Zoobiquity (17 page)

And this is precisely why drugs can so brutally derail lives. Ingesting, inhaling, or injecting intoxicants—in doses and concentrations far higher than our bodies were designed to reward us with—overwhelms a system carefully calibrated over millions of years. These substances hijack or ignore altogether our internal Pyxis 3500 mechanisms, removing the need for the animal to input a code, in this case, a behavior, before receiving a chemical dose. Nesse writes, “
Drugs of abuse create a signal in the brain that indicates, falsely, the arrival of a huge fitness benefit.” In other words, pharmaceuticals and street drugs offer a faux fast track to reward—a shortcut to the sensation that we’re doing something beneficial.

This is a critical nuance for understanding addiction. With access to external substances, the animal isn’t required to “work” first—to forage, flee, socialize, or protect. Instead, he goes straight to reward. The chemicals provide a false signal to the animal’s brain that his fitness has improved, although it has not actually changed at all.

Why spend an afternoon in the dangerous and time-consuming task
of foraging for a hundred acorns (or bringing in a hundred new clients) when you could achieve a far more intense reward state with one snort of cocaine? Or, to be less extreme, why go through a half hour of awkward small talk at an office party when a martini or two can trick your brain into thinking you’ve already done some social bonding?

The excessive, seemingly inexplicable behavior of those addicts who forgo the important, life-preserving chores of daily life becomes clearer when viewed this way. Drugs tell users’ brains that they’ve just done an important, fitness-enhancing task—even though they haven’t. Their brain receptors don’t know whether that opioid molecule came from a hash pipe or from having a conversation with a trusted friend. They don’t know whether the dopamine molecule came from a crack spoon or from the rush of getting five phone numbers at a bar or finishing a tough assignment on deadline. The rewarding feelings signal that they
have
gained resources, found mates, and elevated their social status. The awful irony is that these substances so potently imitate these feelings that their users may cease doing the real work of life. Their brains are telling them they already did.

We can condemn addicts and their poor self-control as much as we wish. Ultimately, however, the powerful urge to use and reuse is provided courtesy of honed and inherited brain biology that evolved to maximize an individual’s shot at survival. Seen this way, we’re all born addicts. That’s what “motivates” creatures to do important things.

And that’s why Pyxis 3500 machines stand sentry throughout my hospital. They restrict access. As David Sack, the CEO of the drug-rehab program Promises, told me, “
You can’t become addicted to a drug you don’t have access to.”

Putting synthetic and plant-derived drugs into our bodies circumvents the personal lockboxes in our brains. But the stashes of natural drugs are still in there. And, as we’ve seen, the codes to releasing them are elemental behaviors. This reveals an interesting possibility. Even if an animal doesn’t have access to external sources of drugs, there may be another way to hack into the internal stores: by punching in code after code … of unnecessary but reward-producing behaviors. Maybe addiction can be activated by things we
do
, almost as effectively as the substances we
take
.

• • •

As a cardiologist, I mostly encounter substance addictions as they relate to a patient’s heart health. But in the late 1980s, I was training to become a psychiatrist and began treating a patient for depression and anxiety. He was handsome and a meticulous dresser. At our weekly sessions he was unfailingly polite and charming, which I interpreted as an openness to the therapeutic process.

At our first meeting I learned the main reason for his anxiety: he was cheating on his wife. Soon I learned that he was cheating on the mistress, too—with her best friend. While maintaining regular relationships with all three women, he was also having frequent one-night stands. As he described the stress and anxiety of juggling each week’s sexual appointments, he explained his utter inability to stop doing it. I could sense his excitement about what he was doing—the danger of sleeping around, of hiding it from his family, the thrill of getting away with it. As his psychiatrist, I thought it all just sounded dangerous. He was risking his marriage, his relationship with his child, and his career (the mistress was a subordinate at work). After several months, he quit coming to therapy; he continued his risky behavior and eventually lost his job and his wife.

