It's November, the Monday before Thanksgiving, and David * is stuck in traffic on his way home from work.

Suddenly, while driving, has a revelation: everything that happens seems 'filtered' by his brain, entirely subjective, and perhaps entirely of his own invention.
He rolled down the window, turned on the radio, and slowly arrived home.
He was very tired, but every time I was about to fall asleep came a burst of energy to awaken him.
"One thing I've noticed, and in retrospect it is very clear, is that I am isolated," he says.
"I had nausea, pain in the stomach and chest, and a widespread existential terror," he says.
I had a job, a wife and two beautiful children, but I felt like I'd never felt joy in my life. "
But meditation should not be the oldest cure for the pain of our existence?
In addition to offering a 'secular' way of approaching spirituality, meditation also has a scientific basis and offers health benefits empirically demonstrated.
In some people it can cause permanent changes in personality and mood.
Willoughby Britton, director of the laboratory of neuroscience at Brown University, runs a support group for people like David-people for whom meditation is due to psychological and physical crisis.
Every week a growing number of people who contact to ask for help.
The group meets online, where people of all ages and backgrounds, from nine different time zones, seeking support in the company of other people affected by the negative effects of meditation.
More than 75 percent of the research on meditation does not take into account either measure side effects, says Britton.
Last year he published the largest study on issues related to meditation, interviewing 100 teachers and other enthusiasts with firsthand experience of these issues.
There hyperactivity: increased anxiety, fear, panic, insomnia, flashbacks related to trauma, and emotional instability.
It can also work on the contrary, you can try underactive form of dissociation and feeling of strangeness to his body, which is non-existent.
"Many speak of the absence of emotions far beyond the desired, and loss of motivation or pleasure," says Britton.
Ten years ago gave birth to Cheetah House, Association specialized in taking care of 'meditators' in difficulty.
(Managers app as Headspace Calm and they have not responded to my numerous requests for comment.)
As you can imagine, Britton is rather wary of the widespread use of meditation like a multi-vitamin.
"It seems to me that these programs, apps, or the people themselves who teach do not really take care of customers, and does not assume responsibility right," he explains.
"If people come to me, because it does not receive the necessary support from their meditation teacher."
"Nyams The term refers to a wide range of 'experiences meditative'-from joy, to visions, to the physical pain, mental disorders, including paranoia, sadness, anger and fear," Britton writes in his paper of 2017.
Some meditation experts call it "dark night," although the definition is also used in traditional Roman Catholic meditative, writes Shinzen Young, mindfulness teacher and consultant for neuroscience.
"It is almost certain that anyone who undertakes a serious meditation path must go through phases of negative emotions, confusion, disorientation, increased sensitivity to external and internal stimuli," Young wrote in 2011 in his blog.
What makes it problematic, however, it is that the person you usually plays as an adverse effect.
Instead of being a time of rediscovery and fullness, as would support the Buddhist literature, turns the opposite experience.
Young argues that for most people the experience is manageable with a competent teacher, and although they may take years to overcome it, the end result is usually "almost always extremely positive."
But for those who follow the practice in a superficial way, "the fall in the empty hole" is not a desirable situation.
* Patrick, 31 year old from Tennessee, read Wherever You Go, There You Are, Jon Kabat-Zinn and borrowed to the neighborhood library also audio-guide to meditation that accompanies the book.
He listened to the CD, with which he started practicing meditation and breathing body scan.
"About four or five times a week doing sessions from 30 to 45 minutes, and not a day passed that I meditate," he says.
"It's as if I had found the solution to live in peace and address the problems," he says.
At that moment began the concerns, he felt that if he continued to meditate would become a kind of zombies.
Patrick begins to feel very emotional, crying so much, and has to deal with intrusive thoughts.
He is convinced that it is something of the past that must have deeply disturbed and today is emerging to make him feel bad.
After discovering the Britton support group, she has begun to be seen by different doctors.
* Nick, 25, of Minnesota, he began to ponder after reading Waking Up: A Guide To Spirituality Without Religion, Sam Harris.
Last summer he began working as a volunteer in the center where they spent the retreat, meditating for three to four hours a day.
"I never imagined could happen anything wrong, since I had already made another in the past," he says.
Meditation did resurface painful memories of a traumatic car accident, lived 13 years.
"My mind was fixed on some parts of my body, and it was a very intense feeling," he says.
"I had several obsessive-compulsive tics, like every time I swallowed I heard a noise in the ear and remained stuck in this vortex swallowing-listen: I had interpreted as a problem and gave me a lot of noise and distraction."
After waiting about a month, hoping it would pass, Nick started to have suicidal thoughts.
When he came in contact with the group run by Britton, she has been advised to seek help.
And so he arrived in the emergency room, and remained hospitalized for about a week.
She lost her job after too many days of absence, and is now struggling to find a new one because of its intensive care program.
"I think that I would recommend everyone to try the guided meditation, a few minutes with the app," says Nick.
For people who have high emotional reactivity, this can be a positive thing.
It can have calming effect and reduce impulsive moments of responsiveness in everyday life.
"People interviewed in our research have complained about the total lack of emotions, both positive and negative, they do not feel love or affection for his family," says Britton.
There are many types of meditation, and Britton believes that each of these give the individual of different capacities.
