This side effect is still being researched and is controversial currently. This is because studies have conflicting conclusions, with some resulting in a decrease in cognitive function as a result of long-term use of SSRIs (and other antidepressants), while some maintain increased functioning reported as a result.

Cognitive impairment refers to impaired memory, concentration, attention, motivation, and/or affective response to external stimuli (Bolling & Kohlenberg, 2004). SSRIs specifically are hypothesized to be associated with mild and episodic memory impairments.