General health questionnaire--12 items: adaptation study to the Portuguese population

To assess the validity and reliability of the GHQ-12 in Portugal.

Using a standard 'forward-backward' translation procedure, the English language version of the questionnaire was translated into Portuguese. To test reliability the internal consistency was assessed by Cronbach's alpha coefficient. Validity was performed using convergent validity. Finally, the factor structure of the questionnaire was extracted by performing principal component analysis using varimax rotation.

In all 790 undergraduates entered into the study. Reliability analysis showed satisfactory result (Cronbach's alpha coefficient = 0.91). Convergent validity indicated a significant negative correlation between the GHQ-12 and social support scores as expected (r = -0.54, P < 0.001). The principal component analysis showed that the GHQ-12 was a measure with two-factor structure.

The Portuguese version of the GHQ-12 has a good structural characteristic for measuring psychological well being.