Abstract: We included only one small trial published as an abstract article. The included study investigated the effects of meditation practice on patients newly hospitalised with acute leukaemia. Ninety-one participants enrolled in the study, but only 42 participants remained in the trial throughout the six-month follow-up period and were eligible for analysis. There was no information provided about the average age and sex of the study population. We found a high risk for attrition bias and unclear risk for reporting bias, performance and detection bias because of missing data due to abstract publication only, thus we judged the overall risk of bias as high. According to the GRADE criteria, we judged the overall quality of the body of evidence for all predefined outcomes as 'very low', due to the extent of missing data on the study population, and the small sample size. As the abstract publication did not provide numbers and results except P values, we are not able to give more details. Meditation practice might be beneficial for the quality of life of haematologically-diseased patients, with higher scores for participants in the mediation arms compared to the participants in the usual care control group (low quality of evidence). Levels of depression decreased for those practising meditation in both the spiritually-framed meditation group and the secularly-focused meditation group in comparison to the usual care control group, whose levels of depression remained constant (low quality of evidence). The influence of meditation practice on overall survival, fatigue, anxiety, quality of sleep and adverse events remained unclear, as these outcomes were not evaluated in the included trial. To estimate the effects of meditation practice for patients suffering from haematological malignancies, more high quality randomised controlled trials are needed. At present there is not enough information available on the effects of meditation in haematologically-diseased patients to draw any conclusion.

Plain-language summary: We included one trial with 91 adult patients, of whom only 42 were analysed. The trial involved five one-hour meditation intervention sessions between admission and discharge of participants newly diagnosed with acute myeloid or lymphoid leukaemia. There was no information about the age of the participants included in the study. All participants in the trial were hospitalised for initial induction chemotherapy. As the abstract of the publication did not provide numbers, it is not possible to describe the results in more detail. Participants practising meditation reported better physical health and levels of depression could be decreased. Most of our pre-defined outcomes (overall survival, anxiety, fatigue, quality of sleep, and adverse events) were not reported at all. We judge the quality of the evidence for the outcomes quality of life and depression as 'very low', due to high risk of bias (only 42 out 91 participants were evaluated) and very imprecise results. There were not enough data available to determine the effectiveness of meditation practice on haematologically-diseased patients, thus the role of meditation in the treatment of haematological malignancies remains unclear. More high-quality and larger randomised controlled trials are needed to validate possible positive effects of meditation practice for haematologically-diseased patients. The evidence is up-to-date as of August, 2015.