Alcohol demand assessed daily: Validity, variability, and the influence of drinking-related consequences.

BACKGROUND: Alcohol demand, typically assessed at the trait-level, via single administration, reflects individualized alcohol value. We examined correspondence between baseline trait-level and daily brief measures of alcohol demand, and whether demand changes day-to-day in response to recent drinking-related consequences. Understanding whether consequences influence demand fluctuations may provide insight into when demand can be reduced in the context of intervention.
METHODS: Heavy drinking college students (n = 95, age 18-20, 52% female) completed a baseline 14-item alcohol purchase task (APT). Observed demand indices were: intensity (consumption at zero cost), Omax (maximum expenditure), and breakpoint (cost whereby consumption is suppressed to zero). Participants subsequently completed 28 daily reports including a 3-item APT (one item corresponding to each baseline index) and prior day drinking and consequences.
RESULTS: Intraclass correlations revealed within-person variability (i.e., day-to-day change) across daily demand indices. In hierarchical linear models (HLM), each daily demand index was significantly predicted by its corresponding baseline full APT index, when all three baseline indices were entered, suggesting convergent validity of the daily measure. Lower day-level intensity was predicted by more prior day negative consequences, controlling for several day- and person-level variables in HLM. Recent positive consequences did not impact intensity, and daily Omax and breakpoint were not predicted by any tested day- or person-level variables.
CONCLUSIONS: APT indices collected daily map on well to traditional single-administration APT metrics and change in response to recent consequences. Intensity demonstrated the greatest within-person variability, the strongest association with its corresponding full APT index, and theoretically-consistent prediction by negative consequences of drinking.