None listed
Conditions
Brief summary
Understanding the effect of intoxication on witnesses is important to the legal system, but key gaps remain. While research on alcohol and memory is advancing (e.g., Jores et al., 2019), little is known about other substances in an eyewitness context. There is minimal research on amphetamines and event memory, and no known research on amphetamines and face recognition in a line-up context. Further gaps remain around dosage, timing, and expectancy effects. Many crimes are distressing, yet minimal research has explored intoxication and memory in the context of a distressing event. The role of stress warrants particular attention given that stress hormones are released during amphetamine use, and it remains unclear whether alcohol attenuates the stress response, whether stress alters alcohol metabolism, and how either may interact with memory. Critically, no known research has examined the combined effects of alcohol and amphetamine intoxication on eyewitness memory, despite the relevance of polydrug use to real-world forensic contexts. Study hypotheses: alcohol is anticipated to impair memory completeness but not accuracy, while dexamfetamine may enhance memory relative to placebo. The polysubstance condition (dexamfetamine + alcohol) is expected to produce differential effects on memory relative to either substance alone. An exploratory aim is to investigate whether acute stress moderates drug response and subsequently impacts memory.
Interventions
This trial uses a parallel-group between-subjects design where each participant will attend 1 session. Participants will be randomised to receive one of four conditions. Comparison will be made between alcohol (positive control, to an approximate blood alcohol concentration [BAC] of 0.08% at 1 hour; beverage volume is individually calculated based on participant body weight and biological sex using the Widmark Formula, a standard BAC pharmacokinetic formula) and placebo (negative control) with t
This trial uses a parallel-group between-subjects design where each participant will attend 1 session. Participants will be randomised to receive one of four conditions. Comparison will be made between alcohol (positive control, to an approximate blood alcohol concentration [BAC] of 0.08% at 1 hour; beverage volume is individually calculated based on participant body weight and biological sex using the Widmark Formula, a standard BAC pharmacokinetic formula) and placebo (negative control) with the substance of interest dexamfetamine (20mg oral tablet), and their combination (polysubstance condition), across four arms: Arm 1: dexamfetamine tablets (20mg) + placebo drink Arm 2: placebo tablets + alcohol drink (variable volume; ~0.08% BAC) Arm 3: dexamfetamine tablets (20mg) + alcohol drink (variable volume; ~0.08% BAC) Arm 4: placebo tablets + placebo drink The study uses a randomised double-blind, double-dummy design. Participants will consume two substances (drinks and tablets) but will not know which is placebo and which is active. The tablets are consumed, with the drink consumed immediately after, over a 10-15 minute period. Participants will be instructed to abstain from alcohol and drugs for 24 hours, and from cigarettes, caffeine, and eating for two hours before the session. At the beginning of the session, participants will screen for recent substance use and pregnancy, complete the demographics and drug history questionnaire, and receive a baseline blood (via venepuncture) and saliva test. Dexamfetamine/placebo pills will be administered by the study research nurse. Blood samples will be taken across a total of 2 time points to quantify plasma levels of substances. The stress and memory tests will occur at the study visit. The stress test is the Maastricht Acute Stress Test (MAST), which involves arm submersion in ice water alongside a social threat (maths task while evaluated and filmed). Memory will be tested via recall of the MAST event (to-be-remembered items counterbalanced across arms), the DRM word list task, and a face recognition task (employing the Chicago Face database). Memory and stress tests will occur approximately 30 minutes post substance administration. Salivary cortisol will be collected to quantify stress levels. These tasks will be completed by trained researchers. Participants will remain on site until it is safe for them to leave as per standard clinical protocols (e.g., >4 hours since dose, clinician review).
Sponsors
University of Sydney
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Educational / counselling / training
Masking
Blinded (masking used) (Subject, Caregiver, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
1) Self-reported previous experience with the substance of interest but not current regular use. Regular use is defined as taking amphetamines for non-medical purposes more than once a week. 2) Adequate cognition and English to consent and complete the study. This will be determined by the researcher who administers the phone screening.
Exclusion criteria
1) Current, clinically significant physical disease (e.g., cardiac, liver). The nurse or doctor associated with the study will make this determination based on an examination of the potential participant. 2) Severe psychiatric illness (i.e., schizophrenia, suicide risk). The nurse or doctor associated with the study will make this determination based on an examination of the potential participant. 3) Current substance use disorder other than nicotine. The nurse or doctor associated with the study will make this determination based on an examination of the potential participant and the diagnostic tools. 4) Previous hypersensitivity/adverse reaction to the studied drugs. We will evaluate this based on the potential participant’s self-report. 5) Current medication use that is a contraindication for the study drug or interferes with drug absorption. The nurse or doctor associated with the study will make this determination based on an examination of the potential participant. Stable antidepressant use for > one month will be permitted. 6) Oral-contraceptive use in females. We will evaluate this based on the potential participant’s self-report. 7) Current pregnancy/lactation. We will evaluate this based on the potential participant’s self-report in the first instance (phone screen) but also via pregnancy testing prior to study session commencement. 8) Women of child-bearing capacity who are not prepared to use (non-pharmacological) contraception during the study. We will evaluate this based on the potential participant’s self-report. 9) Participation in at least 1 session of the REMDAS-A study (See ANZCTR: ACTRN12624000645550) due to priming and familiarity with study activities.
Outcome results
None listed