The results of 20 trials suggest that music listening may have a
beneficial effect on anxiety in people awaiting surgery. Music listening
resulted, on average, in an anxiety reduction that was 5.72
units greater than that of the standard care group, as measured by
the STAI-S. At this time, there is no consensus on what constitutes
a clinically significant change in anxiety as measured by the STAIS.
However, assessment of clinical significance is often determined
using 0.5 standard deviation (SD) of the baseline measure as a
guideline (Sloan 2005). Baseline SDs of studies included in this review
ranged from 5.7 to 10.66, with a mean SD of 8.77. Based on
the 0.5 SD rule, the difference between the treatment group and
control group found in this review could therefore be considered
clinically significant. Studies that used anxiety scales other than
the STAI-S resulted in a difference of -0.60 standardized units. Although
the magnitude of the effect differed across the studies that
used non-STAI anxiety scales, the trials agreed on the direction of
the point estimates. These anxiety-reducing results are considered
moderate in size according to interpretation guidelines put forth
by Cohen (Cohen 1988). Cohen suggested that an effect size of
0.2 be considered a small effect, an effect size of 0.5 medium, and
an effect size of 0.8 large.