I. AROUSAL

SEX ADDICTION— diagnosing it, treating it, portraying it on-screen—is big business. The number of certified sex-addiction therapists has more than doubled since 2008, according to the International Institute for Trauma and Addiction Professionals. Hookup apps like Tinder (26 million matches per day) and Grindr (1.6 million active daily users) are growing wildly and multiplying, like real-life manifestations of the futuristic smartphone imagined by Gary Shteyngart in Super Sad True Love Story, which rates the "Fuckability" of everyone around you. The movie industry, for its part, has released at least five films on sex addiction in the past five years, six if you count both parts of Lars von Trier’s Nymphomaniac. Forty years ago, the term sex addiction didn’t exist. Today it is thoroughly assimilated into the culture.

But even now, sex addiction seems to exist in parallel realities: one in which millions of people are struggling with it, and another in which it is barely studied and not even clinically recognized. Research has yet to confirm that extreme sexual behavior really is addictive in the same neuroscientific sense that, for instance, habitual heroin use appears to be. For this reason, many clinicians prefer the term hypersexuality, even though they concede that the distinction is mostly semantic. But the practical effects of such uncertainty are enormous. No drugs exist to treat sex addiction; no health care plan specifically covers it; there’s virtually no funding for studies. Eli Coleman, a psychologist and director of the Program in Human Sexuality at the University of Minnesota, estimates that approximately 19 million Americans—5 to 7 percent of the population—are hypersexual. But estimates like this are controversial. "We’re all blind in this field," says UCLA neuroscientist Nicole Prause.

This much is certain: More and more people are seeking treatment. A lot more. In each year over the past decade, the number of groups registered with Sex Addicts Anonymous, one of the nation’s largest twelve-step organizations for sex addiction, has grown by 10 percent. Hollywood is just the latest market to capitalize on this phenomenon, even if filmmakers’ depictions tend to do more harm than good. On-screen, sex addiction tends to be portrayed as glamorous, even fleetingly aspirational—either posey, broody, and existential or chaotically fun in a Warren Beatty-in-the-’70s kind of way.

But no two-hour movie can communicate the relentless patterns of thought that persecute sex addicts. If sex is ordinarily a way of dealing with another person, then sex addiction is a way of dealing with yourself. You act out—you can’t not act out—in order to escape from unbearable feelings: depression, severe ADD, bipolar disorders, the scars of family trauma, profound despair. Most addictions require you to extend yourself in some way—go to a particular place, spend a certain amount of money. Sex addiction does not. The fuel for your disease is all around you, invading your senses. The poet and professor Michael Ryan captures this experience in his unsettling, mesmerizing autobiography, Secret Life: "The substance I used," he writes, "was human beings."

Jacob, age 28

In recovery since 2012

JACOB* IS A COMPUTER PROGRAMMER, and on the morning he greets me at the door of his and his wife’s Seattle-area apartment, he looks as though he’s been up all night wrestling with code. His eyes are bleary behind rimless steel glasses. His face is drained of color. But when I ask him if he’s tired, he says no, just the opposite: "I sleep too well. It’s the only time I’m able to forget everything."

In a wedding photograph on the wall, Jacob holds hands with his wife, Ashley, on a country lane. He smiles hesitantly, his eyes skittering off to one side. If you didn’t know better, you might say he looks like a typical bewildered groom. But what the picture really seems to capture, and perhaps this is why he won’t look directly into the lens, is Jacob at war with himself, trying to erase one terrible thought from his brain: that if his wife knew who he really was—if she knew about the pornography, the explicit online chats, the anonymous sex with other women, with random men—she would get as far away from him as she could.

They have been together for nearly half their lives. They met when they were 16, married in the fall of 2009. But they haven’t had sex since June 2012, haven’t even seen each other naked (except by accident) since he told her he was a sex addict. Almost every night, they separately attend meetings or therapy.

Aside from a few desultory wall treatments, there isn’t much of a female presence in the apartment: Ikea couch and armchair, long desk by the window, computer screens. It may be that Ashley doesn’t go in for decorating. It may also be that she’s still not sure she’s going to stay here. I’d hoped to talk with Ashley today, but she and Jacob have decided against it. I get the impression that her forgiveness may be so provisional that simply facing a reporter’s questions for an hour could undo it.

Four pairs of running shoes, all so worn-out that they’ve lost their shape and turned gray, are lined up inside the front door. In high school, Jacob was all-state three times in cross-country; he still runs six to eight miles every day and competes at least once a month in local events. He has broken this routine only when he’s been lost in the stupor of his addiction.

Jacob grew up devoutly Christian in a remote part of a midwestern state. His father worked the late shift in a factory and typically wasn’t home before eleven at night. As a kid, Jacob was shy and introverted. He dreamed of being an astronaut and walking on Mars, of his toys coming to life and being perfect friends to him.

When I was in third grade, my teenage cousin sexually propositioned me. She wrote me detailed notes about what we would do. I went to a medical encyclopedia to see if all this stuff was real and figured out that it was. We came pretty close to having sex, but I always felt dirty about it. I pushed her away and said, "I can’t do this." So we never did. But it stuck in my mind. I was preoccupied with it for a long time, fantasizing about it. My dad worked a lot, he was never around, and getting that attention felt good.