Selective serotonin reuptake inhibitors (SSRI) are the most commonly prescribed antidepressants. It has been suggested however that SSRI administration may affect response inhibition and contextual processing but the available evidence is minimal. Therefore, the purpose of this study was to identify the effect size of acute (within 24 hours) and chronic (28 days) administration of the highly selective SSRI, Citalopram, compared to placebo on response inhibition (measured by the Degraded Symbol Continuous Performance Task [DS-CPT]) and contextual processing (assessed using a Delayed Non-Matching to Sample Task [DNMS]) in healthy males (n=20) using a randomised double-blind design. We found no effect of Citalopram on participants' performance on the DS-CPT which suggests either that SSRIs do not affect response inhibition or that this measure is insensitive to any potential disinhibition effects of SSRI. Acute, but not chronic, Citalopram administration was associated with a measurable decrement in the DNMS suggestive of a negative impact of SSRI administration on contextual processing at least during treatment initiation. These findings provide a useful guide for designing future studies in clinical populations.
2009. Published by Elsevier SAS.