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The Kessler Psychological Distress Scale (K-10) is a ten-item self-report questionnaire designed to measure non-specific psychological distress over the preceding four weeks. Developed by Professor Ronald Kessler and colleagues at Harvard Medical School, the K-10 was designed for use in population health surveys and has become one of the most widely used distress measures in Australian healthcare.

Each item is scored from 1 ("None of the time") to 5 ("All of the time"), producing a total score between 10 and 50. Higher scores indicate greater psychological distress. The K-10 does not measure a specific disorder but rather captures a broad dimension of psychological distress that is associated with anxiety and depressive disorders.

The K-10 was developed using item response theory (IRT) methods, drawn from a large pool of screening questions tested across multiple population surveys. The final 10 items were selected based on their ability to discriminate across the full range of psychological distress severity, with particular precision at the severe end of the distribution.

The original development study, published in 2002, demonstrated excellent psychometric properties. The K-10 showed strong unidimensionality, high internal consistency, and robust discrimination between community cases and non-cases of DSM-IV anxiety and mood disorders.

A key strength of the K-10 is its design for population-level screening. Unlike instruments developed in clinical samples, the K-10 was calibrated to detect distress across the full spectrum — from well individuals to those with severe mental illness. This makes it particularly useful for epidemiological research and public health monitoring.

The K-10 uses a five-point response scale for each of its ten items:

1 = None of the time 2 = A little of the time 3 = Some of the time 4 = Most of the time 5 = All of the time

Total scores range from 10 to 50 (note: the minimum is 10, not 0, because the lowest possible response per item is 1). Published severity thresholds commonly used in Australian settings are:

10–19: Low distress 20–24: Mild distress 25–29: Moderate distress 30–50: High distress — clinical follow-up recommended

The four-week timeframe gives a broader picture of distress compared to two-week measures like the PHQ-9 and GAD-7, making it less sensitive to daily fluctuations.

The K-10 serves as a general psychological distress measure, capturing symptoms common to both anxiety and depressive disorders. This makes it useful as a broad screening tool when the clinical picture is unclear, or when a general measure of mental health is preferred over disorder-specific instruments.

In clinical settings, the K-10 is used for intake screening, treatment monitoring, and outcome evaluation. Its sensitivity at the severe end of the distress spectrum makes it particularly valuable for identifying individuals who may need urgent attention.

The K-10 is also used extensively in workplace mental health programs, employee assistance programs, and community health settings. Its non-specific nature means it captures distress regardless of its specific diagnostic source.

The K-10 holds a unique position in Australian healthcare. It is the standard psychological distress measure used in the Australian Bureau of Statistics National Health Survey and the National Survey of Mental Health and Wellbeing. This means Australian population norms are readily available for comparison.

Under Medicare's Better Access initiative, the K-10 is one of the recommended outcome measures for mental health treatment. It is widely used by GPs, psychologists, psychiatrists, social workers, and other practitioners providing services under the program.

The K-10 is also used in Primary Health Network-commissioned mental health services (formerly the ATAPS program) and headspace centres. Its adoption across Australian healthcare systems means that K-10 scores can facilitate communication between providers and support continuity of care.

Culturally adapted versions of the K-10 have been developed for use with Aboriginal and Torres Strait Islander communities, supporting appropriate assessment across diverse populations.