Most of these kinds of cases come out of the ten day Vipasanna meditation style where people sign up for ten day silent retreats which are intense beginning at 4 or 5 am and continuing until ights out at 10 pm.
So, the question is raised: "Can meditation be dangerous?" Here's a good answer to that question from Thubten Chodron in his book Buddhism For Beginners:
"If we learn to meditate from an experienced teacher who instructs us in a reliable method, and if we follow these instructions correctly, there is no danger at all. Meditation is simply building up good habits of the mind. We do this in a gradual fashion. Thus, doing advanced practices without proper instruction is unwise. If we build up our capabilities gradually, we will be able to progress to more advanced practices without difficulty, and one day will become a Buddha."