It may be of interest to readers to note that the authors' comment about the use of the 28 item GHQ in reference 21 :
"A Rasch analysis of the GHQ-28 [21] has revealed a two factor structure based on positive and negatively worded items."
was actually a study of GHQ-30, not the GHQ28.
Competing interests
TJC (University of Cambridge) has worked as consulting psychometrician for GL Assessment (publisher of the GHQ) on an unrelated project (the standardization of the British Ability Scales-BAS3).
Wrong version cited
14 July 2015
It may be of interest to readers to note that the authors' comment about the use of the 28 item GHQ in reference 21 :
"A Rasch analysis of the GHQ-28 [21] has revealed a two factor structure based on positive and negatively worded items."
was actually a study of GHQ-30, not the GHQ28.
Competing interests
TJC (University of Cambridge) has worked as consulting psychometrician for GL Assessment (publisher of the GHQ) on an unrelated project (the standardization of the British Ability Scales-BAS3).