At that time, psychiatry had a primary approach to treatment: psychodynamic psychotherapy. The basic premise of this method is that our adult selves are formed in large part by our childhood experiences. The entire time I was treating this patient, my professional assumption was that his inability to have a stable sexual relationship with his wife stemmed primarily and perhaps exclusively from attachment issues connected to early childhood traumas. My supervisors confirmed the diagnosis and supported my treatment plan, so I spent many sessions probing his early years, looking for reasons to explain his promiscuous and risky behavior.

Thinking about it twenty-five years later, I realize that my understanding of his reckless sexual behavior was incomplete. The field has now advanced to recognize that early experiences do actively shape genes and the brain, laying the groundwork for susceptibility to addiction later in life. But what I had missed then was the fact that my patient was addicted to the neurochemicals provided to him through his sexual pattern: the spike of thrill-danger-novelty dopamine and perhaps also the feel-good payoff of sex itself. Nowadays he would probably be referred to a sex-addiction program. But that never occurred to me then.
The brain-disease theory of alcoholism was only just emerging at the time. That behaviors like sex or shopping or overeating could be put in the same category as a substance addiction wasn’t part of the medical vocabulary. Even today, addictions to the things a person does, instead of the substances he takes, are not completely understood. The debate over whether or not they’re “real” addictions divides doctors within and outside the addiction field.

I have to confess that, until recently, I, too, was extremely skeptical. You’re “addicted” to buying shoes. Really? Can’t stop eating candy corn? Feel physical withdrawal pains when separated from your pornography or video game? Uh-huh. The model of substance addiction as a brain disease made sense to me, but until recently, applying the term “addiction” to behaviors seemed sloppy—a “no-fault,” feel-good copout, a lazy, twentieth-century inability to break bad habits. It’s not me, Your Honor. It’s my
disease
.

However, spending the past several years trying to understand my human patients through a veterinary perspective has led me to a different view and a surprising hypothesis: substance addiction and behavioral addiction
are
linked. And their common language is in the shared neurocircuitry that rewards fitness-promoting behaviors.

When you look at the most-often-treated behavioral addictions from an evolutionary perspective, they are exceedingly fitness enhancing. Sex. Binge eating. Exercise. Working. It’s hard to imagine that “in nature” or when tested by natural selection, those behaviors would produce many downsides, even when taken to extremes.

Gambling and compulsive shopping—although they’re human variants—work on the same neural pathways as two extremely beneficial animal activities: foraging and hunting. These involve focused and concerted effort and expenditure of energy with a specific goal of gaining resources, typically food but sometimes shelter or nesting materials. Neurochemical rewards reinforce this positive behavior in animals. As Panksepp puts it, “
Every mammal has a system in the brain to look for resources.”

By following the neurobiology, we can see that gambling is foraging taken to an extreme, where food has been replaced by a financial payoff. Although food and money are certainly rewards in themselves, the true payoff—the addictive part—is the neurochemical mix associated with
seeking and risk-taking. Behavior produces a reward that creates dependence, just as external chemicals do.

Connecting brain-rewarding behaviors to increased survival also allowed me to rethink technological “addictions” like video gaming, e-mail, and social networking. The executive who jokes that she’s addicted to her BlackBerry probably doesn’t think she needs a twelve-step program to quell her itchy thumbs. But many of us find the urge to check that little screen irresistible—even during an important meeting or when we’re behind the wheel. Our smartphones, Facebook pages, and Twitter feeds profoundly combine the things that matter most to animals competing to survive: a social network, access to mates, and information about predatory threats. But like drugs, these devices provide the hit without the work. We get a dopamine squirt without seeking a tangible resource. We may get a lovely opiate flood of feeling part of a herd, without the inconvenience of actual herd mates.

Veterinarians I interviewed were reluctant to apply the word “addiction” to animals. As they pointed out, pets generally do not, on their own accord, get hooked on drugs or alcohol.

