Studies have shown yoga to be beneficial for both physical and mental health, but the biological mechanisms for why have been poorly understood -- until now. New research from the University of Oslo has determined that yoga practices can have an almost immediate impact on gene expression, particularly in immune cells.


From previous research , we know that yoga is linked to not only lower stress levels, but also bone health, reduced back pain, relief from depression, and lower risk factors for heart disease, among other health benefits. However, the means by which these positive effects are enacted have been poorly understood.


The Norwegian study, published this month in the journal PLOS ONE , has found genetic evidence of yoga's impact on the immune system. In the study, researchers examined 10 participants who underwent a week-long yoga retreat where they did meditation, yogic postures and yogic breathing exercises. Examining the participants' blood before and after four-hour yoga sessions showed that the yoga practice changed the expression of 111 genes in circulating immune cells. In contrast, music and walking-based relaxation changed the expression of 38 genes.


"There are rapid (within two hours of start of practice) and significant gene expression changes... during a comprehensive yoga program," the research team writes in the study. "These data suggest that previously reported effects of yoga practices have an integral physiological component at the molecular level which is initiated immediately during practice and may form the basis for the long-term stable effects."


The results suggest that yoga may as effective, or even more so, than traditional exercise in inducing health benefits through changes on the genetic level, the study's authors note.


And although it's long been known that yoga can reduce stress, a UCLA study also recently determined how the practice can induce relaxation. Practicing a type of chanting yogic meditation daily for eight weeks was found to lower stress levels by reducing biological mechanisms responsible for increasing the immune system's inflammation response -- and stress is known to spur inflammation.


Looking to combat stress through yoga? Click here for an instructional guide to the best tension-busting yoga poses, and click here for "off-the-mat" stress-reduction tips from a yoga expert.


LOOK: The best yoga poses for stress relief:






  • Child's Pose (Balasana)


    The calming child's pose is a resting posture that can help quiet the mind, easing stress and anxiety while gently stretching the back. It's also good for the nervous system and lymphatic system, Kennedy notes. "It's one of the key poses that you can come to in the middle of a class whenever you want to to relieve stress," she says. "It's very restorative ... it's child-like and allows us to come inward to ourselves."




  • Bridge Pose (Setu Bandha Sarvangasana)


    Not to be confused with the <a href="http://www.yogajournal.com/poses/473" target="_blank">full wheel</a>, the bridge pose provides gentle stretching of the back and legs while alleviating stress and tension. The pose can reduce anxiety, fatigue, backaches, headaches and insomnia, and is even thought to be therapeutic for high blood pressure. Eva Norlyk Smith, Ph.D., yoga teacher and Managing Editor at YogaUOnline, recommends a supported bridge pose with a block underneath the sacrum as a gentler and more de-stressing way to enjoy the stretch.




  • Standing Forward Bend (Uttanasana)


    Often used as a transition between poses, uttanasana has many benefits when practiced as a pose in itself. The posture stretches the hamstrings, thighs, hips, and is thought to relieve stress, fatigue and mild depression. If your goal is to de-stress in the pose, it's best done with the knees slightly bent, Kennedy says. "It's great for the legs and a lot of different physical things, and it also allows us to calm the mind. You're reversing the blood flow and just hanging out," she says.




  • Eagle Pose (Garudasana)


    The active and empowering eagle pose can help ward off stress by improving concentration and balance, and also by opening up the shoulders, upper back and hips. "Eagle is an empowerment pose because it releases tension in the shoulders, legs and back, and it does require focus for you to remain balanced in it," says Kennedy. "You're literally squeezing the tension out of the body. It's a very active de-stress move"




  • Corpse Pose (Savasana)


    Most yoga practices end with several minutes spent in savasana, and it can easily be the most calming part of the whole thing. The pose puts the body completely at ease and emphasizes total relaxation. Savasana can trigger the body's "relaxation response," a state of deep rest that slows the breathing and lowers the blood pressure while quieting the nervous system. "[Savasana] is <em>the</em> relaxation pose," Kennedy says. "It's actually difficult for many people because we're so not used to being still ... But it encourages the body to come to a more restful state."




  • Extended Triangle Pose (Utthita Trikonasana)


    One of the foundational postures, the triangle pose is an excellent stress-reliever and full-body stretch, <a href="http://www.yogajournal.com/poses/494" target="_blank">according to Yoga Journal</a>. It can also help to improve digestion, and potentially mitigate the symptoms of conditions like anxiety, osteoporosis and sciata.




  • Legs-Up-The-Wall Pose (Viparita Karani)


    Norlyk Smith recommends the resting legs up the wall pose for stress reduction. The pose is traditionally thought to <a href="http://www.yogajournal.com/poses/690" target="_blank">slow the aging process</a>. "It helps renew blood and lymph drainage back into the heart area," she says.




  • Puppy Pose (Uttana Shishosana)


    A variation of child's pose with a heart-opening effect, this mild inversion pose can help to counter our tendency to crouch and slouch the shoulders when stressed, according to Norlyk Smith.




  • Cat Pose (Marjaryasana)


    The cat pose soothes and stretches the lower back, relieving stress while gently massaging the spine. Try arching and rounding the back 10 times in a row while focusing on deep inhaling and exhaling. "[In the cat pose], you're releasing stress in the spine ... If you're in a class, it allows students to begin to slow down and focus on the breath," Kennedy says. "It's one of those transition poses that takes us from the outside world in."




  • Dolphin Pose


    Similar to the downward-facing dog position, except with the forearms on the floor, his standing inversion pose can help to quiet the mind, alleviate stress and reduce anxiety, <a href="http://www.yogajournal.com/poses/2462" target="_blank">according to Yoga Journal</a>. The posture stretches the shoulders, neck and spine.