The Dark Night Project at Brown University has been investigating some common psychological issues that can arise with many people who set out on the meditation path. Common problems include those who enjoyed that sense of enhanced sensual awareness on a retreat but then found the sensory overload alarming in everyday life; disorienting experiences of depersonalization; and manic emotional states. As the effects can last for some years the neuroscientists at Brown University are trying to find out why some people find meditation plain sailing while others enter the "dark night".
(The link is to the second of two transcripts but it deals more usefully with the problems that can arise following meditation than the first interview which is more background info.) http://www.buddhistgeeks.com/2011/09/bg-232-the-dark-night-project/ http://www.buddhistgeeks.com/2011/09/bg-232-the-dark-night-project/