Meditation changes the sleeping brain | Mindfulness research roundup

Man sleeping on a bench
Distinctive electrical activity has been found in the sleeping brains of experienced meditators

This month’s roundup of mindfulness research features studies of meditation’s effects on the sleeping brain; mindfulness for hypertension; and mindfulness-based cognitive therapy for depression in adolescents.

Perchance to dream

Does meditation rewire the brain, changing the way it works? If so, you’d expect it to function differently all the time in experienced meditators, even when their brains are idling or in a “resting state”.

When researchers try to compare the resting brain activity of people who have been meditating regularly for years with those who have never practised it, though, they face a problem: at any particular moment meditators may be habitually dipping in and out of a meditative state or practising “mindfulness” whatever they happen to be doing, perhaps as a way to cope with stress and other mental challenges. This would seem particularly likely to happen in a strange laboratory as they are slid into an MRI scanner or have electrodes attached to their scalp.

What neuroscientists really want to do is compare brain activity when expert meditators and non-meditators have “switched off” completely.

One of the few times the mind lets go conscious control and attention is during sleep, so it provides a fantastic window into the brain’s “standby” mode or resting state. If the electrical activity of the brain is different in meditators and non-meditators even while they’re asleep, this would suggest the act of meditation has reconfigured or remodelled it in some way.

To find out, researchers at the University of Wisconsin-Madison in the US and the Lyon Neuroscience Research Center in France used a form of EEG (electroencephalography) to monitor the brain activity of meditators and non-meditators while they slept. The meditators had clocked up an average of 8,700 hours of Buddhist meditation, so they were highly experienced.

What they discovered was that the meditators had significantly stronger gamma waves in two lobes of the brain known as the parietal and occipital during non-REM sleep. (REM is the “rapid eye movement” phase of sleep when most dreaming takes place.)

The effect was big – there was a 50% difference in gamma power between the meditators and non-meditators.

The difference became more pronounced the more hours the volunteers had been practising, strongly suggesting that it was the meditation that caused the changes in brain activity rather than something else. Interestingly, the effect correlated with the hours spent in daily meditation but not with hours spent on meditation retreats.

During waking, gamma waves are associated with activities involving attention, learning and memory. The researchers believe the strong gamma signal among experienced meditators, “reflects the lasting, plastic effect on specific neuronal circuits of long-term meditation practice. For instance, the parietal cortex has been implicated in directing the focus of attention on a specific object [63], a cognitive skill perfected by attention-based meditation [1].”

The researchers further speculate that their results suggest experienced meditators retain some awareness during non-REM sleep. This is supported by other studies that have found meditation experts report more dreams, even in the deepest phases of non-REM sleep, than those who have never meditated.

It has been proposed that synchronised gamma waves play a role in coordinating brain activity to focus attention and create consciousness. There’s also a curious similarity between gamma wave synchrony during near death experiences (admittedly only detected in mice so far) and that in the brains of Tibetan monks as they meditate.

So in summary, this latest research adds further evidence that meditation has lasting effects on the plastic brain, and that gamma activity during non-REM sleep may be a reliable marker for the extent of these changes.

The results are reported in PLOS ONE.

Mindfulness and high blood pressure

Journalists and bloggers are often accused of focusing only on positive research results – the kind that win Nobel prizes by proving the researchers’ hypothesis (or disproving the null hypothesis if you want to be picky). Scientific journals can also be guilty of this kind of publication bias. The truth is that well-conducted studies throw up negative results all the time, and sweeping those results under the carpet seriously distorts the record.

So here’s a journal publishing some disappointing negative results. And this is a blogger reporting them.

Last month the American Journal of Hypertension published a study that looked at the effect on blood pressure of an eight-week course of mindfulness-based stress reduction in unmedicated, stage one hypertensive patients. There were 101 participants who were randomly assigned to two groups: one received MBSR, and the control group were put on a waiting list for the therapy.

There were no differences in outcome between the patients who took the mindfulness course and the controls. Average blood pressure readings went up slightly in both groups.

The jury is still out, of course. This month, the journal Psychosomatic Medicine published a study suggesting MBSR can reduce blood pressure in “pre-hypertension”. But this effect was only seen when the researchers looked at blood pressure readings taken in the clinic. It vanished when they analysed ambulatory blood pressure – a more reliable measure recorded as patients go about their everyday lives.

Interestingly, the study published last month – which found no benefit from MBSR – used ambulatory blood pressure readings.

Doctors are familiar with the phenomenon of “white coat hypertension”, whereby their mere presence can raise patients’ blood pressure in the consulting room as that strange inflatable cuff tightens around their arm. So for now it does rather look as though eight weeks of mindfulness training simply allows patients to “chill out” a bit better as they’re having their blood pressure measured.

Mindfulness for depression in adolescents

Rumination is recognised as one of the factors in the downward spiral of depression, both in adults and adolescents, so psychological strategies to minimise it – such as mindfulness training – are well worth investigating.

Mindfulness-based cognitive therapy (MBCT) is well established as a way to prevent relapse in adults prone to depression, with similar or better efficacy than cognitive therapy alone. However, until now it hasn’t been tested on groups of adolescents prone to depression, and previous studies of psychological therapies in general for adolescents with depression have had disappointing results.

This pilot study, published in Child and Adolescent Mental Health, appears to be the first to try out group MBCT sessions for adolescents. The paper, which is free to view in its entirety, provides excellent detail on the content and structure of the course, which should prove useful for any professional thinking about setting up and testing a similar course.

It was a small study (only 11 young people started the course) but the results are promising, with self-reported improvements in depression symptoms and mindfulness skills, and a reduction in rumination. The subjects enjoyed the course and appreciated its premise of fostering greater mindfulness and emotional awareness.

The London-based researchers are optimistic about the potential of MBCT for adolescents prone to depression, but they emphasise that their research is just the start of a long process to assess its efficacy :

These conclusions are made with a significant caveat, which is that with this low number of participants, the absence of a control group or full assessment of noncompleters, and follow-up only at 1 month, the data may reflect natural recovery rather than a meaningful and lasting response to treatment. Furthermore, future research might also consider the impact of mindfulness intervention with a greater number of male participants (given the predominance of female adolescents in this study) and deploy measures of treatment integrity. Therefore, these encouraging findings are seen to provide justification for future research and are informative about how best to adapt the adult MBCT course to suit the needs of young people.

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