Title: ERG as a potential biomarker of SSRI-responsive PTSD: A pilot study

Posttraumatic stress disorder (PTSD) affects many individuals who experience a traumatic event. Previous studies suggest that there is a connection between the brain and the retina, and that the electroretinogram (ERG) may be a valuable biomarker to tell us more about signals in the brain that are related to mental health disorders like PTSD. The goal of this observational study is to examine the ERG waveform in veterans with PTSD before and after a single dose of the selective serotonin reuptake inhibitor (SSRI), sertraline. Sertraline is one of two FDA-approved medications for the treatment of PTSD. The main questions this pilot study aims to answer are:

1. How does sertraline, an SSRI, influence the ERG waveform in veterans with PTSD?
2. Is there a significant correlation between baseline ERG signals and the change in ERG following SSRI treatment?

Participants will be asked to:

• Undergo ERG recordings before and after a single dose of sertraline.
• Provide relevant clinical information related to PTSD symptoms and treatment history.

Following the initial study visits, participants will enter an optional open label phase of the study in which qualifying participants who initiate antidepressant treatment through routine clinical care will be invited back for a follow-up ERG recording.

In this study, individuals will undergo an assessment that includes taking a history of their previous exposure to traumatic events, an assessment of current mental health symptoms including those associated with PTSD, and an assessment of physiologic measures, including ERG as well as vital sign measurements, blood draw, and saliva sampling. Participants will be given a single dose of sertraline (50mg), and a repeat ERG will be administered. An optional open label phase of the study will follow, in which participants who undergo treatment with an antidepressant will be invited back for a follow-up assessment with repeat ERG.

Inclusion Criteria:

• Veteran of the U.S. Armed Forces
• Current diagnosis of PTSD

Exclusion Criteria:

• Known diagnosis of a primary psychotic or major neurocognitive disorder
• Significant bilateral visual loss
• History of acute angle closure glaucoma
• Known inherited retinal disease
• Previous ERG deficits
• Known photosensitive epilepsy
• Known current pregnancy or lactation
• Allergy or previous adverse reaction to sertraline or SSRI
• Allergy to Sensor Strip gel
• Hepatic failure
• Damage to orbit structure or open lesion in soft tissue surrounding the eye
• Any use in the time period of at least 6 half-lives prior to baseline of sertraline or other drugs acting on serotonin and/or unwillingness to avoid these medications for the duration of the study.