Placebo is effective to treat insomnia?

In clinical trial, sometime we may found placebo administration significantly decreased subjective sleep latency and increased subjective total sleep time. So is placebo effective to treat insomnia?

Recently, Ogawa et al from Kyoto University in Japan investigate the association between subjective sleep latency  fluctuation and the placebo response. They found higher fluctuation of subjective sleep latency was associated with a greater decrease in subjective sleep latency in placebo treatment. Multivariate analysis suggested that a wider standard deviation for daily subjective sleep latency and a higher weekly mean sSL were independent predictors of greater improvement in mean subjective sleep latency during the subsequent weeks of placebo treatment. Likewise, a wider standard deviation and lower mean of subjective total sleep time were independent predictors of greater improvement in mean subjective total sleep time  in the subsequent weeks.

So, placebo is effective to treat the insomniac with high fluctuation of subjective sleep latency and total sleep time.