Britton defines meditation as a set of activities that deepen intentionally some qualities of our body, of mind or behavior, even if, she recognizes itself, this definition could be applied to anything.
"The point is that here is intentional and has a specific goal, and to reach it you have to repeat the same action over and over again," he says.
Rebecca Semmens-Wheeler, a professor of psychology at Birmingham City Unity who studies hypnosis and meditation, think that contemporary trends have created a partial approach to meditation tradition.
The goal of mindfulness is not dissociated make, he says, and the fact to consider or just enjoy one of the many possible meditations is one of the main reasons that lead to complications.
"For the consumer it can be very confusing, but it is also problematic from the point of view of the search, when trying to understand what makes the mindfulness to the brain, and which has psychological effects," says Britton.
Richard Davidson, professor of psychology and psychiatry at the University of Wisconsin-Madison and founder and director of the Center for Healthy Minds, is known for his study on the benefits of meditation and other contemplative practices.
Since the start of our phone call, Davidson makes clear his respect for Britton as a scientist and a specialist.
"I think he's doing a great job bringing attention to these potential problems," he says.
Davidson, however, thinks that many of the people who are having negative effects have some pre-existing vulnerability, which was aggravated by the practice of meditation.
If I wanted to learn to do something complex, like playing the violin, I wonder, I think it would seek a teacher, right?
But we live in an age where people think they can find online all the answers they seek.
I could certainly learn to play the violin thanks to YouTube and a few apps.
However, when it comes to meditation, a practice that is aimed at changing the mind, it is better to be more cautious.
"I understand the need to find a shorter route, to achieve the results in less time, but if you really want to have mastered these skills, especially of such a complex such as meditation, it is best to have an experienced guide along the way," he explains.
When people are having negative side effects, says Davidson, it is difficult to understand what they have done to unleash them.
Britton tells me that Davidson's position is quite common: it only happens to people with pre-existing vulnerabilities.
The people in our study were teachers of meditation, and many of them, about half had elapsed or psychiatric events trauma in their past. "
All the people I contacted inside the Britton support group have asked to remain anonymous.
This is because they do not want their friends, bosses or family members discover their difficulties with the practice of meditation, generally considered curative.
"Mindfulness is seen as a positive practice, the panacea for all ills," says Sofia **.
The fact that we speak openly about how meditation has actually aggravated my symptoms would cause me shame and guilt.
Shortly after, Sophia had two severe panic attacks, had completely paralyzed the body and could not move.
For the 12 months following Sofia suffered from depersonalization and dissociation-the feeling of being separated from your body, not to have more self-awareness.
I would wake up, and it was not fear, it was terror, a truly difficult to understand and deal with. "
Many people, he says Sofia, when she tells of the problems encountered with meditation, tend to think that there was already something wrong with her.
"I come from the Middle East, I experienced the war, I was in a very abusive relationships, and I've never had these symptoms," he says.
"I've always been able to handle older trauma, but during the withdrawal have not been in grade to react, and it is the thing that surprises me even today."
We are not saying that previous psychiatric or trauma does not have any role, he explained Britton.
Mike *, 24 year old student from Boston, he explained that he had thought long and hard about the problem of pre-existing vulnerabilities.
According to him, it is true that there are people who start meditating but they get only exacerbate an injury or a disorder.
Mike has read two books by Jack Kornfield and began to meditate when he was 18, thanks to some friends.
He felt freer from the old insecurities and the narrative of himself as before.
"I remember that it was as if the reasons that I had given up at that time to be good have begun recently to seem important."
"My nervous system was as tangled, I was losing touch with myself and reality, I was into this void nihilist where things were happening and I could not understand them," he says.
When Mike found the search for Britton and got in touch with her, she was able to change perspective.
Rather than considering its symptoms as steps toward enlightenment, he began to see them as a way of its nervous system to respond to the practice.
"This is the most important thing for me, two different beings who connect in a special way," he says.
When he stopped meditating and began to reconsider their need for human relationships as a natural it has improved a lot.
They were advised meditation or mindfulness for almost every type of medical-anxiety, insomnia question, gastrointestinal problems, obsessive-compulsive and also for non-medical, such as eating or run.
"Some do it for life and they experience only the positive effects and the feeling of not having a body and never have a problem.
It's one thing not to be taken lightly, and able in certain circumstances to provide amazing benefits, and other do much harm.
As usually all types of meditation are gathered in one group without any distinction, we have not enough information about each type and its effects on the brain.
"There are hundreds of different meditation practices," says Davidson, "only a fraction of these have been studied scientifically, and were delivered in Western popular culture.
One of the main challenges of modern research is to determine more precisely which practices are recommended for the different types of people. "
But it could mean, for example, that if a practical meditation which increases introspection, for example the widespread practice of meditation body scan, in which remains in observation of any slightest sensation throughout the body, from head to foot, I found myself to have negative effects.
On the contrary, I might try the practice that trains the so-called exteroception, focusing on what's outside of my body.
"For me, the perfect mindfulness program is what allows people to try out the different processes, and to explore the various dimensions; that allows you to use your own mental power and your analytical skills to understand who you are, and to understand what are the practices that can help you achieve a better state of health, "says Britton.

From Vice