I think these are good insights Crayola writes about. I would not rule out mental illness, such as bipolar cycling.
But the thing is, we cycle too. In the sense that every time our kids look like they show surface changes, such as working, off drugs, taking medication, borderline cooperative, all of a sudden our despair turns to optimistic glee and we throw the confetti. I do.
In fact, I can do this even without any information at all. There was a 3-month lapse in communication with my son. and rather than have nightmares of doom and loss and degradation, I did the opposite. I had wide-awake dreams he had turned the corner, had met a girl, gotten married and a baby was on the way (oh how I have longed to be a grandmother.) All of this was a fantasy, my fantasy.
Not only do we get mesmerized by surface stuff (or even no information--in my case) I think our adult children do too. They think "easy peasy," "piece of cake, "I've got this." And when they are lured by their drug of choice they are not insulated by learning and wisdom achieved. (This is the reason for sponsors in 12-step groups.) They have characterological weaknesses or lack of will or whatever you want to call it. They are not self-aware.
This is what recovery really is--a characterological change that comes from consistent work and support, an actual re-working of the personality and understanding of life. Without that, our kids believe life is one thing when it is really quite another. Life is 
ing hard. Recovery is ing hard. It's work. Real consistent work.
So the cycling in helpless' son may be just foolishness in believing he has got this licked and he can do whatever he wants. Again.
Summing up, while there may be a cycling internal psychological process that is affecting helpless' son, it may also be hubris, laziness, or immaturity too. He may get bored. He may just want to do the easy thing. Or he may fall into wishful thinking (like I do.)
But the thing is this: I don't know how we as mothers recover from wanting to have hope.
