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.
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
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.
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);
Parallel
Fluoxetine
DrugParticipants will be taking a 20mg fluoxetine capsule daily for 7 days.
Placebo
DrugParticipants will be taking a placebo capsule daily for 7 days.
Behavioural measure: Facial Expression Recognition Task (FERT)
Recognition of positive (happy, surprise) faces in the Facial Expression Recognition Task.
Self-report measure: the Need Threat Scale
Participant scores on the 20-item Need Threat Scale, administered after the Cyberball task (an ostracism paradism). The scale ssesses self-reported current satisfaction levels with belonging, self-esteem, meaningful existence, and control on 7-point scales ranging from 1 (do not agree) to 7 (agree), serving as a proxy of whether these needs are threatened.
Behavioural measure: Probabilistic Reversal Learning Task
Performance on a probabilistic reversal learning task, in which participants learn probabilistic reward contingencies associated with three stimulus images, and them must relearn when those contingencies are reversed.
Behavioural measure: Piggybank Task
Performance on a task measuring action vigour, where participants have to earn monetary rewards by pressing keys to "shake" coins from virtual piggy banks. Piggybanks vary in effort and reward, requiring ongoing adjustment.
Self-report measure: Perception of social rejection on the Verbal Interaction Social Threat (VIST) Task
In the Verbal Interaction Social Threat Task, participants are led to believe they will be engaging in an online interaction with two other study participants. Participants are shown a series of prompts and, for each one, choose one of four possible "icebreaker" sentences (for example, under the theme of sport: "I play a team sport such as football, rugby or netball" or "I play an individual sport like tennis or athletics"). After each choice, they receive responses that appear to be typed in real time by the two peers. In reality, these responses are pre-programmed and skewed toward negative feedback for most prompts (e.g., a peer might reply "I think team sports are more like a game than a real sport"). Following each exchange, participants rate how positively or negatively they perceived the interaction.
Physiological measure: Heart Rate Variability in response to social rejection
Heart rate variability measures across tasks inducing social rejection.
Physiological measure: Facial Expression in response to social rejection
Video recordings that identify facial expressions across tasks inducing social rejection.
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University of Oxford
Lead sponsor
Wellcome Trust
Collaborator
National Institute for Health Research, United Kingdom
Collaborator
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