Results you retrieve from Google searches are found on the surface web where information is not evaluated. Results from library databases are found on the deep web where information is evaluated. With Google searches you're finding only the tip of the iceberg.
Library databases help you find information that has been vetted and checked for accuracy. Also, library databases help you find articles that you can't find via Google.
PTSDpubs is a bibliographic database produced at the headquarters of the National Center for Post-Traumatic Stress Disorder and is sponsored by the U.S. Department of Veterans Affairs. It includes citations to literature on post-traumatic stress disorder (PTSD) and other mental-health sequelae of traumatic events, without disciplinary, linguistic, or geographical limitations, while offering both current and retrospective coverage.