Perhaps my view is scewed, but there is a Vipassana Centre here in the Blue Mountains. I work with the Psychiatric Emergency Team, and we have had to schedule (I think you call it "commit") as involuntary patients four people over three years who had their first psychotic episode while undertaking a ten day Vipassana course. One of them tried to kill their teacher with a mattock.
While there are disorders which mindfulness training seems to improve, it's not for everybody. For instance, two people with Borderline Personality Disorder may experience completely different reactions to mindfulness training, with one improving and the other worsening in symptoms.
From my experience and research, there are very few people who do not experience benefit from mindfulness meditation.
A great book on the subject is: Full Catastrophe Living, by Jon Kabbat-Zinn.
JKZ runs stress clinics all over North America wherein mindfulness meditation training is undertaken by people with a whole range of psychiatric disorders and physical pain.
There is also an interesting video called Doing Time doing Vipassana (Vipassana being mindfulness meditation) that features prison inmates going through intensive 10 day meditation training sessions with astounding results (eg prisoners being reformed, calling the parents of victims they murdered, hugging prison guards, understanding their pathological tendencies after years of living with them, etc).
Never underestimate the power of being silent!!
I would distinguish meditation/contemplation that develops mindfulness, on the one hand, and vipassana, on the other, which is a particular type of meditation/contemplation "which focuses on nonjudgmental awareness of sensations, feelings and state of mind", commonly anchored by bringing attention back to the breath. There are many meditation/contemplation practices that increase mindfulness (or "nepsis", in Greek), like lectio divina
, the Jesus Prayer, yoga, and singing devotional hymns.
However, a practice like vipassana, when divorced from its Buddhist context, involves mere breath awareness and noticing of thoughts and feelings. Such a practice would work best for people who are able to handle whatever thoughts and feelings arise. Such people may be emotionally healthy in general, or they may (also) have a committed spiritual/religious practice that allows them to place potent subconscious thoughts and feelings in a larger context. People who are emotionally unstable, or without an anchor in a spiritual tradition, would probably find vipassana less helpful than other sorts of meditations/contemplations. And, in fact, vipassana, and other sort of 'bare-bones' meditations/contemplations, may be detrimental for them.