Validity and Reliability of the Filipino Version of the Kessler Psychological Distress Scale

Kessler Psychological Distress Scale (K6) is a self-administered and short screening instrument for non-specific psychological distress and is used internationally in epidemiological studies because of its good psychometric properties. K6 can be feasibly used to screen for mental health problems in settings with limited mental health professionals, such as in low- and middle-income countries. This study aims to examine the psychometric validity, construct validity, and internal consistency of the Filipino version of K6.

The participants were recruited from the community in Muntinlupa City, Philippines, and from patients in a psychiatric unit run by the local government in Muntinlupa. A structured questionnaire was used to collect data from both groups. The questionnaire assessed sociodemographic characteristics and included the K6 scale. For outpatients, in addition to the items used for community members, Patient Health Questionnaire-9 (PHQ-9), World Health Organization-Five Well-Being Index (WHO-5), and World Health Organization Quality of Life - BREF (WHOQOL-BREF) were employed to examine construct validity. Depression severity and diagnosis were determined by a psychiatrist or a resident doctor based on an unstructured clinical interview with three options: mild, moderate, and severe, and diagnostic criteria, respectively. Internal consistency and psychometric validity were assessed using Cronbach's α and an unpaired t-test for the total K6 score between patients assessed as having mild depression and those with moderate or severe depression, respectively. K6 scores of community people and patients from the psychiatric unit were compared using a Mann-Whitney U test.

In total, 95 people from the psychiatric unit (27 male patients, 77 female patients, and one gender-diverse) and 405 people from the community (178 male participants, 226 female participants, and one gender-diverse) participated in the study. Cronbach's α of K6 was 0.88. Patients in the psychiatric unit had higher K6 total scores (median 14.00) than the participants from the community (median 3.00). Coefficient correlation analysis showed that K6 was strongly and positively correlated with PHQ-9 (r = 0.74, p < 0.01) and moderately and negatively correlated with WHO-5 (r = -0.51, p <0.01) and Psychosocial health in WHOQOL-BREF (r = -0.59, p < 0.01). The optimal cutoff points for moderate and serious psychological distress were 6/7 and 11/12, respectively, based on the distribution of scores. Patients assessed as having moderate or severe depression had a statistically higher K6 score (Mean 15.60) than those assessed as having mild depression (Mean 12.96).

The Filipino version of K6 is appropriate for measuring psychological distress in clinical and community settings. The Filipino version of K6, including cutoff points, will be a useful tool in the local context in practice and can be used as a measurement tool in studies to promote mental health in various settings.