There are a lot of reasons to worry about Dark Phoenix considering the track record of the X-Men movies but it sounds like at least one cast member put in the time to do some research. The idea of the dark phoenix is Jean Grey being taken over by something much more powerful than her. There are a couple parallels that could be drawn there as far as mental illness goes.
Sophie Turner spoke to Screen Rant about the research she did going into this [possibly final] round with this character.
As soon as Simon [Kinberg] kind of told me what the movie was about we just started straight away sharing ideas, sharing materials. Simon gave me a big, big book on schizophrenia. I actually found this thing online, on YouTube. And it was just kind of repeating, repeating, repeating, what it sounds like being a schizophrenic. So I used to walk around town with all these voices in my head. Kind of feel it out. And see what it felt like. We also explored Multiple Personality Disorder as well. And what that feels like to kind of wake up and not know what you did, What happened and that shear panic and how that affects you. Jean is just… this movie… She’s so, so, layered. She’s so complex in this movie. I really don’t think that I’ve done more research for a role than for this one and I loved every minute of it.
There is a sensitivity issue if they try to draw a direct parallel but subtext is always a good thing. The X-Men movies have always been about subtext, it’s built into the fiber of the series, so adding some more in this context is not a bad idea. Now we just have to see if the execution works.
Summary: Jean Grey begins to develop incredible powers that corrupt and turn it into a Dark Phoenix. Now the X-Men will have to decide if the life of a team member is worth more than all the people living in the world.
Dark Phoenix, directed by Simon Kinberg, stars James McAvoy, Michael Fassbender, Sophie Turner, Jennifer Lawrence, and Nicholas Hoult. It will be released on June 7, 2019.