There is no substitute for face to face. Sure, I feel I communicate better in writing for a number of reason. I can collect my thoughts ahead of time. My thoughts flow better when I'm writing them down because the mere process of writing forces my brain into logical progressive thinking instead of the jumble that comes across with my speech. BUT there is a serious lack of the therapist's ability to OBSERVE first hand any shortcomings. Many shortcomings won't be apparent without long term exposure to each other.
For example, my current Primary Care doctor doesn't think I have autism at all because she only sees me in that setting for brief periods every few months. She doesn't see me when I'm not functioning well because I cancel on bad days. Why bother going if I can't communicate well that day?
On the other hand, if you're a stone when in a small cubicle with someone you don't know very well, and become nonverbal, skyping or messaging might help break the ice until you become comfortable.
The bottom line is though, you will never get the full benefit of your therapy if you don't meet face to face at all, so that should always be part of the goal along with using other methods.
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I'm not likely to be around much longer. As before when I first signed up here years ago, I'm finding that after a long hiatus, and after only a few days back on here, I'm spending way too much time here again already. So I'm requesting my account be locked, banned or whatever. It's just time. Until then, well, I dunno...