Reconceptualising the factor structure of the Depression Anxiety Stress Scales (DASS) for traumatic brain injury
Alexia Samiotis1,2, Jai Carmichael1,2, Dana Wong3
1Monash-Epworth Rehabilitation Research Centre, Epworth HealthCare, Melbourne, Vic, Australia.
Objective:
We used contemporary factor analytic procedures to assess whether the Depression Anxiety Stress Scales (DASS) can reliably differentiate depression, anxiety and stress in individuals with traumatic brain injury.
Methods:
A total of 136 adults (Mage = 38.51 years; 77.94% male) with moderate-to-severe traumatic brain injury completed the DASS42. Various confirmatory factor models were estimated for both the DASS21 and DASS42, with a focus on novel statistical indices derived from bifactor modelling.
Results:
Bifactor modelling revealed a dominant general distress factor, accounting for 89% of the systematic variance in DASS21 total scores. Specific depression, anxiety and stress factors added little specific information when holding the general factor constant, accounting for only 11-27% of residual systematic variance in the subscale scores. Omitting the specific factors and instead treating the DASS21 as a unidimensional measure introduced minimal bias in parameter estimates. However, some multidimensionality was apparent when considering individual items, particularly from the depression scale. Additionally, first- and second-order factor models indicated that the specific factors were not well-differentiated from one another or from the general factor. These findings extended to the DASS42.
Conclusion:
In conclusion, scores on the DASS after traumatic brain injury predominately reflect a single underlying latent variable of general distress, providing support for using the total score over the three conventional scales.
