Check out our "Finding Statistics" guide for more information on finding statistics from multiple areas of study:
Combine keywords for a more complex search. Use the word AND to combine key words together and OR to search for one term or the other.
If you want to research historical documents on PTSD, try using the term "shell shock." While no longer used in medical or military discourse, shell shock was used to describe the PTSD like trauma World War I veterans experienced.