Data synthesis
We understand that there is no closed argument for preference for
use of fixed-effect or random-effects models. The random-effects
method incorporates an assumption that the different studies are
estimating different, yet related, intervention effects. This often
seems to be true to us and the random-effects model takes into
account differences between studies even if there is no statistically
significant heterogeneity. There is, however, a disadvantage to the
random-effects model. It puts added weight onto small studies
which often are the most biased ones. Depending on the direction
of effect, these studies can either inflate or deflate the effect size. We
chose fixed-effect model for all analyses. The reader is, however,
able to choose to inspect the data using the random-effects model.
Subgroup analysis and investigation of heterogeneity
1. Subgroups
We anticipated no subgroup analyses.
2. Investigation of heterogeneity
If we found heterogeneity (see under Assessmentof heterogeneity),
we examined the following possible sources of heterogeneity:
• treatment ’dosage’ (20 sessions or more versus less than 20
sessions); and
• treatment approach (quality of music therapy method and
training).
Sensitivity analysis
We planned to investigate the effect of including studies with high
attrition rates on the primary outcomes, but no such studies were
identifiedinthisreview. We didhowever, compare the results when
we included our assumptions regarding those lost to follow-up (see
Dealing with missing data) with ’completer only’ analyses.
R E S U L T S
Description of studies
See: Characteristicsof includedstudies; Characteristicsof excluded
studies; Characteristics of ongoing studies.
Results of the search
The original search identified 34 potentially relevant studies (Gold
2005a). Updated searches in 2008 and 2010 yielded 97 references
(from 81 studies), and 18 references (from 18 studies), respectively. After excluding duplicates and clearly irrelevant references,
we inspected 85 studies closely for possible inclusion. We include