The Acute Respiratory Distress Syndrome (ARDS): epidemiology, etiology, molecular mechanisms, diagnosis and therapeutic strategies.

A behavioral economic framework of alcohol use posits that alcohol use is a temporally extended pattern of behavior, occurring in contexts where allocation to other response options is available. A primary concept of behavioral economics is demand, which identifies the rewarding value of a commodity as a function of the amount of work an organism expends to meet the cost to obtain it (typically assessed via monetary price, but other costs – e.g., effort, access – exist; ). As the unit price of a commodity increases, consumption of the commodity declines (Hursh et al., 2008). When and to what extent consumption becomes elastic (declines at a sharper slope relative to changes in price) differs across individuals and can be one of several indicators of rewarding value of the commodity (). Hypothetical purchase tasks are based in behavioral economic theory and allow for researchers to pinpoint several indices of demand for commodities (). In single-commodity hypothetical purchase tasks, the unit price of a commodity increases parametrically, and changes in consumption is measured via hypothetical purchase of units of the commodity across prices. For example, the alcohol purchase task (APT; ) involves hypothetical purchase of standard sized alcoholic beverages across a range of prices per beverage. These tasks are useful for several reasons. First, the data collected result in a demand curve with several demand indices (): intensity (consumption at free price), Omax (maximum consumption); Pmax (the price associated with maximum expenditure, or the point at which demand becomes elastic), breakpoint (the final unit price at which any level of consumption is observed), and alpha (“α”; a derived measure that refers to the rate of change in elasticity across the demand curve). While multiple observed demand indices exist, those most robustly associated with reinforcing efficacy of alcohol are intensity and Omax (). Second, purchase tasks are easily adaptable and have been used to examine demand for alcohol, drugs, and non-drug-related items such as food and sexual encounters (; ; ). A less-studied but more ecologically valid adaptation of hypothetical purchase tasks are cross-commodity tasks through which two or more concurrently available commodities are presented (; ). In the most common version of these tasks, the price of one commodity increases while the price of a secondary commodity remains constant, typically at a low unit price. As behaviors exist in complex environments with competing constraints, cross-commodity purchase tasks can more closely mimic the natural environment by examining the relationship between concurrently available alternative commodities. These relationships can be characterized as changes in a reinforcer’s essential value. The availability of alternatives may decrease the value of the initial commodity/reinforcer (substitute), increase its value (complement) or have no impact (independent) (). Most cross-commodity purchase tasks have examined two or more directly consumable commodities in which the units of purchase are clear (). From an intervention and recovery standpoint for hazardous alcohol use, a more appropriate focus for competing commodities may be alternative activities. Engaging in alternative, substance-free activities can be important in promoting durability of treatment goals (). Moreover, engaging in alternative activities may help maintain molar levels of reward in an individual’s environment when alcohol is partially or fully removed from their day-to-day lives, and can help compensate for the loss of other reinforcers (e.g., social reward) that may be associated with reductions in drinking. There are also ethical considerations when overseeing clinical interventions that target alcohol reduction: when removing rewarding contexts from an individual’s environment, it is ethically necessary to supplement with other rewarding activities (BACB Ethics Code).