DBH and myalgic encephalomeyelitis/chronic fatigue syndrome: For both genotypes, CFS increased the arousal index (Dbh+, t = 7.9; p < 0.001 and Dbh−, t = 8.4; p < 0.001), so that in response to CFS, the arousal index was similar for CFS Dbh+ and Dbh− mice (t = 2.0, N.S.), as summarized in Figure 1B.