Fluoxetine and Understanding Social Experiences
FUSE
Investigating the Effects of Fluoxetine on Reinforcement Learning and Social Cognition in Healthy Young People
1 other identifier
interventional
80
1 country
1
Brief Summary
Adolescence is a critical developmental period marked by significant social, cognitive, and emotional changes. Unfortunately, it is also a time when the risk of depression and anxiety rises dramatically. Early, effective treatment is essential to mitigate long-term impacts on relationships, education, and life satisfaction. While psychological therapies are recommended as first-line treatment for mild to moderate depression in young people, antidepressant use (particularly SSRIs such as Prozac) has risen sharply, especially among girls aged 15-17. Despite their widespread use, there is limited research on how SSRIs address adolescent depression, leaving clinicians with little evidence to guide treatment decisions. The Fluoxetine and Understanding Social Experiences (FUSE) study aims to shed light on how Prozac (medically known as fluoxetine) influences decision-making in healthy young people in four key areas that are known to be affected by depression: emotional processing (e.g., facial expression recognition), social function (e.g., sensitivity to peer rejection), reward processing (e.g., how people learn from rewards and punishments), and motivation (e.g., how people make decisions about whether a certain outcome or reward is worth the effort to obtain). Some of the tests employed in the study use facial expression and heart-rate recording as aditional measures. We are aiming to recruit and test 80 young people between the ages of 18 and 24. When included in the study, participants are randomly assigned to receive either a weeklong treatment with fluoxetine, or a placebo (a pill with no active ingredients). The study follows a double-blind design, which means that neither the researchers nor the participants are aware of the treatment received so as to not influence the results. We belive that fluoxetine will have beneficial effects on social decision-making in young people, which might manifest as increased accuracy labelling positive facial expressions, less sensitivity to negative feedback, lower self-reported negative mood in response to social exclusion and reduced heart rate/negative facial expressivity in response to unpleasant social experiences. The FUSE study aims to deepen our understanding of how antidepressants affect decision-making in young people, at a time when antidepressant prescriptions have risen but research is scarce. By identifying the exact domains of functioning which are affected by antidepressant use in this age group, this research will help inform which young people are likely to benefit most from drug treatment. The project results will be published in peer-reviewed journals and presented at academic conferences. We are also working with a group of young advisors who will help us decide how to best share our results with others in their age group. A brief summary of the study findings will also be provided to participants who would like to receive it. All research data, excluding information that could identify participants, will be stored safely for at least 10 years after final publication or public release.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P50-P75 for not_applicable
Started Mar 2026
1 active site
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
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Study Timeline
Key milestones and dates
Study Start
First participant enrolled
March 1, 2026
CompletedFirst Submitted
Initial submission to the registry
March 2, 2026
CompletedFirst Posted
Study publicly available on registry
March 6, 2026
CompletedPrimary Completion
Last participant's last visit for primary outcome
July 20, 2027
ExpectedStudy Completion
Last participant's last visit for all outcomes
July 22, 2027
March 6, 2026
March 1, 2026
1.4 years
March 2, 2026
March 2, 2026
Conditions
Keywords
Outcome Measures
Primary Outcomes (1)
Behavioural measure: Facial Expression Recognition Task (FERT)
Recognition of positive (happy, surprise) faces in the Facial Expression Recognition Task.
On the last day of the 7-day treatment
Secondary Outcomes (5)
Self-report measure: the Need Threat Scale
On the last day of the 7-day treatment
Behavioural measure: Probabilistic Reversal Learning Task
On the last day of the 7-day treatment
Behavioural measure: Piggybank Task
On the last day of the 7-day treatment
Self-report measure: Perception of social rejection on the Verbal Interaction Social Threat (VIST) Task
On the last day of the 7-day treatment
Behavioural measure: Proportion of anger-related solutions found on the Word Completion Task
On the last day of the 7-day treatment
Other Outcomes (2)
Physiological measure: Heart Rate Variability in response to social rejection
On the last day of the 7-day treatment
Physiological measure: Facial Expression in response to social rejection
On the last day of the 7-day treatment
Study Arms (2)
Fluoxetine
EXPERIMENTALPlacebo
PLACEBO COMPARATORInterventions
Eligibility Criteria
You may qualify if:
- 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
You may not qualify if:
- Psychiatric History:
- Current or past diagnosis of any psychiatric disorder, as determined by the 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 alcohol 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.
- Unable or unwilling to consume gelatine (study capsules will be gelatine-based).
- 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.
- Medical History:
- +8 more criteria
Contact the study team to confirm eligibility.
Sponsors & Collaborators
- University of Oxfordlead
- Wellcome Trustcollaborator
- National Institute for Health Research, United Kingdomcollaborator
Study Sites (1)
University of Oxford Department of Psychiatry
Oxford, OX3 7JX, United Kingdom
Related Publications (1)
Murphy SE, Capitao LP, Giles SLC, Cowen PJ, Stringaris A, Harmer CJ. The knowns and unknowns of SSRI treatment in young people with depression and anxiety: efficacy, predictors, and mechanisms of action. Lancet Psychiatry. 2021 Sep;8(9):824-835. doi: 10.1016/S2215-0366(21)00154-1.
PMID: 34419187BACKGROUND
MeSH Terms
Conditions
Interventions
Condition Hierarchy (Ancestors)
Intervention Hierarchy (Ancestors)
Central Study Contacts
Study Design
- Study Type
- interventional
- Phase
- not applicable
- Allocation
- RANDOMIZED
- Masking
- TRIPLE
- Who Masked
- PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
- Purpose
- BASIC SCIENCE
- Intervention Model
- PARALLEL
- Sponsor Type
- OTHER
- Responsible Party
- PRINCIPAL INVESTIGATOR
- PI Title
- Professor of Cognitive Neuroscience
Study Record Dates
First Submitted
March 2, 2026
First Posted
March 6, 2026
Study Start
March 1, 2026
Primary Completion (Estimated)
July 20, 2027
Study Completion (Estimated)
July 22, 2027
Last Updated
March 6, 2026
Record last verified: 2026-03
Data Sharing
- IPD Sharing
- Will share
- Shared Documents
- STUDY PROTOCOL, SAP, ANALYTIC CODE
- Time Frame
- Data will be available within 6 months of data collection completion (end 2027).
- Access Criteria
- Fully de-identified individual participant data (IPD) and relevant supporting documentation may be shared with academic researchers for scientific research purposes. Access will be limited to researchers affiliated with recognised academic or research institutions, including those outside of the UK and EU. Approved researchers will be granted access only to fully de-identified IPD and relevant supporting materials. Data will be shared via secure transfer methods or through a controlled-access data repository.
Data which has been fully de-identified and relevant supporting materials (e.g., study protocol, data dictionary, and analysis documentation) may be shared with other academic organisations in the future, including those outside of the UK and the EU. Participants will be informed of this and specific consent for this will be obtained.