terribly wrong with your 3-year-old. When you think about it that way, the idea of a 40-year-old carrying a skateboard may seem sad, but it isn't tragic.

Are kids and a drug habit mutually exclusive? Share your thoughts in the comment section below.

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