At the end of the 1970s, Bruce Alexander published a series of clinical studies known as the rat park experiments. The studies compared two groups of rats, all pre-addicted to morphine. The first group lived separately in isolated cages, and the second group lived together in a rat colony where they could play, have sex, and socialize.
Alexander offered the rats a choice between water and a morphine solution. He found that the rats living together in the colony drank significantly less morphine than those living alone in isolation.
Alexander published the rat park experiments near the beginning of the war on drugs in the United States. The war on drugs was a hugely expensive and largely ineffective attempt to reduce the drug trade through harsh legal penalties and punitive policies. The consensus was that the substance itself caused addiction and that addiction could only be reduced by removing the substance from society.
Alexander argued that his experiments showed that environmental factors were the primary cause of addiction, and consequently, fighting drug addiction should involve nurturing environments where people choose not to take addictive drugs rather than simply punishing those who deal them.
Subsequent studies have supported these conclusions. A 1992 study that isolated mice for different periods of time before offering them the choice between morphine and water found that the length of time for which mice were isolated directly correlated with the amount of morphine they chose to drink.
Similarly, a 2010 study on rats found that as little as sixty minutes of daily social interaction with another rat was enough to bring their morphine consumption down to the same level as the colony rats. It implies that social factors in the environment may be especially important in preventing or treating addiction.
It is, however, important not to draw firm or specific conclusions from these experiments alone - the rat park experiments have several limitations.
Firstly, they are studies on rats, not humans, and there are, of course, many differences between them and us. Secondly, the number of rats in each experiment was small, and the results were only generated under very specific conditions. Also, some subsequent studies with different kinds of rats failed to replicate the same results.
Given this, it would be wrong to conclude from the experiments that we could solve drug addiction crises just by providing certain social settings for people to live in or that environmental conditions are the only factors at play. But the experiments do suggest we should consider environmental factors in our research on addiction treatment methods, prevention programs, and policies impacting drugs and crime.
Other scientific research and observations support the idea that environmental conditions are important risk factors for developing addiction and may be key to treating it.
For example, by the end of the Vietnam War, many US soldiers were addicted to opioids. However, when they returned to their hometowns, they found that quitting was a relatively easy process. Whether this was because of the absence of triggers, lack of availability of drugs, or other reasons, it seemed the change in environment made a big difference.
Research into addiction treatment methods has also found that environmental factors - in particular supportive social networks - can be crucial in the addiction recovery process. Support groups like 12-steps meetings, where people in recovery help one another overcome addiction, are proven to help people maintain abstinence from drugs and alcohol in the long term.
Equally, environmental factors also affect the risk of developing an addiction in the first place. Studies have found, for example, that exposure to traumatic events during childhood increases the likelihood of developing an opioid dependency.
Like the rat park experiments, these findings point to the role of environmental factors in drug addiction. This does not mean, however, that they are the only relevant factors. Brain chemistry, genetics, and the substance itself may also play a role, and it is important to consider all these elements together when studying addiction.