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Abstract

Background:
Selective serotonin reuptake inhibitors (SSRIs) are used for the treatment of several conditions including anxiety disorders, but the basic neurobiology of serotonin function remains unclear. The amygdala and prefrontal cortex are strongly innervated by serotonergic projections and have been suggested to play an important role in anxiety expression. However, serotonergic function in behaviour and SSRI-mediated neurobiological changes remain incompletely understood.

Aims:
To investigate the neural correlates of subchronic antidepressant administration.

Methods:
We investigated whether the 2- to 3-week administration of a highly selective SSRI (escitalopram) would alter brain activation on a task robustly shown to recruit the bilateral amygdala and frontal cortices in a large healthy volunteer sample. Participants performed the task during a functional magnetic resonance imaging acquisition before ( n = 96) and after subchronic escitalopram ( n = 46, days of administration mean (SD) = 15.7 (2.70)) or placebo ( n = 40 days of administration mean (SD) = 16.2 (2.90)) self-administration.

Results:
Compared to placebo, we found an elevation in right amygdala activation to the task after escitalopram administration without significant changes in mood. This effect was not seen in the left amygdala, the dorsomedial region of interest, the subgenual anterior cingulate cortex or the right fusiform area. There were no significant changes in connectivity between the dorsomedial cortex and amygdala or the subgenual anterior cingulate cortex after escitalopram administration.

Conclusions:
To date, this most highly powered study of subchronic SSRI administration indicates that, contrary to effects often seen in patients with anxiety disorders, subchronic SSRI treatment may increase amygdala activation in healthy controls. This finding highlights important gaps in our understanding of the functional role of serotonin.

Publication Type:	Article
Additional Information:	This article is distributed under the terms of the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/en-us/nam/open-access-at-sage). © The Author(s) 2024.
Publisher Keywords:	Functional magnetic resonance imaging, emotion, antidepressants, escitalopram, anxiety
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Departments:	School of Health & Psychological Sciences School of Health & Psychological Sciences > Psychology
SWORD Depositor:	Symplectic Administrator

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