Not sure who is closed off to other theories, I'm just exploring this theory presently.
In transcribing the episode of Disappeared, please reference the following:
Rolfe Koecher: We knew he was struggling and like I say that's why we wanted him to come home.
Narrator: Deanne suspects that it is something worse than a jaunt to Las Vegas. She's afraid that loneliness and financial troubles have overwhelmed him.
Deanne Koecher: I thought life really got too tough for him, he's walked out into the desert, and was horrified by that but that's kind of where I went in my head first.
Detective: The family believes that it is a possibility that Steven has some sort of mental issue.
Narrator: His mother believes his mental instability could have been caused by depression or a blow to the head.
Deanne Koecher: Maybe he was going to walk away from the life the he knew so there was a mental disconnect and he was just going to a totally different life.
Deanne Koecher: That someone wanted to hurt him or kill him, that makes even less sense to me but that is where my head is now.
In some of the posts here on WS, statements have been made that the family didn't believe that SK had any mental health issues. But, the interviews of DK would say otherwise. If DK didn't believe that there was an emotional/mental health problem, then why would she make those comments?
If SK was doing very well emotionally and mentally, why would his mother's first thoughts about the reasons for SK's disappearance be that he had wandered off into the desert (implied suicide) because he was overwhelmed and/or had a mental disconnect and entered a new life?
And, what does DK mean by mental disconnect? Mental breakdown? Loss touch with reality? All euphemisms for psychosis...disconnected from reality. She seems comfortable entertaining the idea that he had a psychotic episode, maybe we should be too?
The detective references that the family believes that SK may have had some mental illness. The show's writer and by default the narrator also stated that DK
believes that SK's mental instability (meaning instability was present and acknowledged) was caused by depression or a blow to the head.
For those who think the head scar is a scar and not a cowlick, his mother believes his mental instability could have been caused by a blow to the head, one that perhaps she was aware of him incurring. On a side note, head injuries can cause depressive symptoms and here's a link, but it's not the only website out there that documents the causal relationship between head injuries and depression...Link:
www.braininjury.com/symptoms.html
It would seem that if someone was very happy, contented, showed no signs of being suicidal, that if they went missing would inferred suicide (walked off into the desert) be the first thought to come to mind?
Sounds like SK's family, more specifically his mother, have much more of a understanding and belief that mental illness is for the reason behind his disappearance.
Maybe revisiting mental illness isn't a bad idea based upon DK's statements. She's a pretty reliable source and knows SK better than any of us.