Three hundred and thirty six college
students (m=107, f= 229) between the ages of 18 and 25 (mean age = 20.18, sd=1.97)
completed online Type D, ISI, DBAS, SHI and caffeine consumption. Breakdown for
Insomnia Severity Index, 1=55.9%, 2=32.8%, 3=10.1%, 4=1.2%. There was a positive bivariate relationship
between scores on the Insomnia Severity Index and Type D interaction term
scores, r = 0.276, n=338, p < .0005. Type
D was also highly correlated with DBAS and SHI, there was no significant
relationship with caffeine consumption. However, when DBAS, and SHI scores were
entered into a multiple regression model Type D was no longer predictive. With ISI as the dependent variable, the model
explained 36% of the variance, F(3,334) =62.837, p<.0005. In this model DBAS
and SHI were independent predictors (p<.0005), while Type D failed to
contribute, thus indicating that the relationship between Type D and insomnia
is mediated by DBAS and SHI.