It is not unlikely that the rigors of study, practice, etc. found in chanoyu (or perhaps other performative activities that require repetitive skills development handling tools or other objects, maybe even writing numbers or letters) can be attractive to a person who has a tendency to this type of behavior for whatever reason.
On the surface, nothing much happens in the practice of chado, but so much could be lurking behind a simple movement or decision (which scroll to hang, etc.) Likewise, there is an article in the LA. Times about how yoga has been found to be extremely valuable for veterans in the armed service who are suffering from PTSD or severe physical injury and are frequently in great pain.
When there is an attack on the senses, one might just "fight back" or "calm out" by retreating into an activity that is more in the person's arsenal of self-controlled behaviors. Maybe this is why playing scales on a musical instrument can actually become pleasurable, if not simply automatic, without emotional reaction.
Is it by accident that these two activities, which can become the objects of obsession by practitioners themselves, are effective? What is it about the view of life does the "Eastern" perspective that becomes therapeutically effective for the agitated "Western" mind? I believe It is not by chance that the two hemispheres of our globe are seeking to reconcile their lifestyles by engaging in activities of the other.
Hopefully we will not simply change places entirely, but meet in a harmonious middle, wa.