Is yoga, meditation and breathing exercises dangerous?

Read these quotations from different sources.

Vipassana Meditation - The lights I was seeing were to many

"I noticed a throbbing in my head, tinnitus, and feeling dizzy and like the whole world became a nightmare. "

I was meditating and followed the Silva mind control technique

"2 years of almost an animal life, I couldn't eat, have sex, even speak was a great deal to me, spending months, or days, in mental institutions, telling my "kundalini story" (yeah, sure !!) to the doctors."

Public letter to Mr. Deepak Chopra

".....I have a wish that you and the other gurus and teachers would take some responsibility in what you are teaching people. Those who have been damaged by these dangerous artificial exercises have no one to turn to when they have been struck by the tremendous kundalini energy."

Hatha Yoga and its dreadful effects

"There also was like a black force that was mesmerizing me. Exactly as if it was a snake, a devil. I was attracted by it and I wasn't realizing I was destroying myself."

Hassled by spirits

"I got stuck in Delhi helping bad souls. Lost control, went mad, while trying to work through it with the Indians. Some one got me back to England, there I felt I was an empty vessel being controlled by other people."

Kundalini and Siddha Yoga

A story of Kundalini arousal in Siddha Yoga and the hard consequences. Kundalini energy can be very dangerous.

When the Serpent Bites

"On May 5th 1999 the energy erupted waking me up, I hadn't emitted semen for about two weeks so it was very powerful (in hindsight this was the main contributing factor) and with a great amount of energy it rocketed straight up to the brain, not traveling in the central channel, where it smashed through the block protecting the brain."

Kundalini & Breathing Exercises

Rebirthing and other breathing exercises can cause explosive Kundalini experiences, psychosis and other mental diseases.

Dangers of Cathartic Breathwork

"To make a long story short, it was during these weekly underwater breaths that I "lost my mind". It happened one night when I lay down to sleep. I distinctly had the impression of an alien force taking over my thoughts. I sprang from the bed, terrified."

Kundalini and Transcendental Meditation

"When I had meditated for about ten minutes a scary silence entered my inner self. The silence was awesome, it was like entering into a black hole in outer space. My heart almost exploded and a bright light engulfed me with such power that I levitated. It was like diving into the sun."

My Enlightenment Delusion - experiences and musings of a former Transcendental Meditation teacher

"I am offering my conjectures based on my analysis and based on the experience of my 1990 “kundalini crisis” that occurred after fervently chasing enlightenment for 18 years.
During my kundalini crisis, I had commonplace symptoms of psychotic mania such as excited mental states, euphoria, delusions, and over-confidence..."

Osho Meditation

"At first, it was great. I began to change, inside and out. I'm telling you, even my physical appearance was different. My eyes... I became like the classic spiritualist-frail, beautiful, and to tally reliant. [...] Then, in a moment, everything went wrong..."

The Safety of the Heart

"There are many Kundalini casualties similar to mine. Kundalini energy literally crippled me mentally in terms of what academic achievements and future accomplishments I may have had. Some people it has destroyed."

A Strange-But-True Spiritual Journey

"Spirit guides, meditation, astrology, the "higher Self," raising the kundalini, developing psychic abilities, praying to gurus, astral travel, numerology, Tarot cards, contacting the dead, hanging out with witches, Sufis, followers of Muktananda, Rajneesh, Sai Baba, Maharaji, -- all these and more were part of my journey. How did I get on this path?"

A Simple, Natural, Relaxation Technique?

"I'd like to relate a few of my adventures from my years as a TM meditator and teacher."

The Tragedy of Falun Gong Practitioners

"Liu Siying, a 12-year-old girl, soaked herself with gasoline and set herself on fire on January 23. She suffered severe burns to her face, head and hands. Doctors said all her fingers may have to be amputated, according to the latest issue of the Beijing Review."

Qi-Gong Psychotic Reaction

"I was able to find one case report of qi-gong reactive psychosis. Lim & Lin (1996:369ff) describe a 57-year-old Chinese-American man who presented with a three-week history of auditory and visual hallucinations. The patient had begun qi-gong practices as therapy for chronic problems with kidney stones. After several days of intensive qi-gong, he began hearing voices telling him how to practice qi-gong, and to believe that he had contacted beings from another dimension. He sought help from the qi-gong masters, but to no avail. His wife brought him to see a psychiatrist, who diagnosed him with schizophreniform disorder and treated him with anti-psychotic medications. Additional information on qi-gong psychotic reaction has not been readily available. The majority of information on qi-gong itself is to be found in journals of acupuncture and homeopathic medicine."

The single case report I could find is:
Lim, Russell F., and Lin Keh-Ming. (1996) "Cultural formulation of psychiatric diagnosis: Case No. 03: Psychosis following qi-gong in a Chinese immigrant." Culture, Medicine, and Psychiatry 20:369-378.

DSM-IV , the standard US psychiatric diagnostic manual, now contains a diagnostic category called "Qigong-Induced Psychosis":

"qi-gong psychotic reaction A term describing an acute, time-limited episode characterized by dissociative, paranoid, or other psychotic or nonpsychotic symptoms that may occur after participation in the Chinese folk health-enhancing practice of qi-gong ("exercise of vital energy"). Especially vulnerable are individuals who become overly involved in the practice. This diagnosis is included in the Chinese Classification of Mental Disorders, Second Edition (CCMD-2). "

Qigong Deviation Syndrome

"The common symptoms in mental disturbance are anxiety, nervousness, depression, etc. Seriously ill patients cannot control their own behavior. Some patients are found to have hallucination or delusion, and some even have the impulse of committing suicide."