In the outpatient study , subjective sleep onset latency after middle-of-the-night was significantly shorter for both genders treated with ZST 3.5 mg versus placebo over the 4-week average ( females : 37.3 vs. 59.4 min , p < 0.0001 ; males : 38.6 vs. 55.1 min , p0 .01 ) .