K10: Kessler Psychological Distress Scale, 10-item version

What this assessment is

The K10 measures nonspecific psychological distress over the past 30 days, or four weeks in some versions. Its 10 responses total either 0 to 40 or 10 to 50, depending on the coding system. Higher scores reflect more frequent distress. Reporting bands vary and do not diagnose a condition.

Ronald Kessler and colleagues developed the scale for population health surveys. The instrument developer describes the six-item K6 as a shorter form made from six of the K10 questions.

One total summarizes several forms of distress. It does not identify a condition or explain what caused the distress.

Who it was designed for

The K10 was developed for general population research. The developer documents its use in Australian and Canadian national health surveys and in the World Mental Health surveys.

The original development study tested the K10 in population surveys and a clinical reappraisal sample. Its purpose was efficient screening and population measurement, not diagnosis by questionnaire.

Before comparing results, check that the coding range, recall period, administration method, language version, and reference population are comparable.

How it is administered

The developer provides self-administered and interviewer-administered forms. The standard English forms ask about the past 30 days and use five frequency choices.

Australian surveys often say the previous four weeks. The 2020 to 2022 Australian national study used that wording and noted the difference from its earlier 30-day form.

Some K10+ forms add questions about persistence, functioning, healthcare use, and physical causes. Those extra questions do not contribute to the K10 total.

What it measures

The K10 measures broad distress in the anxiety and depression spectrum. It covers emotional and physical experiences associated with distress without assigning them to one diagnosis.

The total cannot identify why someone feels distressed. It also cannot show how much a specific problem affects work, relationships, self-care, or safety unless those topics are assessed separately.

How scoring works

The developer's scoring guide describes two coding systems that produce different totals from the same 10 responses:

• The developer's method assigns 0 to 4 points per response. The total runs from 0 to 40.
• The Australian method assigns 1 to 5 points per response. The total runs from 10 to 50.

A 10 to 50 total is exactly 10 points higher than the matching 0 to 40 total. Higher totals indicate more frequent psychological distress in both systems.

Always label the coding range. A total without that label can be misread because matching responses differ by 10 points across the two systems.

Missing responses also need a stated rule. The developer does not prescribe one method for every use. In the AIHW reporting method, all 10 responses are required before a total is calculated.

How to interpret a K10 score

There are no universal K10 severity bands. Even Australian government systems divide the 10 to 50 range in different ways.

The Australian Bureau of Statistics has used these groups:

• 10 to 15: low
• 16 to 21: moderate
• 22 to 29: high
• 30 to 50: very high

An Australian government metadata standard uses:

• 10 to 19: low
• 20 to 24: mild
• 25 to 29: moderate
• 30 to 50: severe

The Australian Institute of Health and Welfare warns that different groupings are used across surveys and research. These labels are reporting conventions tied to a method and population.

A K10 score is not a diagnosis. No band can confirm depression, an anxiety disorder, or serious mental illness. A clinical assessment is needed to determine whether a condition is present.

What the score cannot tell you

The total does not identify a cause or a specific disorder. It cannot decide whether someone needs medication, therapy, urgent care, or no care.

A low score does not rule out a condition. Symptoms can be controlled by treatment, fall outside the recall period, or appear in ways the K10 does not measure.

A high score supports a closer look at current symptoms and functioning, considered with the person's history, circumstances, and concerns.

Evidence and limitations

In the original development study, K10 scores discriminated between participants who met the study's structured diagnostic-interview case definition and those who did not. This does not make an individual score diagnostic.

One total combines several forms of distress and does not show which experiences drove the result.

Version details matter. A report should name the score range, timeframe, language, missing-response rule, and reference population before applying comparison bands.