Age regression is when an individual psychologically returns to a mental state that is younger than they are. The age a regressor goes back to can differ from a few years younger to complete infancy.
The regression can be voluntary or involuntary. When it’s voluntarily, it’s usually used as a way for the regressor to relieve stress, regulate emotions, and/or deal with past traumas, such as in age regression therapy, by returning to a safer state of mind.
On the flip side, when agere (age regression) is involuntary, the mental headspace that the regressor experiences can vary from fun to traumatic, and usually these episodes are a sign of a mental health condition such as schizophrenia, post-traumatic stress disorder (PTSD), or borderline personality disorder, along with a list of others.