gambling casino slots
Erik De Castro/Reuters
When it comes to addiction, the brain region everyone talks about is the mesolimbic reward system. Located near regions involved in emotion, pain and decision-making, it’s a motivational circuit that normally encourages humans to pursue evolutionarily beneficial activities, like having sex, drinking water and eating.
It does this by supplying little hits of dopamine and natural opioids when we do things our bodies like.
In the context of drug addiction, people refer to this system as having been “hijacked”—the drug of choice causes such strong reactions that the circuit rewards drug taking above all else and an addiction begins. You know all this already.
But here’s another catch: For some people, the very behaviors the system is designed to reward can become as addictive as any drug. Just ask any problem gambler.
In general, scientists have far less information about these addictive behaviors than they do about cocaine, heroin or alcohol. For starters, it can be hard to determine where normal behavior ends and pathological compulsions begin.
Many scientists don’t even agree on whether people who can’t stop doing something are more similar to heroin addicts or more similar to people with obsessive compulsive disorder (which involves a different, but nearby, set of brain regions).
Don’t despair, though: Researchers are on the case. Dr. Reef Karim, founder of The Control Center, a treatment facility in Beverly Hills that specializes in helping patients kick behavioral problems, wrote a paper in 2012 for the Journal of Psychoactive Drugs detailing which behaviors have the most scientific evidence for being addictive.
Here are five of the leading contenders:

Gambling

slots, gambling, smoking, casino
Carlos Barria/Reuters
It’s like the old chewing gum commercial: Nine out of 10 psychologists agree that if any behavior functions like an addictive drug, this is it. Lifetime prevalence rates for gambling disorder in the US are a little over two percent, and gambling disorder is the only condition that made it into the new section on behavioral addictions in the latest edition of the psychological bible, the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). This is in part because research has found that gambling disorder is similar to substance addiction in brain origin, physiology and treatment.
For example, gambling addicts have reported experiencing “highs” when winning that are similar to the highs reported by cocaine addicts.
They also experience withdrawal symptoms—including insomnia, headaches, upset stomach, loss of appetite, heart palpitations and sweating.
So how does it work? Each time a habitual gambler hits it big, he gets a massive dose of dopamine, making him crave more and bigger wins. When he expects to win and instead loses, dopamine decreases, and the craving gets even stronger.
What’s worse, studies have shown that, when watching a gambling video, gambling addicts have decreased activation in the ventromedial prefrontal cortex (vmPFC)—just like cocaine addicts who watched a video about cocaine. That’s not so good: The vmPFC is an area involved in emotional regulation and risk management.

Compulsive Eating

eating an oreo
Flickr/MariFerSosa
There are several compulsive disorders related to eating—including anorexia and bulimia—and pretty much all of them can wreak havoc on your life. The one that seems to function most like a traditional drug addiction, however, is binge eating—in which people spend excessive amounts of time thinking about or planning eating experiences, and engage in periods of frenzied eating, often past the point of fullness.
This is a massive problem in the US. Current estimates suggest that 3.5 percent of women and two percent of men will have a problem with binge eating disorder at some point in their lives, and that less than half of those people will ever receive treatment.
It’s not hard to see how this particular behavior can become pathological. From an evolutionary standpoint, getting humans to nourish themselves is one of the primary reasons the reward system even exists. Scientists have determined that tasty foods—in particular those high in sugar and fat—activate the dopamine reward circuit the same way drugs do.
And studies on obese people show that they have less of a pleasure-inducing kind of dopamine receptor (called D2) than non-obese people, in the same way that folks who are addicted to drugs have less than those who aren’t addicted.
This D2 reduction may lead obese over eaters to consume even more, in an effort to get the surge of pleasure they expect.
There is also a reduction of activity in nearby inhibitory regions, which means—you guessed it—they’ll also have extra trouble with self-control.

Internet Addiction

student computer laptop studying
AP/Jerry Lai
A recent addition to the hallowed pages of the DSM-5, “Internet gaming disorder” is listed in the section on disorders requiring more study. The extra interest comes mostly because of reports out of Asia of young males becoming so engrossed in their game of choice that they stop eating, commit suicide or neglect their children.
“I’ve had two patients actually fly in from Singapore and China, and they both had extremely strong internet and video game problems,” says Karim. “The problem was that their identity formation was stunted the minute they got into the videogame, so they developed the identity of the character in the game and never developed their own identity. They loved the person they were when they were playing, but they didn’t love themselves.”
According to a 2013 study out of the International Gaming Research Unit (bet you didn’t know there was one of those…) at Nottingham Trent University in England, addiction to video games can be partly associated with “time loss”—that sensation of sitting down to play for an hour then suddenly realizing you’ve played all night and it’s time to go to work.
The games most frequently associated with this kind of time loss are complex, have plots, levels or goals, and can be played with others: A 2007 study from the same group name-checked World of Warcraft more than any other game.

Sex

beyonce H&M
H&M
Yet another evolutionarily obvious one, sex has been shown to increase activity in the reward circuit much like drugs do. But while sex addiction is regular headline-fodder, it has been less extensively studied than some of the other behavioral problems. One difficulty is figuring out what it is about pathological sex that makes it abnormal. A 2006 study out of Sweden, for instance, suggests that it’s not the frequency of sex that’s the problem—very frequent sex with a stable partner actually indicates healthy functioning. Instead, problems appear when people engage in compulsive solitary or impersonal sexual activity—think obsessively watching porn, soliciting prostitutes or exposing oneself to train commuters.
Many of these behaviors have of course been greatly facilitated by the advent of the Internet and the social disconnection it can sometimes encourage.
Though no full-scale nationwide studies on prevalence have been performed, experts estimate that between three and six percent of Americans have had trouble with compulsive sex. Psychiatric studies on people who have come in for treatment for hypersexual disorders have shown deficits in impulse control, judgment and emotional regulation.

Shopping

girl shopping target
Jessica Rinaldi/Reuters
Though scientists quibble over the existence of this one (what would shopping tolerance even look like, for instance?), between two and eight percent of the US population is estimated to have some sort of compulsive relationship with buying. And though the disorder was first described almost a century ago, the constant barrage of marketing emails and online retail sales can’t possibly be helping.
Most people assume that women are the drivers of this particular disorder, but a 2006 study out of Stanford suggests that it affects both genders pretty equally: About six percent of women and 5.5% of men are estimated to shop compulsively. Some scientists have even suggested that addiction to buying may be related to hoarding disorders.
Though researchers aren’t sure which brain system drives this particular behavior, there is evidence that it’s the same old dopamine reward circuit involved in drug addiction: Many people with Parkinson’s disease who are given drugs to increase dopamine develop shopping addiction.
But if you just like to look at clothes online, you’re probably safe: research indicates that window shopping doesn’t count; it’s the process of actually spending the money that causes the dysregulation.

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