Vipassana is an _extremely_ powerful technique.. and not without its dangers - especially if you're not used to meditation. Check out http://livingvipassana.blogspot.com for a first hand account of a manic-depressive (bipolar) episode following it.

While no one knows the triggers to these things I would _not_ recommend just jumping in because you thought it'd be cool! Read up, do your research, and do lots of smaller practice before trying.

That'd be my recommendation anyway ;)