MDMA (up to 100mg) and alcohol had no interaction on the (3) tests of impulsivity in this double-blind placebo-controlled study (n=18). MDMA alone improved impulse control in the stop-signal task.
“The use of 3,4-methylenedioxymethamphetamine (MDMA) has frequently been associated with increased levels of impulsivity during abstinence. The effects of MDMA on measures of impulsivity, however, have not yet been studied during intoxication. The present study was designed to assess the acute effects of MDMA and alcohol, alone and in combination, on behavioral measures of impulsivity and risk-taking behavior. A total of 18 recreational users of MDMA entered a double-blind placebo-controlled six-way crossover study. The treatments consisted of MDMA 0, 75, and 100 mg with and without alcohol. Alcohol dosing was designed to achieve a peak blood alcohol concentration (BAC) of about 0.06 g/dl during laboratory testing. Laboratory tests of impulsivity were conducted between 1.5 and 2 h post-MDMA and included a stop-signal task, a go/no-go task, and the Iowa gambling task. MDMA decreased stop reaction time in the stop-signal task indicating increased impulse control. Alcohol increased the proportion of commission errors in the stop-signal task and the go/no-go task. Signal detection analyses of alcohol-induced commission errors indicated that this effect may reflect impairment of perceptual or attentive processing rather than an increase of motor impulsivity per se. Performance in the Iowa gambling task was not affected by MDMA and alcohol, but there was a nonsignificant tendency towards improvement following alcohol intake. None of the behavioral measures of impulsivity showed an MDMA × alcohol interaction effect. The lack of interaction indicated that the CNS stimulant effects of MDMA were never sufficient to overcome alcohol-induced impairment of impulse control or risk-taking behavior.”
“In both response inhibition tasks, MDMA did not affect the proportion of commission errors but significantly improved stop reaction time in the stop-signal task. These data indicate that a single dose of MDMA has the potential to stimulate inhibitory motor control in a stop-signal task during intoxication. The pharmacological mechanism underlying improvement in impulse control may be related to acute serotonergic or dopaminergic suppletion following a single dose of MDMA. MDMA is believed to increase 5HT levels during intoxication by stimulating the acute release of 5HT and by blocking the presynaptic reuptake of 5HT.”
This is in contrast to decreased impulse control for those abstinent of MDMA, but who used it heavily before.
“The present data indicates that the CNS-stimulating effects of MDMA do not suffice to overcome alcohol-induced impairment of motor control, which is one of the most common causal factors in vehicle crashes.”