This study is investigating whether acute administration of citalopram is associated with a
decrease in stress reactivity in healthy volunteers, compared to placebo administration.
Using a parallel-group double-blind design, participants will be randomised to receive either
an acute dose of citalopram or placebo. All participants will have come in for a screening
visit. On the day of the research visit (following drug administration) participants will
have completed a number of widely used computer-based cognitive tasks measuring emotional
processing biases. They will then complete the Oxford Cognition Stress Task, a web-based
acute stress induction paradigm, which is designed to induce mild transient increases in
stress and arousal. Identifying early changes in stress reactivity following antidepressant
treatment will increase the investigator's knowledge of how antidepressants operate, and
provide putative targets to identify early response to antidepressants.