The goal of this study is to test whether active duty firefighters find it possible and suitable to do cranial electrotherapy stimulation (CES) at home, and test whether CES influences measures of depression and posttraumatic stress. The main questions it aims to answer are:

• is CES feasible and acceptable in a population of firefighters, and
• does CES changes feelings of depression, anxiety, and fatigue in firefighters.

Participants will

• complete four weeks of CES at home, and
• complete daily assessments of affect and fatigue, and
• complete self-reported symptoms of depression and posttraumatic stress before and after four weeks of CES at home Participants maybe asked to
• complete an MRI scan before and after four weeks of CES at, and
• wear a device to measure their heart rate and sleep quality.

Despite an urgent need for interventions that can prevent the development of posttraumatic stress disorder (PTSD) in firefighter first responders who, due to the nature of their occupation, are at ultrahigh risk for PTSD and its profound consequences, current preventative approaches suffer from low rates of efficacy or difficulties with implementation. Cranial electrotherapy stimulation (CES), a noninvasive brain stimulation technique that is FDA approved for treatment of anxiety, insomnia, and depression, offers substantial promise as a proactive preventative intervention for PTSD because of its hypothesized ability to reestablish homeostasis, a process that becomes dysregulated in individuals who develop PTSD. The proposed study is an administrative supplement that combines the unique strengths and knowledge of a complimentary team of scientists from two distinct Centers of Biomedical Research Excellence to test whether four weeks of CES is feasible and acceptable in firefighters as well as obtain early signal of CES efficacy to change subjective and objective indices of homeostatic functioning to allow a long-term collaboration with the ultimate goal to develop a safe, effective, and easily deployable intervention to prevent PTSD in first responders.

Inclusion Criteria:

• Active duty firefighter in Rhode Island, USA;
• Age between 18 and 56 years old;
• Be in good medical health or, if having chronic medical conditions, these conditions needed to be stable;
• Ability to speak, read, write, and understand English sufficiently well to complete study procedures and provide informed consent.

Exclusion Criteria:

• MRI and CES-related contraindications, e.g., implanted metallic device or substances including pacemakers, cochlear implant, metallic tattoos, claustrophobia, pregnancy or planning to become pregnant during the study duration and nursing;
• Neurological conditions such as brain neoplasm, cerebrovascular events, epilepsy or history of seizures, dementia, and neurodegenerative disorders, or had previously received brain surgery;
• Report presence of suicidal ideation on QuickSCID-5 or has attempted suicide one or more times within the past twelve months;
• Exhibiting a psychiatric condition that would require inpatient or partial psychiatric hospitalization;
• Current moderate or severe alcohol or other substance abuse (excluding nicotine);
• Major or unstable medical illness requiring further investigation or treatment.

Weekly during the one month of at home cranial electrotherapy stimulation