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When the party is over….

Investigating the effects of alcohol, THC and MDMA on simulator driving performance
PhD ceremony:dr. J.L. (Janet) Veldstra
When:December 11, 2014
Supervisor:prof. dr. K.A. (Karel) Brookhuis
Co-supervisor:prof. dr. D. (Dick) de Waard
Where:Academy building RUG
Faculty:Behavioural and Social Sciences
When the party is over….

It sounds so familiar and logic: driving under the influence is dangerous. Still drivers are regularly found to be driving under the influence. Is it really that dangerous? When taking ecstasy you feel pretty clear minded and maybe it could actually help you overcome the negative effects of alcohol? Also, when you are used to taking a certain substance you are familiar with ways to compensate for the impairing effects, right? So driving should be fine? In this thesis we investigated these and other questions by giving participants oral THC or MDMA -the latter both alone and combined with alcohol- and asked them to drive in our driving simulator.

We found that MDMA, when taken in the controlled setting of the lab, did not influence driving abilities negatively.  We also found that on average MDMA indeed reduced alcohol impairing effects somewhat, but these effects were not enough to overcome the effects of alcohol completely. It was also clear that individuals differed greatly in the effect the combination of drugs had on them. We therefore conclude that taking MDMA and alcohol do not go together with driving even though it often feels as if one can.

We replicated earlier findings that THC negatively influences driving performance. This was the case for both drivers who were used to THC because they were regular cannabis users and drivers who were not as used to the drug since they only used THC on an occasional basis. Even so, the latter group did perform somewhat worse than the first. We also found that drivers indeed compensate for the impairing effects of THC by reducing speed more when they feel higher. But these compensational efforts were insufficient to overcome the effects THC has on driving ability.