Intranasal Insulin for Posttraumatic Stress Disorder

To evaluate if intranasal insulin is effective in reducing PTSD symptoms.

Inclusion Criteria: * Male or female, 21-65 years old * Current PTSD * Able to provide written informed consent Exclusion Criteria: * Unstable medical condition, clinically determined by a physician * Diabetes requiring insulin or oral hypoglycemic agents * Moderate-severe traumatic brain injury * Current psychotic disorder, bipolar disorder, cognitive disorder in the past 12 months * Current substance use disorders (except alcohol, tobacco, or cannabis) in the past 3 months * Changes in doses of psychotropic medications in the past 4 weeks * Initiation of individual therapy or counseling in the past 4 weeks * Imminent suicidal or homicidal risk * Contraindication to Insulin * History of claustrophobia * Presence of cardiac pacemaker or other electronic device or ferromagnetic metal foreign bodies in vulnerable positions as assessed by a standard pre-MRI safety screening questionnaire