About the Research Databases

The Wellness Evidence team of doctor consultants selected four of the most respected evidence-based medicine databases that are also particularly useful for wellness-focused research: Natural Standard, The Cochrane Library, PubMed and the TRIP Database.

Please read “Important Things to Know,” including info on each database.

We’ve made researching a particular therapy simple by pre-searching the evidence at each database. (See evidence below.) However, please note that evidence-based medicine relies on a research hierarchy, because not all evidence is created equalLearn more about how the medical experts classify this research.

We’d like to hear from you. If there is a Wellness Evidence discipline you would like to see on these pages, please email us.

Natural Standard

An international research collaboration that systematically reviews (and limits its focus to) scientific evidence on complementary and alternative medicine (CAM). Founded in 2000, Natural Standard assigns a grade to each CAM therapy, reflecting the level of available scientific data for or against the use of each therapy for a specific medical condition.

Natural Standard is subscription-based, and each of the database’s monographs aggregates data from other resources like AMED, CANCERLIT, CINAHL, CISCOM, the Cochrane Library, EMBASE, HerbMed, International Pharmaceutical Abstracts, Medline and NAPRALERT – and 20 additional journals. Data analysis is performed by healthcare professionals conducting clinical work and/or research at academic centers, using standardized instruments pertaining to each monograph section


Yoga is an ancient system of relaxation, exercise, and healing with origins in Indian philosophy. Early descriptions of yoga are written in Sanskrit, the classical literary language of India. The first known work is “The Yoga Sutras,” written more than 2,000 years ago, although yoga may have been practiced up to 5,000 years ago. The initial concepts have been adapted over time through translation and scholarly interpretation, but the fundamental principles describing the practice of yoga in the quest of the soul remain largely intact.

Yoga has been described as “the union of mind, body, and spirit,” which addresses physical, mental, intellectual, emotional, and spiritual dimensions towards an overall harmonious state of being. The philosophy of yoga is sometimes pictured as a tree with eight branches. These eight limbs are: pranayama (breathing exercises), asana (physical postures), yama (moral behavior), niyama (healthy habit), dharana (concentration), prathyahara (sense withdrawal), dhyana (contemplation), and samadhi (higher consciousness). There are several schools of yoga practice, such as hatha yoga, karma yoga, bhakti yoga, and raja yoga. These schools vary in the proportions of the exercises of the eight limbs. However, they are all similar in working towards the goal of self-realization and control of mental, physiological, and psychological parameters through yogic experiences. In the United States and Europe, hatha yoga is commonly practiced, including pranayama and asanas.

Yoga is often practiced by healthy individuals with the aim to achieve relaxation, fitness, and a healthy lifestyle. Yoga has also been recommended and used for a variety of medical conditions. Yoga techniques can be learned in classes or through videotape instruction. Classes last from 30 to 90 minutes and are offered at various skill levels. There is no widely accepted credentialing for yoga instructors.

