the risk of harm is low, but some people experience increased distress after mindfulness.
https://www.theguardian.com/lifeandstyle/2016/jan/23/is-mind...
There is definately some thing to gain and nothing to lose.
After 10+ years of working with this stuff in myself and others, I've learned to be very careful about what practices to undertake and what advice to offer others, so I won't share anything more here, but feel free to email me (address in profile) if you want some pointers.
This article is from a famous and long time Stanford Researcher on the same (who's also studying the effects of meditation on war veterans for quite some time along with other studies):
https://www.psychologytoday.com/blog/feeling-it/201309/20-sc...
http://www.newsweek.com/mindfulness-meaningless-word-shoddy-...
https://www.scientificamerican.com/article/wheres-the-proof-...
I have done two 10 day courses and served in one over the last four years and my first one almost 7 years ago. It was an experience of a lifetime. But be warned though, it is not for the casual lets-check-this-out minded. Do it if and when you’re serious about it.