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Roehrs T, Greenwald M, Roth T. 
“Risk-taking behavior: effects of ethanol, caffeine, and basal sleepiness”. 
Sleep. 2004 Aug 1;27(5):887-93.
OBJECTIVE: This study examined the effects of ethanol, caffeine, and basal sleepiness on a laboratory measure of risk-taking behavior, the Stop Light Task. The aims were to determine whether sleepiness and ethanol degrade psychomotor speed and risky choice and whether caffeine attenuates these effects.

DESIGN: Mixed design with participants chosen for basal level of sleepiness and each assessed under 4 conditions presented in a Latin-square crossover design.

PARTICIPANTS:Thirteen healthy adult volunteers aged 21 to 35 years.

INTERVENTIONS: Participants received ethanol 0.5 g/kg and caffeine placebo, ethanol 0.5 g/kg and caffeine 150 mg, ethanol 0.5 g/kg and caffeine 300 mg, or a dual (ethanol-caffeine) placebo between 9:00 am and 9:30 am.

MEASUREMENTS: The Multiple Sleep Latency Test (MSLT) was used to determine basal level of sleepiness. Subjects completed the Stop Light Task about 60 to 90 minutes after drug administration to assess psychomotor speed and risky choices.

RESULTS: Seven subjects were classified as Alert (MSLT = 12.6 +/- 2.0 minutes) and 6 Sleepy (MSLT = 8.1 +/- 1.0 minutes). Sleepy compared to Alert subjects did not differ in psychomotor speed overall. Ethanol significantly slowed psychomotor speed relative to placebo, and ethanol-caffeine combinations attenuated this effect. Consistent with previous studies using the Stop Light Task, higher response requirements (FR15-FR50) and higher point loss probability (12.5%, 37.5%, 100%) significantly decreased risky choice, across sleepiness and treatment conditions. Alert subjects made "go" (primary measure of risk-taking) choices more often at lower response requirements and less often at higher response requirements, relative to Sleepy subjects. Ethanol did not significantly affect "go" choices but did produce changes in "go" choices as a function of response requirement. Given their more optimal pattern of choice behavior, Alert subjects gained significantly more money than Sleepy subjects; ethanol and caffeine combinations did not significantly affect money earned. CONCLUSIONS: These data suggest that sleepiness moderates risky choice such that Alert subjects have improved choice "acuity." Also, under conditions where risk-taking depends on responding rapidly (like the Stop Light Task), ethanol may also impair responding and caffeine may attenuate this effect.
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