The Rat Park: Addiction and Environmental factors
I recently came across an article in the Walrus Magazine on the Rat Park. Basically a rat park is providing an enriched environment to the rats (both physical and social) as compared to the skinner box and then letting them self-administer the drugs of abuse like morphine. It was found that rats were not prone to addiction to these habit forming drugs , if they lived in an enriched environment.
The problem with the Skinner box experiments, Alexander and his co-researchers suspected, was the box itself. To test that hypothesis, Alexander built an Eden for rats. Rat Park was a plywood enclosure the size of 200 standard cages. There were cedar shavings, boxes, tin cans for hiding and nesting, poles for climbing, and plenty of food. Most important, because rats live in colonies, Rat Park housed sixteen to twenty animals of both sexes.
Rats in Rat Park and control animals in standard laboratory cages had access to two water bottles, one filled with plain water and the other with morphine-laced water. The denizens of Rat Park overwhelmingly preferred plain water to morphine (the test produced statistical confidence levels of over 99.9 percent). Even when Alexander tried to seduce his rats by sweetening the morphine, the ones in Rat Park drank far less than the ones in cages. Only when he added naloxone, which eliminates morphine’s narcotic effects, did the rats in Rat Park start drinking from the water-sugar-morphine bottle. They wanted the sweet water, but not if it made them high.
In a variation he calls “Kicking the Habit,” Alexander gave rats in both environments nothing but morphine-laced water for fifty-seven days, until they were physically dependent on the drug. But as soon as they had a choice between plain water and morphine, the animals in Rat Park switched to plain water more often than the caged rats did, voluntarily putting themselves through the discomfort of withdrawal to do so.
Rat Park showed that a rat’s environment, not the availability of drugs, leads to dependence. In a normal setting, a narcotic is an impediment to what rats typically do: fight, play, forage, mate. But a caged rat can’t do those things. It’s no surprise that a distressed animal with access to narcotics would use them to seek relief.
The article then goes on to address some of the politics behind funding and how Alexander could not secure funding and how he later tried to study the same phenomenon in humans.
Unable to secure funding, Alexander conducted most of his research in the library, where he gathered a mountain of evidence. A survey of Ontario households in 1987, for example, suggested that 95 percent of those who had ever tried cocaine were using it less than once a month. A 1990 survey conducted in the US found that crack cocaine, “the most addictive drug on earth,” was addicting only one user in a hundred. “Naturally, because scholars are scrupulous, I’ve had to try it [morphine] myself,” Alexander says. “It’s no big deal. You’re visibly lightened of pain and anxiety, and that’s mildly pleasant.” But he didn’t experience any urge to try it again. “I just wasn’t interested, and that’s the typical response.”
Then there are the thousands of American soldiers who became heroin addicts during the Vietnam War. In an unrivalled demonstration of the effect of setting, a 1975 survey found that 88 percent of them simply stopped using the drug when they left the war zone. Their experience has been recreated by millions of hospital patients who have received (and become physically dependent on) morphine for severe pain. If opioids are all they’re reputed to be, this practice should have produced legions of addicts. Instead, as researchers have discovered, once patients are no longer in physical distress, they can’t wait to quit the drug, go through the withdrawal period, and get on with their lives. It’s Rat Park’s “Kicking the Habit” experiment carried out on humans, with the same result.
In my view this is an important funding, that has been kept suppressed for a long time, but whose time has come now. We all know the beneficial effects of enriched environments and the harmful effects of stress (even social stress like placed in a lower social dominance hierarchy ) . In a similar experiment with primates it was found that those who were at the top of the social dominance hierarchy did not become addicted while those at the lowest level of hierarchy became addicting to stuff like cocaine and heroin.
Dominant animals had more D2 [dopamine receptor] activity than subordinates, but that was a consequence of their dominance, and not its cause [emphasis added]. Regardless of their D2 activity when kept individually, monkeys that became subordinate showed little change in their PET responses after they had been put into company. In the animals that became dominant, by contrast, D2 activity increased significantly… Like D2 activity, cocaine use was related to social status. Dominant animals found a preferred level, then stuck to it. Subordinates, though, seemed to need bigger and bigger fixes as time went on. That is a classic symptom of addiction… Propensity to addiction, in other words, is not a predisposition of the individual, but the result of social context.
All these data merit a rethink of addiction as a purely biological phenomenon and implores us to take a more environmental approach.
Hat tip: Neuroanthropology blog
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