¹Mood and Anxiety Disorders Program, National Institute of Mental Health, NIH, Bethesda, MD, USA

Correspondence: Dr C Grillon, Mood and Anxiety Disorders Program, National Institute of Mental Health, NIH, 15K North Drive, Bldg 15K, Room 113, MSC 2670, Bethesda, MD 20892-2670, USA. Tel: +1 301 594 2894; Fax: +1 301 594 9959; E-mail: Christian.grillon@nih.gov

Received 22 May 2006; Revised 13 July 2006; Accepted 26 July 2006; Published online 13 September 2006.

Abstract

Serotonin reuptake inhibitors may increase symptoms of anxiety immediately following treatment initiation. The present study examined whether acute citalopram increased fear-potentiated startle to predictable and/or unpredictable shocks in healthy subjects. Eighteen healthy subjects each received two treatments, placebo and 20 mg citalopram in a crossover design. Participants were exposed to three conditions including one in which predictable aversive shocks were signaled by a cue, a second in which unpredictable shocks were anticipated, and a third in which no shocks were administered. Changes in aversive states were investigated using acoustic startle stimuli. Citalopram did not affect baseline startle. However, the phasic startle potentiation to the threat cue in the predictable condition was robustly increased by acute citalopram. The sustained startle potentiation in the unpredictable conditions was also increased by citalopram, but only when the drug was given during the first session. These results indicate that a single dose of citalopram is not anxiogenic in itself, but can exacerbate the expression of fear and anxiety.