Acute and delayed effects of MDMA intoxication on false memories in a legal context

Background summary

False memories refer to memories of events/details that did not actually occur
(Otgaar, Howe, Brackmann, & Smeets, 2016). False memories frequently occur
spontaneously but can also be elicited through suggestive pressure. Legal cases have shown that eyewitnesses and innocent suspects can falsely remember to have seen non-existing details of a crime or falsely confess to have committed a
crime due to suggestive interrogation tactics of the police. Such false
memories can lead to wrongful convictions. Moreover, eyewitnesses and suspects
are often under influence of drugs such as MDMA while no knowledge base exists
whether their drugged state makes them more sensitive to spontaneous or
suggestion-based false memories. From a practical perspective, examining this
issue is highly relevant as MDMA is the second most widely used illicit drug in
the world, and is strongly prevalent in the Netherlands. In the courtroom,
eyewitness and suspect statements are seen as highly valuable evidence, thus
their reliability is important.

Study objective

Primary Objective: to assess the immediate and delayed effects of THC on true
and false memories in a legal context (i.e., on eyewitness and offender
statements).
Secondary Objective(s): to link drug-induced false memory effects to
dissociation
Tertiary objective: to assess functional connectivity in a subset of
participants in both treatment and control conditions in order to add to a
database of drug-induced changes in the brain, as well as link fMRI data to
false memory effects

Study design

The study will be conducted according to a double-blind, placebo-controlled, 2
(Group: Treatment vs. Control) by 2 (Time 1 vs. Time 2) crossover
mixed design with Group as a between-subjects factor. Occasional (N=64)
MDMA/ecstasy users will receive single doses of MDMA (75mg) and placebo according to a double-blind design in which they will be exposed to either an eyewitness scenario (Study 1a) or a perpetrator scenario (Study 1b). Each participant will be allocated to 1 of 2 groups (n=32 each) that receive eyewitness and perpetrator virtual reality scenarios during opposing treatment conditions. Groups will be matched according to sex, education and age. The major advantage of this approach is that participants will only be exposed once to each scenario (i.e. to exclude carryover and learning effects) while participating in both studies.

Intervention

i

Placebo (bitter lemon drink) and MDMA (75mg capsules dissolved in bitter lemon drink)

Study burden and risks

The participants will be administered placebo and MDMA in a crossover study.
They will view two different virtual reality mock crimes on separate testing
days, and subsequently their memory will be assessed. For more information see the research protocol.