But there is one thing they seem to crave: reward. It can be as simple as a pat on the head and a murmured “Good boy.” A morsel of frozen liver or mouthful of oats. A tummy rub.

Do a behavior, get a reward. Rewards in the form of food or praise have long been used by animal trainers to produce certain predictable behaviors.
As Gary Wilson, a professor and trainer at the Exotic Animal Training and Management Program at Moorpark College in California, told me, external treats in the form of food and congratulatory sounds are in effect bridges to the animal’s brain. They pair the feel-good neurochemicals produced by anticipation of nutrients with desired behaviors.
^b

Seen this way, the unrecognized goal of some animal training may be to create a kind of behavioral addiction, as animals learn to associate the pleasure of reward with new behaviors.
David J. Linden, a professor of neuroscience at Johns Hopkins University and author of
The Compass of Pleasure
, connects this pleasure of learning and training in humans to the neurobiology of other addictions.

He notes that learning, along with behaviors such as gambling, shopping, and sex, “evoke neural signals that converge on a small group of interconnected brain areas called the medial forebrain pleasure circuit.” Successful dog training creates what we could call a learning addiction, driven by pleasure circuits. Linden notes that these circuits “can also be co-opted by artificial activators like cocaine or nicotine or heroin or alcohol.”

Human medicine has only recently started to regard chemical dependency as a physical and chronic illness requiring ongoing (perhaps lifelong) care, rather than a condition (like an infection) that we can treat, cure, and quickly put behind us. Understanding the evolutionary origins of addiction can improve how we care for this disease. It may help us be more compassionate to users and addicts and can help us understand that substance use in animals of all kinds is an attempt to get a little more of what we spend our lives seeking.

If you exposed a hundred people to a carcinogen, they wouldn’t all get cancer. It’s the same thing with drugs. Expose a hundred animals to a chemical molecule, and they’re not all going to get addicted to it. Not all cocker spaniels become toad lickers. Not every monkey steals cocktails or wants to drink one every day. Only some wallabies jump the fence to eat opium poppy sap.

The biological term for these differences within populations is “heterogeneity.” What heterogeneity means in terms of addiction is that each person, each animal, has a slightly different response to each chemical. An abundance of research backs this up: there’s a strong genetic basis for susceptibility to addiction. Recently, families with histories of substance abuse have started educating their children about their particular inborn vulnerabilities. But environmental factors, from the climate in our mother’s uterus to the food we eat and the pathogens we encounter, also play key roles in who becomes an addict. It’s becoming clearer to scientists
that what you eat, where you live, the work you do, and even how you were parented can change how your genes are expressed. The emerging field of epigenetics considers what happens to our personal genetic code when it meets the real world. It explains why nature/nurture is not a divide but, rather, an endless feedback loop.

Genes give an individual high school sophomore a predetermined potential to become addicted to alcohol or drugs. But when and how he encounters those chemical molecules will create the epigenetic effect. For one teen, a Friday night, postgame first exposure to, say, marijuana can activate neural responses that will make cannabis a gateway drug for future use. For that teen’s best friend, that first toke might be just another moment in an ordinary get-together at a friend’s house, a teenage dalliance that he’ll laugh about in a self-deprecating way later in life. Same party; same drug; two different life outcomes. If either teen had encountered that substance as an older adult or as a younger child, again, the outcome might be different.

Like many humans, some nonhuman animals can enjoy the pleasures of substances without apparent adverse effects. The Malaysian pen-tailed tree shrew imbibes copious volumes of fermented palm nectar without observably diminished reflexes or impaired coordination. Zenyatta, a multilaureled and now retired racehorse, traditionally guzzled a Guinness after every race and went on to win the next one.

Heterogeneity stocks every animal’s lockbox with different supplies of drugs. Epigenetics calibrates the codes. Those codes are set and changed throughout our lives. But an important period of code setting occurs in childhood—infancy through adolescence. Human and animal data both suggest that the younger the animal is at first exposure to an external drug, the more likely it is to become addicted and responsive to that drug in the future.