Correlations utilizing the factors revealed a strong positive
relationship between the cognitive–emotional factor and the DASS
depression scale, and positive but weaker correlations between
the lethargy and academic motivation factors and the DASS
depression scale. This indicates that the USDI cognitive–emotional
factor represents a construct more similar to the DASS depression
items than the academic motivation or lethargy factors. This
finding is consistent with the theoretical development of the USDI
that reported the cognitive–emotional factor contains items
reflecting symptoms of depression commonly found in the general
population, rather than specifically the student population as is
the case with items in the academic motivation factor (Khawaja
and Bryden, 2006). Finally, the USDI was strongly negatively
correlated with the LSS-subjective state, indicating that as
reported levels of depression increased on the USDI, the reported
level of life satisfaction decreased on the LSS, which is consistent
with previous research into depression and satisfaction with life
(Simpson et al., 1996). This evidence suggests that the USDI has
sound concurrent and discriminant validity.
4.3. Severity categories of the USDI
An additional purpose of this study was to create severity
categories to aid interpretation of scores on the USDI in individual
applications. The lack of interpretation guidelines restricts the
clinical utility of the USDI, as total scores provide limited conceptual
meaning regarding test responders’ severity of depressive
symptoms. As the distribution of the data was considered normal,
z scores were used to determine cut-off scores for correspondinginterpretive labels. This resulted in the creation of four severity
categories; ‘low’ (which reflects USDI scores at and below the
mean of the standardization sample) ‘moderate’ (which reflects
USDI scores one standard deviation above the standardization
sample mean), ‘high’ (which reflects USDI scores two standard
deviations above the standardization sample mean) and ‘very
high’ (which reflects USDI scores three standard deviation above
the standardization sample mean). The categories aim to enable a
clinician to conceptualize the meaning of a test taker's total score
in terms of where it falls in comparison to the standardization
sample. The current study also employed other well validated
scales of depression and life satisfaction as a reference to evaluate
the resulting severity categories and verify them as practical as
well as theoretically meaningful.