Psychometric evaluation of the patient health questionnaire stress scale

The "Patient Health Questionnaire (PHQ)" is a screening instrument, designed for time-efficient detection and severity assessment of depression, anxiety, and other syndromes in medical settings. Besides the questions on psychological symptoms, there are items on psychosocial functioning, on stressors and critical life events. However, for the stress items there are no psychometric properties available until now. The present study is thought to investigate item characteristics, internal consistency as well as factorial and construct validity of the stress scale of the PHQ. A representative sample of the general population of Germany was collected by a demography consulting company (USUMA, Berlin). Per random-route procedure, households and members of the households were selected. The sample was representative for the German community regarding age, gender, and education. In this investigation the following questionnaires were administered: PHQ-Stress, Questions on Life Satisfaction Modules (FLZ-M), Type-D Scale-14 (DS14). The sample included N = 2396 participants with mean age of 48.50 (SD = 17.75; range = 14 to 92) and 55.2 % being female. Reliability of the PHQ stress scale was acceptable (ω = 0.776), but some factor loadings were comparatively low. Model fit indices showed mixed results, some indicating unacceptable and some indicating acceptable fit of the 10-item stress scale of the PHQ. Correlations with related constructs demonstrated the scale's convergent validity. The results of this validation study indicate that the PHQ stress scale, which provides a one-dimensional total stress score, is a valid, good practical and reliable self-report instrument for assessing the severity of psychosocial stress.