The study investigated the human leucocyte antigen (HLA), types A, B and DR, of 
42 patients with delayed sleep phase syndrome (DSPS) and compared the 
frequencies of the antigens with those in 117 healthy controls. The comparison 
revealed that the gene frequencies and positivities of HLA-A, -B and -DR, except 
for DR1, had no significant differences between the patients and controls. The 
frequency of HLA-DR1 was increased in the DSPS patients as compared with that in 
the healthy controls (P = 0.0069 in positivity). Although the corrected P-value 
(0.069) for multiple comparisons almost reached the significance level, the 
results indicated a possible association of the HLA-DR1 antigen with DSPS. This 
study suggests that there are genetic predispositions to DSPS.