REMDAS-A2: Recollection of Event Memory following Drugs, Alcohol, and Stress

INTERVENTION: 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 se Xusing 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. Th CONDITION: Memory Impairment; ; Memory Impairment Mental Health ‐ Studies of normal psychology, cognitive function and behaviour PRIMARY OUTCOME: Face recognition memory (visual)[Recognition and confidence ratings of faces previously presented using the Chicago Face Database Approx 45 mins post substance ingestion] Recall memory under stress[Maastricht Acute Stressor Test Memory Task; Free recall assessment of items present in the room, characteristics of the researcher (clothing, key statements), tasks etc Approx 45 mins post substance ingestion] Recall memory[Deese Roediger McDermott Word list task: Recall of words presented Approx 45 mins post substance ingestion] 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. SECONDARY OUTCOME: Alcohol intoxication[Alcohol intoxication Visual Analogue Scale 6 time points: 45 mins post drug administration, 15 mins after that, 15 mins after that, Then at appro X4 hours post drug administration) and at discharge (appro X5 hours).] Amphetamine intoxication[Dexamphetamine intoxication Visual Analogue Scale 6 time points: 45 mins post drug administration, 15 mins after that, 15 mins after that, Then at appro X4 hours post drug administration) and at discharge (appro X5 hours).] Positive and Negative Affect Schedule (PANAS)[Questionnaire assessing positive and negative affect in response to study procedures Collected at baseline and appro X45 mins post stressor (MAST)] Recall memory[Deese Roediger McDermott Word list task: Recognition of words presented Appro X2 hours post substance ingestion] Salivary cortisol[Cortisol will be assessed via saliva Three time points within the session: baseline, 35 minutes post‐stressor, and 50 minutes post‐stressor.] Stress and pain responses to MAST: composite[‐ Maastricht Acute Stress Test ‐ Cold Pressor Task Questionnaire ‐ Maastricht Acute Stress Test ‐ Subjective Stress Response Questionnaire ‐ Stress ‐ Maastricht Acute Stress Test ‐ Subjective Stress Response Questionnaire ‐ Distress ‐ Maastricht Acute Stress Test ‐ Subjective Stress Response Questionnaire ‐ Pain Response Scale Appro X45 mins post stressor] Stress ratings[Scale of distress experienced during session 0‐10 (10 = highest stress) Assessed 6 times across session; 1 baseline, 1 appro X45 mins post MAST, 15 mins later, 15 mins later again, appro X3 hours later, and at discharge] Stress via salivary alpha amylase[Salivary alpha amylase Appro X2 mins post stressor]