Brain Activity Patterns May Forecast Sexual Side Effects of Antidepressants

Depression often leads to various symptoms, including sexual difficulties that affect 40 to 60 percent of people with major depressive disorder. While treatment can improve mood, the medications themselves often create new challenges, particularly sexual side effects.

Selective serotonin reuptake inhibitors (SSRIs), the most frequently prescribed antidepressants, increase serotonin levels in the brain to alleviate depressive symptoms. However, 40 to 70 percent of SSRIs users report adverse sexual effects, including reduced sexual desire and difficulty achieving orgasm, which can significantly impair their quality of life, often leading patients to discontinue medication.

The study, led by Gudrun Dilja Ketilsdottir and Kristian H. Reveles Jensen from Copenhagen University Hospital and the University of Copenhagen, aimed to develop a method to predict patients' susceptibility to these side effects.

Researchers focused on a biological marker called loudness dependence of auditory evoked potentials, which is measured through electroencephalography (EEG). This technique tracks how the brain responds to sounds at varying volumes, with higher responses indicating lower serotonin activity.

To investigate, the team analyzed data from 90 unmedicated patients diagnosed with major depressive disorder, aged 18 to 57 years, with about three-quarters being women. Prior to any treatment, each participant underwent EEG recordings while listening to tones at five volume levels, and baseline sexual function was evaluated through questionnaires.

Eighty-six participants subsequently began an eight-week treatment with the SSRI escitalopram. The clinicians monitored their depression symptoms and any emergence of side effects. If there was inadequate response or intolerable side effects by week four, they were offered a switch to duloxetine, with seven patients making this change.

At the end of the treatment period, researchers correlated the initial EEG measurements with reported side effects. They found a significant connection between baseline brain activity and sexual difficulties, specifically noting that a weaker auditory response predicted higher rates of orgasmic dysfunction with 87 percent accuracy. The study also identified a weak correlation between the brain pattern and decreased sexual desire, but not with erectile dysfunction in male participants.

When blood testosterone levels were included in predictive models, there was no notable change in accuracy; the auditory brain response alone provided sufficient predictive power. Additionally, the brain response did not correlate with sexual dysfunction stemming from depression itself, indicating its specific link to SSRIs.

The researchers speculate that the brain marker captures the neurological pathways altered by SSRIs, given that orgasm relies heavily on certain serotonin receptors, whereas sexual desire involves a broader range of brain chemicals.

The study employed an open-label design, meaning both patients and clinicians were aware of the prescribed medication, which may have influenced reported changes in sexual function. Additionally, the average age of participants was 27.5 years, potentially limiting the broader applicability of findings to older adults. Since some participants switched medications during the trial, researchers performed a secondary analysis with only escitalopram users, yielding consistent results.

Moving forward, the research team aims to validate this biological marker in more diverse clinical populations. If successful, the auditory brain response could serve as a routine screening tool, allowing doctors to identify patients at high risk of sexual side effects and adjust prescriptions accordingly. The study was co-authored by Gudrun Dilja Ketilsdottir, Cheng-Teng Ip, Vibe G. Frokjaer, Annamaria Giraldi, Martin Balslev Jørgensen, and Kristian H. Reveles Jensen.