Here are two articles about people freaking out because of meditation. I’m not at all surprised. With so many wanting to strip meditation of its spiritual and/or religious aspects, it’s not surprising for people to have problems.
“Mindfulness therapy comes at a high price for some, say experts” http://gu.com/p/4x2ak
“The Dark Knight of the Soul
For some, meditation has become more curse than cure. Willoughby Britton wants to know why” http://www.theatlantic.com/health/archive/2014/06/the-dark-knight-of-the-souls/372766/
Meditation is bandied about as a cure-all performance enhancer (if your samadhi lasts more than 4 hours, see a doctor) and especially that it (along with yoga) is for “reducing stress.” It is actually for creating a certain kind of stress — just like lifting weights or running — that causes you to change and improve. So, without a qualified instructor, you are likely to strain your psyche badly. You don’t just go running willy-nilly around and lifting up heavy stuff without guidance and plan.
The very first, most important warm-up is leading a consciously ethical and moral way of life. Not just being a vaguely nice person, but trying hard to follow a code. That’s why there are precepts, pledges and vows. You don’t have to take them formally (but it’s awesome), you have to at least observe The Ten. The Buddha spent about half of His 50 year career talking about this, and the other half on meditation and wisdom. We Westerners only want the cool half. It’s like building a house without a foundation.