This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
Post-traumatic growth was a theory for explaining how positive psychological change could occur in an individual after they experienced certain life events which were traumatic to them. Dying, time travel, and living for a year alone in a new future were some of the life events which might trigger this growth. The event or events would inspire the individual into evolving and living life in a different way.
In 3189, Doctor Hugh Culber identified Commander Michael as someone who was still in this process. Furthermore, he believed Adira would be starting her own process when she regained her memories. (DIS: "Forget Me Not")