Yeah, it was a time of horrors. People tend to forget that of the population of the world, that flu epidemic killed several times the number of the casualties of the preceding world war. It gets called the Spanish flu, but it is suspected to have come originally from Asia, and to have probably been one of the viral infections that jumped from pigs and/or poultry to humans, so we had no resistance.
And the PTSD was certainly a thing. I remember my dad's screaming nightmares. Very fortunately for his unit, he was a skilled bushman as well as a medic, so after they got cut off in jungle he managed to keep them alive for several months, and after they were finally taken, to keep them alive and as healthy as they could be in the prison camp because he knew what weeds and wildlife were safe to eat. He came out of that war with a slew of medals he didn't want, permanent scars both physical and mental, and a greatly lowered opinion of human nature. I think he deserved a day of honour once a year.