The patients are sitting still, their eyes closed, meditating, on the floor of a group therapy room at the Centre for Addiction and Mental Health in Toronto.
It is the fifth week of an eight-week training course in mindfulness meditation for people recovering from depression.
Their goal is to treat any troubling thoughts or emotions with the same detachment with which they monitor the breath flowing in and out of their bodies.
Mindfulness-based psychotherapy is growing rapidly in popularity, and these patients are part of a $2.5-million clinical trial to assess whether it can prevent relapses as effectively as antidepressant medications.
Zindel Segal, a psychologist at CAMH, is a pioneer in the field of assessing the value of mindfulness meditation as a treatment for mental illness.
He is also studying how it physically changes the brain in ways that may be helpful to people recovering from depression or anxiety disorders.
"Depression and anxiety disorders tend to have a chronic, unremitting course," Dr. Segal says.
"So prevention of relapse is as important as lifting patients out of an acute episode."
Mindfulness meditation builds on the teachings of a fifth-century BC Indian prince later known as Buddha. It involves sitting still, with eyes closed, relaxing, and taking note of bodily sensations; the pressure of the floor on your foot, your tummy rising as you breathe. When a person's attention wanders, they are instructed to redirect it back to their breathing.
Once people can do this, Dr. Segal says, they can turn their attention to a troubling thought - an ugly breakup of a romantic relationship, for example. The idea is to endure and accept difficult emotions without trying to change them, to view passing thoughts as an impartial observer.
"It helps you step back from automatic reactions built into emotions for evolutionary reasons," he says. "Fright, alarm, rejection are experiences that can come over us very quickly."
Pausing at these moments can be helpful for people with a history of depression, he says. They can label and observe emotions rather than automatically reacting.
But there are not a lot of studies that show mindfulness training works as a treatment for mental illness.
The clinical trial now under way is being funded by the National Institutes of Health in the United States and involves 177 patients in Toronto and Hamilton. They have all been successfully treated with antidepressants.
Patients in one group are still on their medication. In the second group, people who have been weaned off antidepressants are getting a placebo. In the third, patients are no longer taking medication but have undergone eight weeks of mindfulness training.
The clinicians following the patients don't know which group they are in. Dr. Segal should have preliminary results in 18 months.
In one mindfulness session, taped as part of the experiment's protocol, a female therapist explains to a group of patients the idea that they could accept troubling or difficult thoughts in the same way parents can love their children despite their sometimes challenging or even outrageous behaviour.
The patients get comfortable on the floor, and she guides them to pay attention to their breathing. She tells them not to banish any thoughts, but to accept them for what they are.
Afterward, one patient says she found the process less intense than the week before.
But another patient, fighting back tears, says she found the session difficult. She says she feels bad about fidgeting and not paying attention.
"I was bothered by pain, and physically uncomfortable."
Dr. Segal knows it isn't easy. He tries to practise meditation himself every morning, and says many doctors find they can guide patients more easily if they have personal experience.
The patients in the trial are also asked to meditate every day at home, and are given CDs to help them.
Dr. Segal, who holds the Morgan Firestone Chair in Psychotherapy at the University of Toronto, became interested in mindfulness meditation in the early 1990s, after University of Massachusetts biologist Jon Kabat-Zinn found that it helped patients with chronic pain.
At the time, Dr. Segal was investigating how psychological treatments such as cognitive behavioural therapy work in patients with depression.
Cognitive behavioural therapy is talk-based therapy that teaches participants new ways of thinking and behaving to overcome negative thought patterns and manage their symptoms.
Studies have shown it can prevent relapses as well as antidepressants can, and Dr. Segal and other scientists have found it can lead to physical changes in the brain.
He thought a version of CBT based on mindfulness meditation might offer patients an advantage, but was worried about being dismissed by his colleagues as being on the fringe of science.
"We didn't call it mindfulness. We called it attention control training," he says.
That was a decade ago, and since then he and other researchers have made intriguing discoveries about mindfulness meditation. Richard Davidson, an American neuroscientist, has done brain scans of Tibetan monks and found they have more activity in their left prefrontal lobes, an indication of positive emotions and good mood.
Dr. Segal wants to know how it changes the brains of people with mood disorders. "To them, returning to normal moods is an important goal."
He and colleague Adam Anderson, a psychologist at the University of Toronto, recently reported the preliminary results of a study done at St. Joseph's Health Centre in Toronto.
It involved two groups of patients suffering from depression, anxiety or chronic pain. One group had taken eight weeks of mindfulness training.
The patients watched and reflected on scenes from sad movies, such as Terms of Endearment, while a functional magnetic resonance imager took a picture of their brains.
While all the patients reported feeling sad after watching the tear-jerker scenes, the brains of those who had undergone mindfulness training responded differently.
The training seemed to quiet parts of the brain that respond to negative emotion with rumination and self-judgment, but to activate another region that integrates information about heart rate, posture and movement.
"There was more of a balance," Dr. Segal says.