K10 (Kessler Psychological Distress Scale): Take It, Score It, Understand Your Results
The K10 (Kessler Psychological Distress Scale) is a brief self-report screening tool for non-specific psychological distress. Developed by Ronald Kessler and colleagues at Harvard Medical School and published in 2002, the K10 has been used in the WHO World Mental Health Surveys covering approximately 250,000 people across 30 countries. It asks 10 questions about how often you felt anxious, restless, hopeless, sad, or worthless over the past 4 weeks, each scored on a 5-point Likert scale from 1 (none of the time) to 5 (all of the time), giving a total in the 10-50 range. Two interpretation conventions coexist in the literature: the Andrews-Slade clinical bands used on patient-facing resources, and the Australian Bureau of Statistics statistical bands used in government population reporting. The K10 is a screening tool, not a diagnosis.
What is the K10?
The K10 (Kessler Psychological Distress Scale) is a brief 10-item self-report questionnaire developed by Ronald Kessler, Gavin Andrews, and colleagues, and published in 2002 in Psychological Medicine. The instrument was created with support from the US National Center for Health Statistics, originally for use in the redesigned National Health Interview Survey. The K10 sits inside a small family of related tools — the full 10-item K10 and its 6-item short form, the K6, share the same 1-to-5 response scale and the same underlying construct of non-specific psychological distress. The Harvard Medical School Kessler lab (hcp.med.harvard.edu/ncs/k6_scales.php) is the canonical developer-authority source for both scales. The K10 is widely used in primary care intake, epidemiological research, occupational health screening, and clinical-trial outcome monitoring, and has been adopted by national population health surveys in the United States, Australia, Canada, New Zealand, and by the WHO World Mental Health Survey program. It is one of the most widely deployed brief distress screeners worldwide.
What the K10 measures
The K10 measures non-specific psychological distress over the past 4 weeks. The 10 items ask about how often you felt tired without reason, nervous, restless or fidgety, hopeless, depressed, that everything was an effort, sad, or worthless during that window. The instrument was intentionally designed to be cross-cutting rather than syndrome-specific — the items overlap with both anxiety and depression symptoms, with the goal of detecting overall distress that warrants clinical attention without assuming the specific clinical picture in advance. Internal consistency is high: a 2024 reliability generalization meta-analysis pooling 48 studies and 236,259 participants found a Cronbach's alpha of 0.90 for the K10 across 26 studies, and pooled reliability held up across populations from adolescents to clinical outpatients. Confirmatory factor analysis supports a two-factor substructure (an anxiety facet and a depression facet) inside the broader non-specific distress construct, but the total score is treated as a single overall index.
How the K10 is administered
The K10 is a self-report questionnaire that takes about 5 minutes to complete. Each of the 10 items uses a 5-point response scale: None of the time (1), A little of the time (2), Some of the time (3), Most of the time (4), and All of the time (5). Each item asks about the past 4 weeks specifically. The total score is the simple sum of the 10 item responses, giving a range from 10 (minimum) to 50 (maximum). The K10 can be self-administered on paper, on a screen, or by interview, including by telephone. No fasting, special preparation, or clinician supervision is required, and the scale is free to use under a license that requires citing Kessler (2003) and including the World Health Organization copyright. Honest answers about the past 4 weeks are what give the score its meaning — the 4-week recall window is part of how the K10 distinguishes a tough patch from a persistent pattern of distress.
Who uses the K10
The K10 is used widely in mental health research, primary care, population health monitoring, and occupational health screening worldwide. It has been used in the WHO World Mental Health Surveys covering approximately 250,000 people across 30 countries, in the Australian National Survey of Mental Health and Wellbeing (where the ABS statistical bands originated), and in the Canadian National Health Interview Survey equivalent. New Zealand healthcare resources such as Healthify NZ deploy the Andrews-Slade clinical interpretation bands. Insurance, workplace, and occupational health programs in Australia and elsewhere include the K10 as a routine intake measure. The scale has been translated and validated in many languages, including Arabic, Chinese, Farsi, Indonesian, Japanese, Hindi, Portuguese, Swahili, Spanish, Korean, Thai, and Bengali. The K10 is also used routinely in clinical trials of mental-health interventions as a primary or secondary outcome measure for general psychological distress, and in epidemiological cohort studies tracking distress prevalence over time.
K10 is a screening tool, not a diagnosis
A K10 score signals how much psychological distress you experienced in the past 4 weeks and whether that warrants further clinical attention. It does not diagnose any specific condition (major depression, generalized anxiety disorder, or any other DSM-5 diagnosis) and cannot distinguish anxiety from depression or from somatic and medical drivers of similar symptoms. Healthify NZ states this directly: the K10 is indicative only and not intended to be a substitute for professional clinical advice, and only trained clinicians can provide formal diagnoses. The developers also note that symptom-screening scales like the K10 miss people who are successfully treated — a low score in someone on medication is not evidence the underlying condition has resolved. A high or persistent K10 score should prompt evaluation with a primary care clinician or mental health professional. If you are having thoughts of suicide or self-harm, call or text 988 (US Suicide and Crisis Lifeline) regardless of your K10 score.
How to score the K10: which convention applies to your number
A K10 total is the sum of your 10 item responses, each scored 1 (“none of the time”) to 5 (“all of the time”). That gives a total in the 10 to 50 range. The arithmetic is unambiguous. The interpretation is not. Two cutoff schemes coexist in the literature and on patient-facing resources, and the same raw score can fall in different bands depending on which one you read.
