Active methamphetamine users discounted outcomes more strongly across future, past, probability and social-distance tasks than comparison participants. The study addresses how outcomes are valued, rather than proving a universal inability to understand consequences.
Yi and colleagues compared active users with nonusing controls using behavioral-economic tasks. Future and past discounting examined value across time; probability discounting examined uncertain rewards; social discounting examined rewards involving other people. These tasks operationalized different forms of psychological distance. This was human observational research, with no randomized methamphetamine dose.
The user group showed greater discounting for all four types when results were collapsed across reward magnitudes. Magnitude-related interactions meant that not every individual subgroup comparison had the same result. Additional assessments did not all differ: the delayed matching-to-sample and social-value-orientation comparisons were nonsignificant. Those null findings should remain visible alongside the discounting results.
A task preference for a nearer or more certain outcome is not equivalent to an inability to comprehend a future event, lack of intent or legal incompetence. The study cannot determine the motives behind a particular financial decision or incident. Group differences in income and other drug exposure also complicate causal attribution, even when examined statistically. Because consumption was not experimentally assigned, the findings cannot separate preexisting preferences from consequences of use. No biological concentration was validated as a measure of psychological horizon. Applied review should examine the actual options, incentives, history and observed behavior. The research supports careful questions about valuation, not diagnosing an individual from a use-history label.
For a separate example of the limits of use-history comparisons, see our current-user driving study. The design and measured outcome determine which conclusions can be carried into an individual case.
Original investigation: doi:10.1097/FBP.0b013e3283564e11.