Citalopram and Stress Reactivity

Overview

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.

In the Oxford Cognition Stress Task (OCST), participants are presented with a series of mental arithmetic, verbal (anagrams) and visuospatial (visual search) challenges on a computer screen. There is a time limit for completing each challenge, which is displayed on the screen as a time bar. To induce a high failure rate, the timing and difficulty of the challenges is automatically varied to ensure participants are correctly complete only 20-40% of the challenges within the time, and some of the verbal challenges (anagrams) are impossible to solve. Participants are given feedback on their performance on the screen which indicates that they are performing badly. Heart rate will be measured continuously during the OCST, and during pre- and post- task periods. Baseline and post-OCST measures of blood pressure and samples of saliva (for cortisol analysis) will be taken. Participants will also complete Visual Analogue Scales pre- and post-OCST to give a subjective measure of stress and mood. Participants will not be told the extent to which becoming stressed (and finding the task difficult) is intended. At the end of the test session, participants will be fully debriefed as to the nature of the OCST.