Therein is part of the problem with any kind of statistics that some say should be available. How many clients go for one or two appointments and stop because they decide it isn't for them? Do they count in the statistic? No real therapy even got started? How many stop therapy because of financial concerns? Do their statistics count if they left therapy without it coming to any sort of close? What is the length difference for clients with X type of situational issue as opposed to clients with Y type of more involved issued as opposed to clients with Z serious mental illness diagnoses such as schizophrenia as opposed to clients with some combination of the above that defy any sort of predictability because of the issue of variance with comorbid issues? What is the length difference for different modalities of therapy? What about clients with therapists who don't fit neatly into any particular modality? How any sort of reliable statistics could be the least bit useful to an individual I have no idea except in what is probably the rare circumstance of someone with a very clearly defined disorder in a very specific kind of therapy modality conducted to the letter and by the book. Most of us, quite frankly, don't fit into that neat, statistically traceable category.

It is going to take time for a therapist to have any sort of clear handle on what a client needs, how long it is going to take, what modalities might be best suited, how the client is going to respond to treatment along the way. That is individual. This is particularly a problem in therapy where clients often either do not really know what they want from their own therapy to start with and/or they are not completely open from the beginning and/or they are not completely honest from the beginning and/or other problems occur during the course of therapy that create additional fodder for assistance; none of these are unusual or even particularly wrong, but they highlight the problem of expecting a therapist to make prediction and give warnings to a client about themselves based on virtually no information to start with. No blanket statement could be remotely accurate to the individual or even really particularly helpful or predictive. Personally, I would run from a therapist who started making warnings and predictions early on about how long they thought it would take, what they thought my chances of success/failure were, etc.

Sure, they can have you read and sign a form about all the possible horrible things that might possibly be a problem for you in therapy. Have you ever had to sign one of those forms for a medical procedure? They are CYA documents about generally obscure possibilities that never apply to everybody and in fact apply in only rare instances. Personally, I've never backed out of a medical procedure based on informed consent and I've never had one of those rare scenarios actually happen. My sister did have one of those rare scenarios happen, but she would not have backed out of the treatment if you had put a gun to her head because the treatment was her only chance at life. Yes, people could choose to back out of therapy right then and there and I suppose that is what the OP is looking for? I don't know. Of course, the only danger of backing out of therapy due to informed consent, I suppose, is that a person continue to live their life in mental and emotional instability or pain or whatever it is that brought them in (but of course, continued self-harm or successful suicides could certainly be a tragic outcome of someone running from treatment based on such predictions . . . )

I am not saying any therapist should tell any client it will all be better and turn out roses -- not in the least. But these conversations have to happen over time in the context of the individual as the therapist gets to know the client and the client's needs more closely. It's not like antibiotic B is going to cure infection B; it's just not anywhere near that statistically predictable. How soon can a therapist have a better idea for an individual client? Again, that would vary with the client. The best a therapist could do might be very broad statements that would not be particularly individual at all. I prefer to be treated as the individual I am rather than be given some CYA statement early on that probably wouldn't apply to me anyway.