A system and method for the biological diagnosis of Post-Traumatic Stress Disorder (PTSD) comprises an electronic device equipped with a built-in or attachable camera, built-in or attachable flash or controllable light source, and a software application. The software application includes a method that records and monitors the diameter of an individual's pupil prior to and after the application of light, using the camera and flash in communication with the electronic device. In another embodiment, the method includes the use of emotionally-charged visual stimuli to increase the accuracy of the diagnosis. In still another embodiment, a heart rate monitor in communication with the electronic device is used to monitor the individual's heart rate variability to further increase the accuracy of the diagnosis. In still another embodiment, the method also measures the auditory startle response. The method analyzes the data collected and determines the likelihood the individual suffers from PTSD.
