Patient health Questionnaire-9 in spinal cord injury: an examination of factor structure as related to gender.
OBJECTIVE
Despite the attention depression after spinal cord injury (SCI) has received, research and clinical practice have been hampered by inadequate emphasis on reliable and valid measurement. Assessment of symptoms in persons with SCI is challenged by the presence of "trans-diagnostic" symptoms and unexamined effects of gender. The objective of this study was to examine the factor structure of the Patient Health Questionnaire-9 (PHQ-9; the 9-item depression scale of the Patient Health Questionnaire) and determine whether the structure replicates across gender.


METHODS
A total of 1,168 women and men were matched on level/completeness of SCI, follow-up year, and age to create 584 pairs. Exploratory factor analysis examined 1- and 2-factor models and congruence in 2 randomly split half samples to establish congruence of the factor solution and replication across gender.


RESULTS
The 1- and 2-factor solutions fit the structure of the items accounting for 41% to 51% of original item variance. Congruence between random samples was uniformly high for the 1-factor solution (r = 0.791-0.948) but variable for the 2-factor solution. Although congruence was high for the combined sample and men (r = 0.90-0.97 and 0.71-0.94, respectively), it was variable for women (r = 0.29-0.85).


CONCLUSIONS
Although there was support for the 1-factor structure of the PHQ within and between sexes, the low congruence between sexes and within women for the 2-factor structure indicates potentially important differences about how certain symptoms may be experienced or interpreted differently, by men and women with SCI. Future research should focus on where sexes diverge in cognitive, affective, and somatic dimensions of depressive symptoms and whether sex-specific or sex-neutral measures are warranted.
Kalpakjian
Claire Z
CZ
Model SCI System, Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor 48109, USA. clairez@umich.edu
Toussaint
Loren L
LL
Albright
Kathie J
KJ
Bombardier
Charles H
CH
Krause
James K
JK
Tate
Denise G
DG
D003863:Depression / Q000175:diagnosis* / Q000209:etiology*; D005163:Factor Analysis, Statistical; D005260:Female; D005500:Follow-Up Studies; D006304:Health Status; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D012727:Sex Characteristics; D013119:Spinal Cord Injuries / Q000150:complications / Q000175:diagnosis / Q000523:psychology; D011795:Surveys and Questionnaires