Cognitive function and mood in MDMA/THC users, THC users and non-drug using controls.

Repeated ecstasy (MDMA) use is reported to impair cognition and cause increased feelings of depression and anxiety. Yet, many relevant studies have failed to control for use of drugs other than MDMA, especially marijuana (THC). To address these confounding effects we compared behavioural performance of 11 MDMA/THC users, 15 THC users and 15 non-drug users matched for age and intellect. We tested the hypothesis that reported feelings of depression and anxiety and cognitive impairment (memory, executive function and decision making) are more severe in MDMA/THC users than in THC users. MDMA/THC users reported more intense feelings of depression and anxiety than THC users and non-drug users. Memory function was impaired in both groups of drug users. MDMA/THC users showed slower psychomotor speed and less mental flexibility than non-drug users. THC users exhibited less mental flexibility and performed worse on the decision making task compared to non-drug users but these functions were similar to those in MDMA/THC users. It was concluded that MDMA use is associated with increased feelings of depression and anxiety compared to THC users and non-drug users. THC users were impaired in some cognitive abilities to the same degree as MDMA/THC users, suggesting that some cognitive impairment attributed to MDMA is more likely due to concurrent THC use.

Impaired perception of self-motion (heading) in abstinent ecstasy and marijuana users.

RATIONALE: Illicit drug use can increase driver crash risk due to loss of control over vehicle trajectory. This study asks, does recreational use of +/-3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) and tetrahydrocannabinol (THC; marijuana) impair cognitive processes that help direct our safe movement through the world? OBJECTIVE: This study assesses the residual effects of combined MDMA/THC use, and of THC use alone, upon perceived trajectory of travel. METHODS: Perception of self-motion, or heading, from optical flow patterns was assessed using stimuli comprising random dot ground planes presented at three different densities and eight heading angles (1, 2, 4 and 8 degrees to the left or right). On each trial, subjects reported if direction of travel was to the left or the right. RESULTS: Results showed impairments in both drug groups, with the MDMA/THC group performing the worst. CONCLUSIONS: The finding that these psychoactive agents adversely affect heading perception, even in recently abstinent users, raises potential concerns about MDMA use and driving ability.

Dissociable effects of a single dose of ecstasy (MDMA) on psychomotor skills and attentional performance.

Ecstasy (3,4-methylenedioxymethamphetamine, MDMA) is a psychoactive recreational drug widely used by young people visiting dance parties, and has been associated with poor cognitive function. The current study assessed the influence of a single dose of MDMA 75 mg and alcohol 0.5 g/kg on cognition, psychomotor performance and driving-related task performance. Twelve healthy recreational ecstasy users participated in an experimental study conducted according to a double-blind, double-dummy, placebo-controlled three-way cross-over design. MDMA improved psychomotor performance, such as movement speed and tracking performance in a single task, as well as in a divided attention task. MDMA impaired the ability to predict object movement under divided attention. However, the inability to accurately predict object movement after MDMA may indicate impairment of particular performance skills relevant to driving. There was no effect of MDMA on visual search, planning or retrieval from semantic memory.

The causal role of self-awareness in blushing-anxious, socially-anxious and social phobics individuals.

This study examined the effect of attentional focus on social anxiety in three groups of subjects: high versus low blushing-anxious participants (n=48); high versus low socially anxious participants (n=60); and social phobic patients compared to patients with other anxiety disorders (n=48). Participants were asked to imagine two series of social situations, in which the hero was in the centre of others' attention. In the first series of stories, the type of feedback from the audience (positive, negative and neutral) and the direction of attention of the hero (self- versus task-focused) were manipulated, and in the second series of stories, the presence or absence of blushing and the direction of attention of the hero were manipulated. In line with the expectations, self-focused attention (SFA) led to more social anxiety than task-focused attention (TFA) in all the three experiments, and high blushing-anxious, socially anxious, and social phobic groups reported higher levels of self-awareness than their low-anxious comparison groups. No evidence was found for the idea that self-focusing is specifically detrimental for participants who are already socially anxious, blushing-anxious, or socially phobic. Also, attentional focus did not interact with the valence of social feedback. Finally, results provided some support for the hypothesis that fear of blushing is mediated by self-focusing. The results suggest that irrespective of trait social anxiety, and irrespective of the outcome of a social situation (positive, neutral or negative), SFA increases state social anxiety, or TFA decreases state social anxiety.

Visual search and urban driving under the influence of marijuana and alcohol.

The purpose of the present study was to assess the effects of low doses of marijuana and alcohol, and their combination, on visual search at intersections and on general driving proficiency in the City Driving Test. Sixteen recreational users of alcohol and marijuana (eight males and eight females) were treated with these substances or placebo according to a balanced, 4-way, cross-over, observer- and subject-blind design. On separate evenings, subjects received weight-calibrated doses of THC, alcohol or placebo in each of the following treatment conditions: alcohol placebo + THC placebo, alcohol + THC placebo, THC 100 &mgr;g/kg + alcohol placebo, THC 100 &mgr;g/kg + alcohol. Alcohol doses administered were sufficient for achieving a blood alcohol concentration (BAC) of about 0.05 g/dl. Initial drinking preceded smoking by one hour. The City Driving Test commenced 15 minutes after smoking and lasted 45 minutes. The test was conducted over a fixed route within the city limits of Maastricht. An eye movement recording system was mounted on each subject's head for providing relative frequency measures of appropriate visual search at intersections. General driving quality was rated by a licensed driving instructor on a shortened version of the Royal Dutch Tourist Association's Driving Proficiency Test. After placebo treatment subjects searched for traffic approaching from side streets on the right in 84% of all cases. Visual search frequency in these subjects did not change when they were treated with alcohol or marijuana alone. However, when treated with the combination of alcohol and marijuana, the frequency of visual search dropped by 3%. Performance as rated on the Driving Proficiency Scale did not differ between treatments. It was concluded that the effects of low doses of THC (100 &mgr;g/kg) and alcohol (BAC < 0.05 g/dl) on higher-level driving skills as measured in the present study are minimal. Copyright 2001 John Wiley & Sons, Ltd.