"I don't like the word regression, which is the most common word used when an autistic person starts losing skills or appearing more outwardly autistic. I also don't like the terms setbacks and backsliding in this context. This is not because it isn't politically correct, but because it's both inaccurate and loaded with the potential for erroneous and damaging conclusions.
One reason I don't like these words is because they essentially mean growing backwards. I do not believe it is possible for a person to grow backwards. I have lost skills during two major periods of my life so far. I have never grown backwards. In some people, also, looking more stereotypically autistic can be a positive sign β a sign that they are no longer faking things, for example, and that they are learning how to do new things their way, a way that works better for them. This is not true for everyone, but I don't think the concept of growing backwards applies.
Another reason is the way people treat a person when they believe that person has grown backwards. There can be a tendency to view a person almost as if they have died, and been replaced by a new person. People say "I want the old you back," meaning they want their fantasy of what you would have been like if you had not changed in certain ways. This can also happen to people who have changed after a traumatic event, or after brain damage.
From the point of view of a person who has lost skills, this put a tremendous amount of pressure on me. Every time I did something that seemed to show a gaining of approved skills, it got called progress, and every time I even took a break, much less lost those skills again, it got called setbacks, backsliding, or regression. I started reacting with violence every time I heard one of those words, which I doubt is the effect people around me were looking for. It felt like people didn't care about who I was, only who I could have been, and were determined to make me into their vision of who I could have been.
It was also not pleasant to be talked about in front of me as if I had died and someone else had taken my place. I was perfectly capable of hearing this, and the implications β that I was undesirable and inferior to people's fantasy of who I could have been β came through loud and clear. It made me feel like an unwanted person who had mysteriously taken the place of a real, desirable person, or like I was being haunted by other people's fantasy-ghost of who they wished I was. The person after I lost these skills, and while I was losing these skills, was and is still undeniably me. I was aware of many things people thought I was not aware of, and being regarded by many as irrevocably damaged and inferior took its toll.
It is disrespectful to a person to expect them to measure up to the standards of a fantasy-ghost of who you wish them to be. It is possible to encourage a person to learn things and regain skills without making it sound like the person they are is inferior to the person they could have been. It can be especially important because internalizing the fantasy-ghost as a superior being can be a fast track to self-hatred and emotional or physical self-destruction. Respecting a person (or yourself) where that person is at, while possibly wanting to change some things, is much better for everyone involved than wishing that person were someone they are not. Losing skills can be scary. There's no reason to make it more scary by thinking of it as growing backwards or using emotionally provocative metaphors.
These words can cause problems for autistic people who have been faking normalcy for a long time. When people say "I want the old you back" or "You have regressed," it can sound to the person like "I liked the pretend-you better than the real you" or "To act like who you really are is to grow backwards, not forwards." This can devastate a person emotionally, and it can even shame them into expending an enormous amount of energy faking normalcy to the detriment of their health, their emotions, and their ability to deal with life. Since faking normalcy can kill through burnout or suicide, to refer to dropping a facade as regression or undesirable can have serious consequences. The same is true for people who use more stereotypically autistic ways of dealing with the world in order to make it easier to do other things, or people for whom learning to do something important to them can mean losing another skill somewhere else.
It is important to know that the growth of people is a complex process that cannot be reduced to a simple one-dimensional model of progress versus regression, growing backwards or forwards. Especially among autistic people, a person's normal developmental pattern can vary greatly. The consequences of many of the connotations of growing backwards are non-trivial both for people who have lost skills and for people who have dropped a facade or learned to utilize more useful autistic-style skills. Regression can be in the eye of the beholder, and personal growth or integrity is not necessarily the same as looking less autistic.
As for what terms are applicable, I think it's best to stick to straightforward descriptive terms that describe what seems to be really happening β loss of a skill, gaining of a new but unusual-looking skill, change in behavior, dropping of a facade (if you know that's what's happened), or anything else that seems like a true descriptor rather than something that draws too many conclusions. It's my belief that referring to becoming more autistic or to a lower functioning level draws as many false and broad conclusions as regression does."
Mel Baggs, On Regression, Autism Information Library: Help! I Seem to be Getting More Autistic!"