My Dead Friend Zoe,” starring Natalie Morales and Sonequa Martin-Green, confronts a dark reality of post-combat struggle with as much humor and playfulness as it does trauma and sorrow.

“My Dead Friend Zoe” is based on an idea that sounds like it wouldn’t work: It’s a buddy comedy about PTSD. Lean too far in one direction and the movie ends up being empty and flippant; veer too far in the other and it becomes dreary and heavy-handed.