Drugs are what cause drug addiction, or so is the story we often hear in the United States.  But what if social conditions mattered as much or more in who used and abused drugs?

 Many anthropologists and other social scientists have shown that social conditions matter, including Phillippe Bourgois, Merrill Singer, and Elliott Currie.  Bourgois’ book In Search of Respect, Singer’s article Why Does Juan Garcia Have A Drinking Problem, and Currie’s Reckoning are powerful testaments to a basic point: Addiction runs along the fault lines of society.

 However, it has been relatively easy for neuroscientists to isolate themselves from that view, and to argue that drugs run along the pharmacological fault lines of the brain, generating terrible problems on their own.  Social conditions are one thing, drugs and brains are another.

 The research by Michael Nader, Morgan Drake and colleagues shows convincingly that social conditions matter, and matter a great deal, at the basic level of the brain.  This same line of research also highlights that individual differences, whether genetic or social, make a difference in addiction.  The trick is that the research is done with monkeys.

 In 2002 Nader, Drake and colleagues published a Nature Neuroscience article entitled “Social dominance in monkeys: Dopamine D2 receptors and cocaine self-administration” (subsequently included in the collection Social Neuroscience: Key Readings).  They measured dopamine activity before introducing lone macaques into social cage situations, where a dominance hierarchy was quickly established.  It was the dominance hierarchy that shaped cocaine self-administration, with significant correlations to dopamine receptor density.  As The Economist summarized the research:
 

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.

 As NIDA Notes quotes Dr. Nader in reviewing the research, “Placement of the monkeys in social groups is modeling two extremes — socially derived stress for the most subordinate monkeys and environmental enrichment for the dominant monkeys.  Although these variables have been studied in other animal models, in our model the stressors and environmental variables were not artificially produced in the lab.”

 In other words, this research supports the work of Bruce Alexander, covered in The Rat Park post, that “led him to conclude that drugs — even such hard drugs as heroin and cocaine — do not cause addiction; the user’s environment does.”  In particular, it shows the role of social structure in shaping biological function, overturning the oft-made assertion that addiction is largely a genetic problem or a “brain disease,” seemingly separate from the nature of people’s everyday lives.

 These everyday lives also shape addiction.  In 2006 research Nader and Drake went on to provide “evidence for a predisposition to self-administer cocaine based on D2 receptor availability, and demonstrate that the brain dopamine system responds rapidly following cocaine exposure. Individual differences in the rate of recovery of D2 receptor function during abstinence were noted.” In other words, (1) individual predispositions matter; (2) using drugs also matters; and (3) ability to recover normal brain function after abstinence also matters.  All three of these things take place in social environments.  As the above research shows, social environments can shape individual predispositions, how much is used, and the impact of social relationships and stress on brain function.

 If this is true in primates, imagine how much more so in humans, who, as Sapolsky notes, have the power “after inventing material technology and the unequal distribution of spoils, to corrosively subordinate [our] have-nots.”  Sapolsky also worked with primate models, and these models can help us argue effectively for what is already obvious to researchers like Bourgois, Singer, Currie and Alexander—the fault lines matter in the terrible social problems we humans make from our own crooked timber.