Meditation isn't bliss all of the time, says cognitive and behavioral psychologist Dr. Paula Watkins, who is also a meditation expert. "It isn't all bliss and bountiful light," Watkins said on her website mindbodygreen.com. While studies have shown the benefits of meditation in reducing stress and improving overall health, meditation can also have a downside.

Meditation can also dredge up blocked memories and suppressed emotions that are overwhelming, she said. They are more likely to occur while undergoing intensive meditation, such as the eight to ten hours of daily meditation participants undergo for days at meditation retreats. The memories can trigger depression, anxiety, and make mental illness worse.

"Meditation is a means of relinquishing from the suffering of a chaotic and unstable mind," Watkins says, "but it must be noted that along the path there are going to be some moments of discomfort and mayhem in the process.

"People think intensive yoga and meditation retreats are all light, lovely and lucid," she said. "In reality, there can be some full-on ghastly moments.

"It’s not uncommon to hear retreat participants speak of tearful breakdowns, cold sweats, nightmares as well as moments of despair and loneliness."

She warns that those who are suffering from mental illnesses, such as schizophrenia, should not go to meditation retreats. When meditating, they and others who are working through emotional concerns, should be under the guidance of a qualified professional who could help if traumatic memories surface.

"It is not safe for them to be turning their attention inward unless they are meditating under the guidance of a registered health practitioner," Watkins told the Daily Mail. "Meditation is not a replacement for therapy."

However, fear of having a bad experience shouldn't cause people to turn from the relaxing benefits of meditation, she said. "For the bulk of people, meditation is absolutely beneficial and it helps us to relax, get calm, increases blood flow to the frontal lobe, and can even help cultivate compassion and empathy and a range of interpersonal benefits," she told the Daily Mail.