Well, everything about how the brain works (and dysfunctions) is indeed biochemical and biophysical processes. Feelings and behaviors are also associated with these. The way therapy can have effects is also via influencing those processes, it is not mystical at all, just unpredictable.

Addiction to therapy is something I have experienced quite strongly, in the end that's what kept me going, the pleasure factor. It also became a distraction from important other things in my life that I did not deal with properly. I am very certain of this because I had addiction problems before (in fact, the main thing I went to therapy for was also related to my addictions) and getting hooked on therapy felt very similar, including the cravings between sessions or after I ended therapy, relapses (reconnecting with the T), etc. I actually often think that when people talk about attachment to the T here on PC, especially continuing to go to a bad T, it is often a form of addiction. The whole process of therapy is very appropriate to elicit that kind of conditioning and habit formation: it has all the elements such as acute rewarding effect, reinforcement, environmental conditioning, repetitions. And I do believe that people who have a tendency to develop obsessions and addictions (like myself) are more likely to get hooked on therapy in a similar way and then it can be hard to stop even if the effects are negative.

I like this article, which was written by a PC member:
Therapy Consumer Guide - Can Therapy Become an Addiction?