I can't help thinking that most of these examples of negative side effects are related to intensives rather than meditation/mindfulness itself. There's a world of difference between 20 minutes a day and 10 days in a retreat looking inward. Maybe it's just better for you in short bursts, not long marathons. I once experienced negative effects after joining a Buddhist meditation group while at university. Every time I faced anything which provoked anxiety, such as preparation for my final exams, I would turn to meditation assuming it would help me get things done but it had the opposite effect of avoiding what I needed to face. I ended-up spending longer and longer periods meditating but I felt I was getting weaker both physically and neurologically. Eventually, during the end-of-term holiday break, I consulted a doctor who gave me tranquillisers for a few weeks and I left the Buddhist group when I returned to university but it took a while to get back to normal.
These days I do 20 minutes a day of mind control which involves nothing more than counting down from 9 to 1 repeatedly. No quest for Enlightenment. Just a sense of calm I can depend on balanced by facing stress and, most important, some kind of short-burst physical activity such as 3 sets of full squats to bring me right back into my body in no uncertain terms. Works wonders. It's all about balance. 10-day mindfulness retreats full of 2-hour sessions, in my view, are for zealots.
These days I do 20 minutes a day of mind control which involves nothing more than counting down from 9 to 1 repeatedly. No quest for Enlightenment. Just a sense of calm I can depend on balanced by facing stress and, most important, some kind of short-burst physical activity such as 3 sets of full squats to bring me right back into my body in no uncertain terms. Works wonders. It's all about balance. 10-day mindfulness retreats full of 2-hour sessions, in my view, are for zealots.