Is the total DASS score a useful measure?
Yes it is certainly both possible and sensible to add (or average) the three DASS scores together to produce a composite measure of negative emotional symptoms. If you have access to the DASS manual (see FAQ4), the best way to do this while retaining a connection to the normative data is to first convert each scale score to a Z score (i.e., subtract mean and divide by SD from the normative data for that scale) and then average the Z scores. Then you can compare the average Z score for an individual or group to the severity labels in the same way as for individual scales.
