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

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?

This study assesses the residual effects of combined MDMA/THC use, and of THC use alone, upon perceived trajectory of travel.

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 showed impairments in both drug groups, with the MDMA/THC group performing the worst.

The finding that these psychoactive agents adversely affect heading perception, even in recently abstinent users, raises potential concerns about MDMA use and driving ability.