As with many addictive behaviors and tendencies, drug addiction manifests differently from individual to individual. We wonder why some use substances multiple times and do not become addicted or become dependent but seem to be more “treatable” and less prone to relapse, while others are hooked almost immediately and appear to be in a perpetual tumultuous cycle of drug dependence and withdrawal. A recent study conducted by Benjamin T. Saunders and Terry E Robinson delves into individual differences of drug-seeking and consummatory behavior. Saunders and Robinson examined ties between motivational behavior to obtain cues indicative of a food reward and internally generated cravings from cocaine in rats.
There has been extensive research conducted on pairings of environmental and material drug cues and increased cravings for a drug-of-choice in individuals who suffer from addiction issues. Going to a bar is likely to cause someone with an alcohol addiction jonesing for a drink; trying to stay sober while spending time with a circle of friends an individual with an addiction problem used to engage in substance use with will most likely be incredibly difficult.
This study adds to our perspective of the power of internally engrained drug cues in individuals in perpetual states of dependency and longing for a drug. Rats in the study treat a conditioned stimulus that is predictive of a food reward in different ways: referred to as sign-trackers (ST), certain rats not only came to recognize this stimulus (a lever) as a marker of food, they began to be drawn to the cue itself. Whereas other rats (categorized as goal-trackers (GT)) were motivated to obtain the food reward, ST rats displayed similar behavior towards the cue.
In the second part of the study, cocaine itself acted as a subjective internalized stimuli for further cocaine seeking and desire. ST rats worked harder than GT rats to obtain cocaine and were more likely to have these cravings persist, even when cocaine was made inaccessible to the rats and then reintroduced in a small quantity. This pattern may explain addictive behaviors of drug use in humans: addicts usually will sacrifice a great amount to get a “fix”, the range of rewarding things in their lives narrows to only those related to the drug, and using even one time after a period of sobriety may cause a relapse.
Further investigation into possible neurological differences between ST and GT rats may lead to developments of screenings or medical interventions that may recognize greater individual propensities to addiction and possible treatments for those who suffer from addiction issues. In a society that criminalizes and stigmatizes such individuals, this kind of research can improve general social understandings of addiction by showing that laziness, selfishness, etc. are not causes for addiction and relapse in most individuals, and may highlight larger social and cultural factors of drug issues and addiction.