Gregarious Rats

Thursday, Mar 22, 2012

The only actual evidence for the belief in drug-induced addiction comes 1) from the testimonials of some addicted people who believe that exposure to a drug caused them to "lose control" and 2) from some highly technical research on laboratory animals. These bits of evidence have been embellished in the news media to the point where the belief in drug-induced addiction has acquired the status of an obvious truth that requires no further testing. But the widespread acceptance of this belief is a better demonstration of the power of repetition than of the influence of empirical research, because the great bulk of empirical evidence runs against it.

Albino rats served as subjects and morphine hydrochloride, which is equivalent to heroin, as the experimental drug. Laboratory rats are gregarious, curious, active creatures. Their ancestors, wild Norway rats, are intensely social and hundreds of generations of laboratory breeding have left many social instincts intact. Therefore, it is conceivable that the self-medication hypothesis might provide the most parsimonious explanation for the self-administration of powerful drugs by rats that were raised in isolated metal cages and subjected to surgical implantations in the hands of a eager (but seldom skillful) graduate student followed by being tethered in a self-injection apparatus. The results of self-injection experiments would not show that claim B was true so much as that severely distressed animals, like severely distressed people, will relieve their distress pharmacologically if they can.

My colleagues at Simon Fraser University and I built the most natural environment for rats that we could contrive in the laboratory. "Rat Park", as it came to be called, was airy and spacious, with about 200 times the square footage of a standard laboratory cage. It was also scenic, (with a peaceful British Columbia forest painted on the plywood walls), comfortable (with empty tins, wood scraps, and other desiderata strewn about on the floor), and sociable (with 16-20 rats of both sexes in residence at once).

In the rat cages, the rats’ appetite for morphine was measured by fastening two drinking bottles, one containing a morphine solution and one containing water, on each cage and weighing them daily. In Rat Park, measurement of individual drug consumption was more difficult, since we did not want to disrupt life in the presumably idyllic rodent community. We built a short tunnel opening into Rat Park that was just large enough to accommodate one rat at a time. At the far end of the tunnel, the rats could release a fluid from either of two drop dispensers. One dispenser contained a morphine solution and the other an inert solution. The dispenser recorded how much each rat drank of each fluid.

A number of experiments were performed in this way (for a more detailed summary, see Alexander et al., 1985), all of which indicated that rats living in Rat Park had little appetite for morphine. In some experiments, we forced the rats to consume morphine for weeks before allowing them to choose, so that there could be no doubt that they had developed strong withdrawal symptoms. In other experiments, I made the morphine solution so sickeningly sweet that no rat could resist trying it, but we always found less appetite for morphine in the animals housed in Rat Park. Under some conditions the animals in the cages consumed nearly 20 times as much morphine as the rats in Rat Park. Nothing that we tried instilled a strong appetite for morphine or produced anything that looked like addiction in rats that were housed in a reasonably normal environment.

There was a time when society spoke with unshakable certainty of the terrifying dangers that resulted from even a word of religious heresy and of the incurable consequences of occasional childhood masturbation. At the time, terrifying rhetoric seemed necessary to frighten people away from socially unacceptable behaviours. But the consequences were brutal. Moreover, the scare tactics eventually lost their power anyway. Much the same seems to be occurring now, as both the brutality and the futility of the "War on Drugs" are becoming more and more evident. There are times in history when society is better served by dispassionate information than by manufactured fear.

My hope is that this quick survey of the illusory scientific support for the conventional belief that heroin and cocaine cause addiction can help to show why society should turn away from this unsupported belief. Understanding that there may not be any inherent addictive power in drugs could help to turn us toward a broader, more efficacious formulation of the causes of addiction in our time, and of the huge, dismal saga of tragedy that it produces.

The Myth of Drug-Induced Addiction, Bruce K. Alexander, Department of Psychology, Simon Fraser University,