Do drugs cause addiction? While this seems like a simple question that should come with a simple answer, the reality is much more complex.
Of course, a person cannot become addicted to drugs without ever taking drugs – that is a given. From this, it does seem logical to support the idea that drugs cause addiction. Perhaps a better question is this: Does everyone who uses drugs become addicted? While this is a similar question, now the answer seems a bit murkier. I bet most people can think of someone they know who can skip morning caffeine without care, or who quit smoking easily, or who drinks regularly but doesn’t mind abstaining, or who took pain meds post-surgery for many days but did not become dependent. At minimum, I’m sure most have heard “addictive personality” being tossed around to describe someone who seems to become easily entrapped in maladaptive patterns of behavior. So, on the surface at least it might not be entirely accurate to assume that drugs are causing addiction. Another related question is this: For someone who never uses drugs, are they free from addiction? Might they still display addictive-type use of other reinforcers such as food, video games, cell phones?
On the issue of whether drugs cause addiction, over the years the public and scholarly opinion pendulum has swung between a hard yes and a firm no and everywhere between. Some propose that the chemical properties of certain substances lead one down a straight causal pathway toward dependence. This was particularly true 40+ years ago. America’s War on Drugs is based on this general premise – that drugs themselves are evil and need to be removed from the streets. On the other end of the spectrum, some propose that a person’s environment and general life circumstances either provide a person with a vulnerability toward or a protection from addiction, and that the properties of the drug itself (or another reinforcer type) is less important. More recent research has been investigating how genetic or epigenetic variables can provide an important confluence between drugs and environment.
I recently saw an article reminding me of a series of studies done in the 1970’s that shed some light this general question. The researchers wanted to examine whether different groups of rats would be equally likely to self-administer an opioid drug (morphine) based on their living circumstances. For the experiment, one group of rats lived social isolation – housed singularly in cages with no enrichment devices. (Housing animals alone is standard practice for many laboratory studies, done to control for random sources of variance that could mar the results.) Another group lived together in a social area filled with different toys and items for them to explore and climb upon. The researchers dubbed this second area “Rat Park”.
The researchers conducted several iterations of the experiment with the general method being that rats were given the opportunity to drink two different substances: water, or a mixture of morphine and sugar water. They found that when the morphine solution was sufficiently spiked with sugar, the rats consumed the drug substance. However, rats who were housed alone consumed significantly more of the drug solution than did the rats living in enriched rat park. Researchers concluded – and hold the opinion to this day – that addictive behavior is not rigidly caused by drugs nor is the simple availability of drugs enough to encourage drug use. Something about the enriched social environment protects from the lure of drugs. Or something about relative isolation encourages it.
Now, I wish the story could just end there in an uncomplicated manner. But science is far too exciting for things to be simply proven true. When I dug into the literature more, I found that the same and other researchers tried to investigate what exactly is it about Rat Park that protects individuals from substance use. While doing so, at times they produced inconsistent results and several failures to replicate. Yet – the results sometimes are replicated. Clearly there is more to this story. Despite the inconsistent research findings, I was surprised by the upsurge of recent articles referencing Rat Park. Heck, here I am jumping on the bandwagon and discussing it. What I’m taking away from it is that there seems to be something about this line of research that resonates with people nowadays, whereas it was viewed with more skeptical caution in decades prior.
The original researcher Bruce Alexander admits that “the Rat Park housing effect cannot be taken to be as robust as it originally appeared to be.” (Peele, S., 1985). Despite this, Alexander strongly maintains that it is false to believe that there are inherently addictive or irresistible drugs. Drugs do not cause addiction.
This view – that we need to be more mindful of a person’s environment and context to fully appreciate why they behave the way they do – is more aligned with the current zeitgeist’s pendulum. While environmental circumstances might not account for everything, simple availability of drugs cannot either.
There are a few major research domains in behavior analysis that have shed light on the relative impact of the environment on an individual’s choice behavior, two of which I will cover more in coming blogs. One is delay discounting, which describes how people devalue rewards as they are delayed into the future. Individuals who more steeply discount delayed outcomes are thought to be more impulsive. Indeed, these individuals are also more likely to be diagnosed with a clinically impulsive disorder, such as substance abuse. Interestingly, several researchers examining discounting in rats have found that group housing and social enrichment (similar to that found in Rat Park) can decrease impulsivity. As you might imagine, there is significant research and public interest in better understanding how we might be able to lower discounting to potentially impact behavior patterns like substance use.
A second area of research is a broad quantitative model of individual choice behavior called “the matching law”. According to the matching law, individual choices are influenced by outcomes. Sounds simple, right? But it’s not merely the outcome produced by that particular behavior; rather that outcome relative to all other options a person has. Thus, our choices – what we do at any given moment – can only be understood by evaluating how much we stand to gain (or not lose) from doing one thing as compared to the combined gain/loss-avoidance value of other options we have. By this view, it makes complete sense why rats living in isolation with nothing much to do consumed more drugs than those living the relatively lux rat park life. The same substance is simply more valuable to certain individuals, relatively speaking. Understanding the matching law has allowed researchers to tailor better treatments for substance abuse. And importantly, understanding the matching law can impact how we view drug addiction – not as a moral failing, but rather a rational choice given the circumstances.