As a health journalist who writes about the science of the mind-body-health connection and who’s interviewed countless scientists on the subject, you would have thought that when I started making my new documentary about mindfulness, I would have known a thing or two. But just a few weeks into the endeavour I came across a study by neuroscientist Sara Lazar’s team at Harvard which changed everything and made me realise that I still had a lot to learn.

The study caught my attention because Lazar’s team had done a direct comparison of two of the most famous meditation programs in the U.S.; Herbert Benson’s mind-body Relaxation Response program and Jon-Kabat Zinn’s Mindfulness-Based Stress Reduction program. Both men are considered to have played a major role in laying the foundations for meditation’s proliferation in the West.

On the one hand there’s Benson, the renegade Harvard scholar who snuck Transcendental meditators through the back door of his lab in the late 1960s and discovered that his human guinea pigs were eliciting a “relaxation response,” opposite to the fight or flight stress response. More recently researchers at the Benson-Henry Institute for Mind-Body Medicine found that the technique could down-regulate genes associated with chronic inflammation.

On the other hand there’s Kabat-Zinn; the molecular biologist-turned mindfulness meditation teacher who developed an eight-week program in the late 1970s in order to help people with chronic illnesses who were falling through the cracks of a reductionist healthcare system. The program, which promises stress reduction by teaching people to approach their thoughts with non-judgmental curiosity and acceptance, has now been shown to benefit everything from anxiety and depression to quality of life and burnout, and is now embedded into the fabric of hospitals, schools and parliaments.

I met both Benson and Kabat-Zinn in 2014 when I was filming my previous documentary about the science of mind-body-health connection. (Extracts from my interviews with them are available here and here.) As someone diagnosed with an incurable autoimmune disease which flares during stress times of high stress, and also as a journalist who values evidence, meeting these scientifically-grounded meditation luminaries was transformative. They left me in no doubt that mind-body skills, such as meditation, would play an important part in medicine of the future.

But although both programs have now been running for 40 years, despite their long history, they had never been directly compared, until that is, Sara Lazar and her team at Harvard came along. Their study, which was published in the scientific journal Psychosomatic Medicine, put Mindfulness-Based Stress Reduction (MBSR) and the Relaxation Response (RR) program head to head for the first time.

It was a fascinating experiment because although the programs are both based on meditation, their scientific philosophies and meditative traditions have different foundations and subsequently, the instructions and exercises taught to students are also different.

Whereas the RR program focuses on reducing stress by deliberately eliciting a physiologic state of deep rest, the mindfulness program emphasises a particular non-judgmental attitude as its key to stress reduction. This is clear when you consider a meditation featured in both programs called a “body scan.” While relaxation response meditators are taught to systematically relax areas in their body, mindfulness meditators are taught to just be aware of each area, without trying to change anything.

The research team's scientific questions were simple; could the nuanced differences in these techniques result in divergent psychological and biological signatures? And if so, what would this mean for future mind-body health recommendations? After enlisting the support of experienced teachers and modifying the programs to match contact hours and assigned homework time, the researchers put them head to head using subjective wellbeing measures and objective fMRI brain scans.

Eight weeks later, the results revealed that there were both similarities and unique differences. Both groups reported a drop in perceived stress and both styles of meditation increased connectivity between brain regions associated with awareness of the physical body. But whereas the relaxation technique activated brain regions associated with deliberate control, the mindfulness technique activated areas associated with sensory awareness and perception. The mindfulness meditators additionally reported improvements in things such as self-compassion and rumination – two qualities that can reduce the risk of depression.

 “The relaxation response program is working more through deliberate control mechanisms, while the mindfulness program is working more through sensory-awareness mechanisms. It is somewhat analogous to weight training versus aerobic exercise — both are beneficial, but each has its unique mechanism and contribution,” the study’s lead author Gunes Sevinc, a research fellow in Lazar’s laboratory, told the Harvard Gazette.

All this was revelatory for me because I’d previously thought of various mind-body practices – from yoga and tai chi, to mindfulness, relaxation and Transcendental meditation – as variations of the same thing, which were all essentially aiming at stress reduction. And I’d thought that mindfulness was about learning to relax in order to trigger a response in my body that was opposite to stress.

What I now understood is that the word “meditation” is a bit like the word “exercise.” In the same way that swimming and running can both be good for me in similar and different ways, different mental training techniques have different effects.

Although emerging research is starting to further unlock some of the mechanisms of meditation, all this is not to say that the evidence is anywhere close to being able to prescribe specific meditation techniques, in specific doses, to specific people for specific purposes. For that, and for now, we’ll have to rely on experienced meditation teachers.

But for the purposes of my documentary experiment, which involved practicing mindfulness meditation every day for a year, the study helped me to understand why I was having so much trouble meditating. I couldn’t work out why I wasn’t feeling more relaxed. In fact, I was mostly finding the experience of sitting and noticing all my uncomfortable thoughts and feelings wholly unpleasant. What I now understood was that mindfulness wasn’t necessarily about relaxation at all, but rather about learning to be with whatever arises – be it pleasurable, painful, comfortable, or uncomfortable.

Stress reduction may have got me interested in mindfulness in the first place, but I was beginning to realise that I’d actually signed up for something that could turn out to be far more important.