Medical device for delivering neuro-stimulation and neuromodulation for treating psychological and neuropsychological disorders, including, PTSD, trauma-related disorders, depression, anxiety, insomnia, epilepsy, migraines, ADHD, mild cognitive impairment, Alzheimer's, rheumatoid arthritis, autism spectrum, pain, and addiction; earbud-style medical device delivering neuro-stimulation to the transcutaneous vagal nerve for treating psychological and neuropsychological disorders, including, PTSD, trauma-related disorders, depression, anxiety, insomnia, epilepsy, migraines, ADHD, mild cognitive impairment, Alzheimer's, rheumatoid arthritis, autism spectrum, pain, and addiction; closed loop neurostimulation device for treating psychological and neuropsychological disorders, including, PTSD, trauma-related disorders, depression, anxiety, insomnia, epilepsy, migraines, ADHD, mild cognitive impairment, Alzheimer's, rheumatoid arthritis, autism spectrum, pain, and addiction.