May have been mentioned here before, but read the book "One Second After". It's a fictional look at an EMP attack on the USA and its implications. The authors discuss this issue in some depth, specifically what will happen when people who need meds to stabilize their emotional problems run out of medicine. It is a chilling book, and I highly recommend you read it if you want to know what a particular type of SHTF situation (EMP attack) entails.