Monday August 23 2010
People who wish to try yoga may find that it is of some help
“Yoga protects the brain from depression,” The Daily Telegraph reported. It said that researchers have found that three sessions of yoga a week can help to keep you relaxed and prevent depression.
This small trial randomly allocated 52 healthy people to either yoga or a walking exercise for 12 weeks. Assessments of the participants’ psychological state were made before and after this time, as were brain scans to look at their levels of GABA, a chemical that transmits messages in the brain and plays a role in mood and anxiety.
This study’s findings should be interpreted with caution. Only 34 participants (65%) completed the study, meaning it has “low power” and brings the reliability of its findings into question. Importantly, none of these people had psychological disorders or were assessed for these after the trial. As such, the study alone cannot prove that yoga can treat or prevent depression or any other mood disorder. The findings need to be confirmed in larger and more varied groups of people.
Despite the study’s limitations, physical activity is known to have many benefits, including a positive effect on mood. People who wish to try yoga may find that it is of some help.
Where did the story come from?
The study was carried out by researchers from the University School of Medicine in Boston, and other institutions in the USA. It was funded by grants from the National Institute of Health. The study was published in the peer-reviewed Journal of Alternative and Complementary Medicine.
This was a study in healthy people, so The Daily Telegraph’s report that three sessions of yoga a week “fight off depression” is inaccurate. The newspaper has also not recognised the limitations of this small study, which had a high drop-out rate.
What kind of research was this?
This small randomised controlled trial compared yoga to a walking exercise for their effects on mood, anxiety and levels of the brain chemical GABA in healthy people. GABA is a chemical that transmits messages between nerve cells in the brain. People with psychological disorders often have reduced levels of it. Yoga is thought to have beneficial effects on mood, and the researchers wanted to see whether any observed effects were specific to yoga, or just related to physical activity in general.
What did the research involve?
The researchers recruited healthy subjects aged between 18 and 45 who had no medical or psychiatric illnesses. They excluded people who had done any yoga in the past three months, or had ever performed yoga on a weekly basis for more than four weeks. They discounted those who currently took part in psychotherapy, prayer groups, or any mind–body disciplines. People who had taken medications that might affect the GABA system within the past three months were also discounted, as were users of tobacco products. Anyone who drank more than four alcoholic drinks a day was also excluded, as were those with contraindications to brain scans.
The researchers randomly allocated 28 people to yoga and 24 to a walking exercise. Both groups were asked to do either exercise (under the guidance of trained professionals) for 60 minutes, three times a week for 12 weeks. The yoga and walking exercise programmes were matched to ensure they both required the same level of energy input.
An initial brain scan to measure GABA levels was taken at the start of the study, followed up by another scan after the treatment period had finished 12 weeks later. Immediately following the second scan, participants took part in a final 60-minute yoga or walking session, after which a third scan was performed to see the immediate effects of exercise on GABA levels. Various assessments of mood and anxiety were made at the start of the study and then repeated at weeks 4, 8 and 12, and before each brain scan. The researchers assessed anxiety using the State scale of the Spielberger State–Trait Anxiety Inventory (STAI-State), and mood using the Exercise-Induced Feeling Inventory (EIFI). The EIGI is made up of four subscales, three of them relating to "positive" mood (positive engagement, revitalization, and tranquility) and one relating to "negative" mood (physical exhaustion).
What were the basic results?
Of the 52 people randomised in the study, only 34 (65%) completed the study and were included in the analysis. On average, people in both groups attended two-thirds of the 36 sessions. Within the yoga group, their score on the STAI-State scale after the 12 weeks of yoga sessions showed that anxiety levels had lowered. Between-group analyses showed the yoga groups’ anxiety levels had lowered more than the walking groups had. Scores on the EIFI after 12 weeks also demonstrated that the yoga group had improved their mood relative to the walking group by scoring higher on the three "positive" subscales and lower on the "negative" subscale.
Improved mood and decreased anxiety were also associated with increased GABA levels on the brain scans. Again, these positive correlations were noted in the yoga group.
How did the researchers interpret the results?
The researchers conclude that the 12-week yoga intervention was associated with greater improvements in mood and anxiety than a metabolically matched walking exercise.
They say that theirs is also the first study to demonstrate that increased GABA levels in the brain are associated with improved mood and decreased anxiety. They say that “the possible role of GABA in mediating the beneficial effects of yoga on mood and anxiety warrants further study”.
This study has a number of limitations, which affect the reliability of the conclusions that can be drawn:
- The trial was small to begin with, randomising only 52 people. Only 65% then completed the study and were analysed, which gives the study low power to detect any differences between the groups reliably. The small number of participants also means that the randomisation may not have been able to balance the groups sufficiently for all factors that could have affected the results. Therefore, any differences between the groups must be interpreted with caution.
- None of the participants had psychological disorders, so the researchers cannot conclude that yoga is beneficial for treating depression or any other mood disorder. The study also did not assess whether the treatments prevented these healthy individuals from developing psychological disorders, therefore it cannot tell us whether “yoga protects the brain from depression”, as suggested by The Telegraph.
- As the scales the study used to assess mood did not use any of the more commonly used measures for assessing symptoms of depression, making it difficult to determine the effect of the interventions on such symptoms.
The findings may be worth further study in larger and more varied groups of people to see whether yoga does have specific benefits compared to other types of exercise. In general, physical activity is considered to have many benefits, including a positive effect on mood.