The behavioral economics of concurrent drug reinforcers: a review and reanalysis of drug self-administration research.

In economics, goods can function as substitutes, complements, or be independent of one another. These concepts refer to increases, decreases, or no change in the consumption of one item as the price of a second item increases. This review examined whether these economic terms can be used to describe relationships between concurrently available reinforcers in drug self-administration research. Sixteen drug self-administration studies that examined the effects of concurrent reinforcers were identified through a MEDLINE search. Across these studies, the following substances were employed: caffeinated coffee, cocaine, etonitazene, ethanol, heroin, food, methadone, morphine, nicotine cigarettes, pentobarbital, phencyclidine, sucrose and water. These studies were reanalyzed and the results were shown to be consistent with these economic notions. These analyses also showed that relationships among the concurrently available reinforcers were reliable within and across studies, that concurrently available reinforcers can affect each other asymmetrically, and that the relative price may determine the magnitude of effect for substitutes. These findings suggest that these economic concepts may be useful in characterizing the type and magnitude of interactions between concurrently available reinforcers and may suggest potential mechanisms that determine these relationships.