Evidence Table
The grades A-F ascribed to the specific health conditions below have a very specific meaning. i.e., a “C” can still mean evidence of benefit from a small randomized trial, etc. Read about what each grade actually means. Grade
Multiple human studies report benefits of yoga (such as breathing exercises) when added to other treatments for mild-to-moderate asthma (such as standard drug therapy, diet, or massage).
High blood pressure
Several human studies support the use of yoga in the treatment of high blood pressure when practiced for up to one year. It is not clear if yoga is better than other forms of exercise for blood pressure control. Yoga practitioners sometimes recommend that patients with high blood pressure avoid certain positions, such as headstands or shoulder stands (inverted asanas), which may increase blood pressure.
Altitude sickness
Yoga uses controlled breathing patterns to increase breathing efficiency. More research is needed before a recommendation can be made.
Several human studies support the use of yoga therapy in the treatment of clinical anxiety disorders and in otherwise healthy individuals with anxiety. Additional well-designed studies are needed before a strong recommendation can be made.
There is promising early evidence that yoga therapy may help treat both osteoarthritis and rheumatoid arthritis. More research is needed to confirm these results.
Carpal tunnel syndrome
Yoga therapy has been studied for carpal tunnel syndrome, but it is not clear if there are beneficial effects. Further research is needed before a recommendation can be made.
Several human studies support the use of yoga for depression in both children and adults. Although this preliminary research is promising, better studies are needed.
Heart disease
Several human studies suggest that yoga is helpful in people with heart disease. However, it is not clear if yoga reduces the risk of heart attack or death or if yoga is better than any other form of exercise therapy or lifestyle/dietary change. Therefore, yoga may be a useful addition to standard therapies (such as medications for blood pressure or cholesterol) in people at risk for heart attacks, but further research is necessary before a strong recommendation can be made.
Lung disorders
Limited adult human study exists for the treatment of lung conditions such as bronchitis, fluid around the lungs (pleural effusion), or airway obstruction. Better-designed research is necessary before any firm recommendations can be made.
Obsessive-compulsive disorder
Several human studies support the use of yoga therapy in the treatment of obsessive-compulsive disorder (OCD). Additional well-designed studies with clearly defined patient groups are needed before a strong recommendation can be made.
Quality of life
Yoga may be beneficial for improving the quality of life for patients with serious diseases as well as in healthy patients. Several studies in cancer patients report enhanced quality of life, lower sleep disturbance, decreased stress symptoms, and changes in cancer-related immune cells after patients received relaxation, meditation, and gentle yoga therapy. Higher quality studies are needed.
Several human studies support the use of yoga therapy in the treatment of schizophrenia. Additional well-designed studies with clearly defined patient groups are needed before a strong recommendation can be made.
Seizure disorder (epilepsy)
Several human studies report a reduction in the number of monthly seizures with the use of Sahaja yoga, when it is added to standard anti-seizure drug treatment or a yoga meditation protocol. This research is preliminary and better studies are necessary before a firm conclusion can be drawn.
Substance abuse
Preliminary research suggests that yoga may be beneficial when added to standard therapies for the treatment of heroin or alcohol abuse. Additional studies are needed before a strong recommendation can be made.
Yoga may have antioxidant properties. More, higher quality evidence is needed to confirm these results.
Attention deficit hyperactivity disorder (ADHD)
There is limited study in humans of yoga in the treatment of attention deficit hyperactivity disorder (ADHD). Further research is needed before a recommendation can be made.
Several preliminary human studies suggest that daily yoga may improve control of blood sugar levels in people with type 2 diabetes when it is added to standard drug therapy. It is not clear if yoga is better than any other form of exercise therapy. Better research is needed before a recommendation can be made.
Eating disorders
There is unclear evidence in this area.
Preliminary studies in humans report that yoga may improve fatigue in adults. However, better-designed studies are needed before any conclusion can be made.
Preliminary evidence suggests that yoga may effectively reduce the intensity and frequency of tension or migraine headaches and lessen the need for pain-relief medications. Better studies are needed before a recommendation can be made.
Preliminary research reports that yoga may benefit sleep efficiency, total sleep time, number of awakenings, and quality of sleep. Well-designed research is necessary before a firm recommendation can be made.
Irritable bowel syndrome (IBS)
Early evidence suggests that yoga may be beneficial in the management of IBS. Further research is needed to make a recommendation.
There is limited human study of yoga to improve memory. Most research focuses on memory in children. Better studies are needed before a recommendation can be made.
Menopausal symptoms
Early evidence showed mixed results regarding yoga’s effect on menopausal symptoms. Although early results are promising, more research is needed in this area.
Mental retardation
There is limited human study of yoga therapy in children with mental retardation. Better trials are needed to confirm these results and to evaluate the effects of yoga in mentally retarded adults.
Multiple sclerosis (fatigue, cognitive function)
There is limited study of yoga therapy in patients with multiple sclerosis. Further research is needed before a recommendation can be made.
Muscle soreness
There is limited study in humans of yoga for improving muscle soreness. Further research is needed before a recommendation can be made.
Preliminary research reports that yoga may improve chronic low back pain in humans. However, larger better-designed studies are needed before a firm conclusion can be drawn.
Performance enhancement
Preliminary studies in humans report that yoga (mukh bhastrika) may improve human reaction time, arousal, information processing, running performance, and concentration. Further research is needed before a clear recommendation can be made.
Posture (children)
Preliminary human study suggests that yoga may improve physical posture. Better-designed studies are needed before a conclusion can be drawn.
Early research suggests yoga during pregnancy is safe and may improve outcomes. Additional research is needed before a clear recommendation can be made. Pregnant women who wish to practice yoga should discuss this with their obstetrician or nurse-midwife.
Ringing in the ears (tinnitus)
It is unclear whether yoga therapy may improve tinnitus. Although relaxation may theoretically benefit this condition, additional research is needed before a recommendation can be made.
Slow (delayed) ejaculation
There is early evidence to support the use of yoga in the treatment of delayed ejaculation in males. Larger well designed and controlled trials are needed to further assess the effects of yoga for sexual health.
Preliminary study suggests possible benefits of a yoga-based exercise program on people who have had a stroke and have impaired health status and reduced level of activity. Although results seem promising, further well-designed research is needed to confirm these findings.
Weight loss/obesity
Preliminary research does not provide clear answers. Yoga in addition to healthy eating habits may reduce weight. Better studies are necessary to form conclusions about the potential benefits of yoga alone.

