Selective serotonin reuptake inhibitors (SSRIs) are thought to exert their therapeutic action through increased serotonergic neurotransmission and hippocampal neurogenesis. Both of these processes may also contribute to the disinhibiting effects of SSRIs currently considered to contribute to potential risk of suicide or self-harm.

This study examined the acute (3 hours) and chronic (28 days) effects of citalopram administration on response inhibition and contextual processing (a hippocampal related function). Twenty healthy male volunteers were randomised to either placebo or 20 mg of oral citalopram for 28 days in a double blind design. Response inhibition was measured with the degraded symbol continuous performance test (DS-CPT) and contextual processing with a visual delayed non-matched to sample task (DNMS).

Citalopram treatment did not produce measurable changes to reaction time, hit rate and false alarms in the DS-CPT at any time point. The citalopram treated group underperformed in the DNMTS after acute treatment and this decrement appeared to persist at 28 days.

Our results suggest that SSRI treatment may lead to small but measurable decrements in contextual processing, which require further confirmation, and evaluation in clinical populations.