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Fluoxetine on Emotional Experience (FLEX) Study

The Effect of Fluoxetine Treatment on Anger Processing in Healthy Young People

Status
Recruiting
Phases
Unknown
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT07424781
Acronym
FLEX
Enrollment
80
Registered
2026-02-20
Start date
2025-10-01
Completion date
2026-12-31
Last updated
2026-02-20

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Depression, Depression - Major Depressive Disorder, Irritability

Keywords

depression, young people, fluoxetine, irritability, anger

Brief summary

The goal of this clinical medicine study is to investigate how does antidepressant fluoxetine modulate anger processing in healthy young people . The main questions it aims is to answer are: 1. How does fluoxetine affect responses to anger-related stimuli such as words, faces, and autobiographical recall? 2. How does fluoxetine influence responses during frustration induction in frustrative non-reward and threat paradigms? 3. Does the effect manifest in physiological markers, including heart rate variability and facial expressions? Researchers will compare fluoxetine to a placebo to see if drug fluoxetine affects anger processing. Participants will: Take 20mg fluoxetine or a placebo every day for 7 days. Visit the university site for questionnaire and tasks assessments. Heart rate variability and facial expressions will be recorded in some of the tasks.

Interventions

DRUGFluoxetine

Participants will receive 20mg of fluoxetine daily for 7 days. Tablets encapsulated to aid blinding.

DRUGPlacebo

Participants will receive one dose placebo (sucrose) daily for 7 days. Tablets encapsulated to aid blinding.

Sponsors

University of Oxford
Lead SponsorOTHER
Wellcome Trust
CollaboratorOTHER
Oxford Health Biomedical Research Centre (OH BRC) support scheme
CollaboratorUNKNOWN

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)

Intervention model description

Participants will be assigned to receive either fluoxetine or placebo. Fluoxetine is not being administered for treatment purposes, the purpose is to understand the mechanisms underpinning its effects.

Eligibility

Sex/Gender
ALL
Age
18 Years to 24 Years
Healthy volunteers
Yes

Inclusion criteria

* Be aged 18-24 years (inclusive) * Be resident in the UK for the duration of the study * Have normal or corrected to normal vision * Participant is willing and able to give informed consent for participation in the research * Sufficiently fluent English to understand and complete the study

Exclusion criteria

The participant may not enter the study if ANY of the following apply: Psychiatric History: * Current or past diagnosis of any psychiatric disorder, as determined by the Structured Clinical Interview for the DSM-5 (SCID-5) and self-report. This includes, but is not limited to, depression, anxiety disorders, alcohol or drug dependency, personality disorders, suicidal ideation, and other psychiatric conditions; * First degree relative with a diagnosis of mania; Lifestyle: * Heavy smoker or vaper (\> 10 cigarettes per day, or \>2 mL e-liquid, or \>15mg/day from a nicotine patch); * Heavy use of caffeine (drink \> 4 of 250ml cups/cans of coffee or energy drinks per day); * Heavy drinker (drink \>14 standard alcoholic drinks per week); * Current or recent use (in the last 3 months) of any psychoactive substance according to self-report and a urine drug test screening for recent use of 10 common recreational substances; Physical Health: * Severely underweight or overweight in a manner that renders them unsuitable for the study in the opinion of the study medical advisor; * Known contraindication to fluoxetine, such as hypersensitivity to fluoxetine or any component in its formulation; * Pregnancy, as determined by a urine pregnancy test or plans to become pregnant within the next 3 months; * Breastfeeding; * Not able to consume gelatine; Medical History: * Past or ongoing health issue which, in the opinion of the study medical advisor, may interfere with the safety of the participant or the scientific integrity of the study, including but not limited to: seizures or epilepsy, heart rhythm problem, renal disease, hepatic disease, glaucoma, diabetes, bleeding disorders or clotting conditions (e.g., haemophilia, thrombocytopenia); * Diagnosis of a significant neurological condition (e.g., epilepsy, multiple sclerosis, traumatic brain injury). * Diagnosis of a neurodevelopmental condition, such as autism spectrum disorder (ASD) or attention-deficit/hyperactivity disorder (ADHD); * Current or recent use of medication that might interfere or interact with the effects of fluoxetine, in the opinion of the study medical advisor, including but not limited to: monoamine oxidase inhibitors (MAOIs), medications affecting serotonin levels (e.g., tramadol, triptans, St. John's Wort), anticoagulants or blood thinners (e.g., warfarin), anti-inflammatory medications (e.g., aspirin, ibuprofen), or medications known to affect heart rhythm; Prior Study Participation: * Participation in any other psychological or medical experiment involving taking any kind of drug/medication/vaccine, within the last 3 months; * Participation in any other study involving the current or similar tasks, within the last 6 months; Others •Any other significant finding which may arise during the screening process and which, in the opinion of the Principal Investigator/medical advisor, may influence the scientific integrity of the study, or the participant's ability to participate in the study.

Design outcomes

Primary

MeasureTime frameDescription
Behavioral Measure: Facial Expression Recognition Task (FERT)On the last day of the 7-day treatmentRecognition of angry faces in the Facial Expression Recognition Task

Secondary

MeasureTime frameDescription
Behavioural Measure: The Affordances TaskOn the last day of the 7-day treatmentPerformance on an affordances task in which participants have to decide to fight or escape under threatening situations with different environmental affordance conditions.
Behavioural Measure: Emotional Categorization Task (ECAT)On the last day of the 7-day treatment.Performance on recognising and memorising anger related words in the Emotional Categorization Task (ECAT)
Performance on Carnival TaskOn the last day of the 7-day treatment.Performance on an anger induction task in which the study's rigged design creates frustrating non-reward responses.
Subjective Measure: Rest TaskOn the last day of the 7-day treatment.Participants' rating of anger-related emotions during a resting task.
Subjective Measure: Anger Memory Recall TaskOn the last day of the 7-day treatment.Participants' ratings of anger-related emotions and bodily sensations during a task that involves guided imagery of a past personal experience.
Physiological Measure: Heart Rate VariabilityOn the last day of the 7-day treatment.Heart rate variability measures across a battery of anger-induction tasks.
Physiological Measure: Facial ExpressionOn the last day of the 7-day treatment.Video recordings that identify facial expressions across a battery of anger-induction tasks.
Behavioural measure: Emotional Recognition Memory Task (EMEM)On the last day of the 7-day treatment.Description: Performance on recognising and memorising anger related words in the Emotional Recognition Memory Task (EMEM).

Countries

United Kingdom

Contacts

CONTACTCatherine Harmer, PhD
catherine.harmer@psych.ox.ac.uk+441865 618326
CONTACTYe Wo, MSc
ye.wo@psych.ox.ac.uk+447564300004

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 21, 2026