Yoga techniques use gravity, leverage, and tension while holding poses for varying lengths of time. Ancient texts describe rapid breathing (kapalabhati) as cleansing and stimulating and slow breathing (nadisuddhi), particularly through alternate nostrils, as calming.

Yoga has undergone much scientific study, with various psychological and physical theories suggested. In human research, yoga has been shown to reduce heart rate and blood pressure, increase breath holding time and lung capacity, improve muscle relaxation and body composition, cause weight loss, and increase overall physical endurance. Yoga may positively affect levels of brain or blood chemicals, such as monoamines, melatonin, stress hormones (cortisol), and GABA (gamma aminobutyric acid). Changes in several mental functions, including perception, attention, cognition, processing of sensory information, and visual perception, are described in human research.

It is proposed that health may be affected by mind-body interactions that occur through techniques such as yoga, and that daily practice of yoga may help to maintain wellness.


The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Alzheimer’s disease, anemia, anticoagulant (blood thinner), anti-inflammatory, cancer, chronic urological disorders, cognitive enhancement, constipation, dementia, dyspepsia (upset stomach), dyspnea (difficulty breathing), fibromyalgia, hand grip strength, heart attack treatment/prevention/rehabilitation, high cholesterol, HIV/AIDS, hormonal abnormalities, hypoxemia (low oxygen in the blood), immune stimulant (in breast cancer patients), infertility, joint pain or stiffness, osteoporosis, post-traumatic stress disorder (PSTD), premenstrual syndrome (PMS), psychological stress, psychosomatic disorders, rehabilitation, rheumatoid arthritis, seasonal affective disorder (SAD), sensory integration disorder, sex offender rehabilitation, sex therapy, shortness of breath, smoking cessation, speech disorders (vocal cord dysfunction), spine problems (scoliosis), stomach upset, stress (occupational, oxidative), thyroid disease, tuberculosis.


Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.

Yoga is generally considered to be safe in healthy individuals when practiced appropriately, and it has been well tolerated in studies with few side effects. Yoga can be adapted for a wide variety of specific needs, including for people who are bed-ridden or wheelchair-bound. Yoga techniques are believed to be safe during pregnancy and breastfeeding when practiced under the guidance of expert instruction (the popular Lamaze techniques are based on yogic breathing). However, poses that put pressure on the uterus, such as abdominal twists, should be avoided in pregnancy.

Some positions and postures should not be used by people with certain conditions or illnesses. Therapy should be exercised under well-qualified guidance. Patients with disc disease of the spine, fragile or atherosclerotic neck arteries, risk for blood clots, extremely high or low blood pressure, glaucoma, detachment of the retina, ear problems, severe osteoporosis, or cervical spondylitis should avoid some inverted poses. Certain yoga breathing techniques should be avoided in people with heart or lung disease. Some experts advise caution in people with a history of psychotic disorders (such as schizophrenia), due to a risk of worsening symptoms, although this has not been clearly shown in studies. People with medical conditions should speak with a qualified healthcare professional before starting yoga.

Rare side effects are described in case reports, including physical damage (due to prolonged postures), nerve or vertebral disc damage (due to prolonged postures, sometimes involving the legs), eye damage and blurred vision including worsening of glaucoma (due to increased eye pressure with headstands), and stroke/blood vessel blockage (due to decreased blood flow to the brain or other body parts from postures). Lung and breathing problems have been reported possibly resulting in death.

Yoga should not be used as a substitute for standard care, especially for potentially dangerous ailments such as asthma. Patients should seek the guidance of a qualified healthcare provider before embarking on any regimen of treatment.


This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com): Dawn Costa, BA, BS (Natural Standard Research Collaboration); Cynthia Dacey, PharmD (Natural Standard Research Collaboration); Nicole Giese, MS (Natural Standard Research Collaboration); Jill M. Grimes Serrano, PhD (Natural Standard Research Collaboration); Carolyn Williams Orlando, MA (Natural Standard Research Collaboration); Shaina Tanguay-Colucci, BS (Natural Standard Research Collaboration); Catherine Ulbricht, PharmD, MBA[c] (Massachusetts General Hospital); Minney Varghese, BS (Northeastern University); Wendy Weissner, BA (Natural Standard Research Collaboration); Jen Woods, BS (Natural Standard Research Collaboration).


Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. Selected references are listed below.

  1. .Bower JE, Woolery A, Sternlieb B, et al. Yoga for cancer patients and survivors. Cancer Control 2005 Jul;12(3):165-71.
  2. Cohen BE, Kanaya AM, Macer JL, et al. Feasibility and acceptability of restorative yoga for treatment of hot flushes: a pilot trial. Maturitas 2-20-2007;56(2):198-204.
  3. Duraiswamy G, Thirthalli J, Nagendra HR, et al. Yoga therapy as an add-on treatment in the management of patients with schizophrenia–a randomized controlled trial. Acta Psychiatr Scand 2007;116(3):226-232.
  4. Garfinkel MS, Singhal A, Katz WA, et al. Yoga-based intervention for carpal tunnel syndrome: a randomized trial. JAMA 11-11-1998;280(18):1601-1603.
  5. Garrow D, Egede LE. Association between complementary and alternative medicine use, preventive care practices, and use of conventional medical services among adults with diabetes. Diabetes Care. 2006 Jan;29(1):15-9.
  6. Granath J, Ingvarsson S, von Thiele U, et al. Stress management: a randomized study of cognitive behavioural therapy and yoga. Cogn Behav Ther 2006;35(1):3-10.
  7. John PJ, Sharma N, Sharma CM, et al. Effectiveness of yoga therapy in the treatment of migraine without aura: a randomized controlled trial. Headache 2007;47(5):654-661.
  8. Kirkwood G, Rampes H, Tuffrey V, et al. Yoga for anxiety: a systematic review of the research evidence. Br J Sports Med 2005 Dec;39(12):884-91; discussion 891.
  9. Mitchell KS, Mazzeo SE. Rausch SM, et al. Innovative interventions for disordered eating: evaluating dissonance-based and yoga interventions. Int J Eat.Disord 2007;40(2):120-128.
  10. Oken BS, Zajdel D, Kishiyama S, et al. Randomized, controlled, six-month trial of yoga in healthy seniors: effects on cognition and quality of life. Altern Ther Health Med 2006 Jan-Feb;12(1):40-7.
  11. Rao MR, Raghuram N, Nagendra HR, et al. Anxiolytic effects of a yoga program in early breast cancer patients undergoing conventional treatment: a randomized controlled trial. Complement Ther Med. 2009 Jan;17(1):1-8.
  12. Sareen S, Kumari V, Gajebasia KS, et al. Yoga: a tool for improving the quality of life in chronic pancreatitis. World J Gastroenterol 1-21-2007;13(3):391-397.
  13. Sharma VK, Das S, Mondal S, et al. Effect of Sahaj Yoga on depressive disorders. Indian J Physiol Pharmacol 2005 Oct-Dec;49(4):462-8.
  14. Streeter CC, Jensen JE, Perlmutter RM, et al. Yoga Asana sessions increase brain GABA levels: a pilot study. J Altern Complement Med 2007;13(4):419-426.
  15. Tekur P, Singphow C, Nagendra HR, et al. Effect of short-term intensive yoga program on pain, functional disability and spinal flexibility in chronic low back pain: a randomized control study. J Altern Complement Med. 2008 Jul;14(6):637-44.


British epidemiologist Archie Cochrane is regarded as the originator of the Evidence-Based Medicine concept (in the 1950s). And the Cochrane Library is a collection of very high-quality medical databases, which have, at their core, the Cochrane Reviews, systematic reviews and meta-analyses which summarize and interpret the results of well-conducted, randomized controlled trials… the ‘gold standard’ in Evidence-Based Medicine.

The Cochrane Library is a subscription-based database but offers free access to abstracts.


A service of the U.S. National Library of Medicine, PubMed was released in 1996 as a free digital archive of references and abstracts on life sciences and biomedical topics. PubMed comprises 20-million-plus citations for biomedical literature from MEDLINE, life science journals and online books from around the world. Some 11.5 million articles are listed with their abstract and 3.1 million articles are available in full-text for free.


The TRIP Database, launched in 1997, is a search engine designed to allow clinicians to quickly find answers to their medical questions using the best available evidence. Trip’s founders realized medical professionals were being forced to perform time-consuming searches at multiple websites to get at the most relevant information. So, they designed TRIP as a meta-search engine, allowing users to both simultaneously search thousands of databases, medical publications and resources, as well as easily filter the results: limiting searches to the most stringent, highest-quality medical evidence or expanding them to include results like patient information, news articles, etc.