Abstract: Our search strategies led to 149 potentially relevant references, but only a single small study met our inclusion criteria. The included study was published as a full text article and investigated the feasibility and effect of Tibetan Yoga additional to standard care (N = 20; 1 person dropped out before attending any classes and no data were collected) compared to standard care only (N = 19). The study included people with all stages of Hodgkin and non-Hodgkin's lymphoma, with and without current cancer treatment. The mean age was 51 years. We judged the overall risk of bias as high as we found a high risk for performance, detection and attrition bias. Additionally, potential outcome reporting bias could not be completely ruled out. Following the recommendations of GRADE, we judged the overall quality of the body of evidence for all predefined outcomes as 'very low', due to the methodical limitations and the very small sample size. The influence of yoga on HRQoL and OS was not reported. There is no evidence that yoga in addition to standard care compared with standard care only can improve distress in people with haematological malignancies (mean difference (MD) -0.30, 95% confidence interval (CI) -5.55 to 4.95; P = 0.91). Similarly, there is no evidence of a difference between either group for fatigue (MD 0.00, 95% CI -0.94 to 0.94; P = 1.00), anxiety (MD 0.30, 95% CI -5.01 to 5.61; P = 0.91) or depression (MD -0.70, 95% CI -3.21 to 1.81; P = 0.58). There is very low quality evidence that yoga improves the overall quality of sleep (MD -2.30, 95% CI -3.78 to -0.82; P = 0.002). The yoga groups' total score for the Pittsburgh Sleep Quality Index (PSQI) was 5.8 (± 2.3 SD) and better than the total score (8.1 (± 2.4 SD)) of the control group. A PSQI total score of 0 to 5 indicates good sleep whereas PSQI total score 6 to 21 points towards significant sleep disturbances. The occurrence of AEs was not reported. The currently available data provide little information about the effectiveness of yoga interventions for people suffering from haematological malignancies. The finding that yoga may be beneficial for the patients' quality of sleep is based on a very small body of evidence. Therefore, the role of yoga as an additional therapy for haematological malignancies remains unclear. Further high-quality randomised controlled trials with larger numbers of participants are needed to make a definitive statement.

Plain-language summary: We included a single trial with 39 participants in the review (20 in the yoga group and 19 in the control group). The trial looked at a seven-week Tibetan Yoga program in a group of people with Hodgkin and non-Hodgkin's lymphoma. The average age was 51 years. The trial involved patients who were currently receiving anti-cancer therapy as well as patients who were not receiving active therapy. The trial found insufficient data to make a judgement about the efficacy of yoga on distress, fatigue, depression and anxiety compared with patients not practicing yoga. Yoga can improve the patients' quality of sleep. The trial gave no information about health-related quality of life, overall survival or adverse events. On the basis of the GRADE criteria, we judged the overall quality of evidence for yoga concerning the outcomes distress, fatigue, anxiety, depression and quality of sleep as 'very low'. There are not enough data to say how effective yoga is in the management of haematological malignancies. Therefore, the role of yoga for haematological malignancies remains unclear. Further large, high-quality randomised controlled trials are needed. The evidence is up-to-date as of 4 February 2014.