The two interpretation conventions
The first is the Andrews-Slade clinical convention (Australian and New Zealand researchers, 2001), reproduced by patient-facing resources such as Healthify NZ and NSW Health. The second is the Australian Bureau of Statistics (ABS) statistical convention, used inside Australian government population reporting.
| K10 score | Andrews-Slade clinical band | ABS statistical band |
|---|---|---|
| 10–15 | Likely to be well | Low distress |
| 16–19 | Likely to be well | Moderate distress |
| 20–21 | Mild distress | Moderate distress |
| 22–24 | Mild distress | High distress |
| 25–29 | Moderate distress | High distress |
| 30–50 | Severe distress | Very high distress |
A score of 22 reads as “mild” under the patient-facing convention and “high” under the ABS convention. Neither is wrong — they were derived for different purposes (clinical triage vs. population reporting). If your K10 result on another website gives a different label, this is almost always why.
License and access
The K10 is free to use; users are expected to cite Kessler and colleagues (2003) and include the WHO copyright. Screening, not diagnosis: regardless of band scheme, the number is a flag for further evaluation rather than a verdict.
How accurate is the K10? Reliability and validity across populations
The K10 has unusually strong psychometric backing for a 10-item self-report. Two questions to keep separate: reliability (do the items hang together?) and validity (does a high score correspond to a clinician-diagnosable disorder?). Different studies answer each.
Reliability: how internally consistent is the K10?
A 2024 reliability generalization meta-analysis pooled 48 studies and 236,259 participants across populations and geographic regions. The pooled internal-consistency estimates were:
- K10: Cronbach’s α = 0.90, 95% CI [0.88, 0.91] across 26 studies
- K6: Cronbach’s α = 0.84, 95% CI [0.80, 0.88] across 22 studies
- The K10 was significantly more reliable than the K6 (Cohen’s d = 0.77)
Reliability held up across populations: α = 0.93 in adolescents, α = 0.91 in carers, ranging from α = 0.85 (African samples) to α = 0.93 (combined North America and Australia samples). Arabic K10 validation in Palestinian social workers found α = 0.88, consistent with the meta-analytic estimate.
Validity: how well does the K10 identify clinical distress?
The strongest validity reference is the Kessler 2002 paper. Both scales were IRT-developed and validated against blinded SCID (DSM-IV) assessments. Discriminative performance was strong:
- Area under the ROC curve (AUC) of 0.87–0.88 for disorders with Global Assessment of Functioning (GAF) scores of 0–70
- AUC of 0.95–0.96 for disorders with GAF scores of 0–50 (more severe impairment)
- Standard errors of standardized scores of 0.20–0.25 in the 90th–99th percentile range — i.e., high precision exactly where clinical decisions are made
The original authors concluded that the K10 and K6 have “brevity, strong psychometric properties, and ability to discriminate DSM-IV cases from non-cases”. The K10 captures a single non-specific distress construct, with confirmatory factor analyses also supporting a two-factor substructure (anxiety facet and depression facet).
What the K10 does NOT tell you: non-specificity, treated cases, and the recall-window caveat
A K10 score is informative about how much distress you experienced in the past four weeks. Stretching the result past that is the most common interpretation error.
Limitations to keep in view
- It cannot name a specific disorder. The K10 measures non-specific distress and cannot distinguish anxiety from depression or from somatic and medical drivers of similar symptoms. A high score is consistent with several different clinical pictures, and the K10 alone cannot pick between them.
- It can miss people who are already in treatment. The developers note that symptom-screening scales “miss people who are successfully treated” — someone whose anxiety or depression is well-controlled on medication may score low even though the underlying condition is real.
- It cannot diagnose any mental health condition. Healthify NZ states this directly: “the K10 cannot diagnose mental health conditions — only trained clinicians can provide formal diagnoses”. The K10 is “indicative only” and is “not intended to be a substitute for professional clinical advice”.
- The 4-week recall window does not capture episodic patterns. The K10 asks about the past four weeks specifically. Cyclical mood patterns — periods of elevated mood or hypomania outside that month — fall outside what the K10 can see. Someone with episodic mood elevation can score low during a stable month with no signal that a clinician should also screen for mania history.
When other screeners belong in the picture
The K10 is a non-specific distress screen, not a bipolar spectrum screen. The MDQ (Mood Disorder Questionnaire) addresses a separate question (lifetime manic or hypomanic symptoms) that no K10 score, high or low, can rule in or out. This matters when someone has recurrent depressive episodes, periods of unusually elevated mood, decreased need for sleep, or treatment-resistant depression. Screening, not diagnosis: the K10 result is one input alongside the rest of the clinical picture, not a stand-alone verdict.
The K10 vs the K6 and other mental-health screeners
The K10 sits inside a small family of related tools. Knowing which one fits which question prevents the mistake of treating a single result as the whole answer.
K10 vs K6: the same construct, different lengths
The K6 is the K10 with four items removed. Both measure non-specific distress on the 1–5 scale and were validated together in Kessler 2002. The differences are practical:
| Feature | K10 | K6 |
|---|---|---|
| Items | 10 | 6 |
| Score range | 10–50 | 6 items on the same 1–5 scale |
| Major deployment | Australian and Canadian NHIS equivalents; WHO World Mental Health Surveys | US National Health Interview Survey (NHIS); National Survey on Drug Use and Health (NSDUH) |
| Standard cutoff | No single equivalent SMI cutoff; multiple band conventions in use | K6 ≥13 indicates likely serious mental illness (Kessler 2003) |
| Pooled reliability (2024 meta) | α = 0.90 | α = 0.84 |
The K6 ≥13 cutoff comes from Kessler et al. (2003) and is the threshold used in SAMHSA and NSDUH reporting. It applies to the K6 only — people sometimes import the “≥13” number to the K10, which is a misreading.
How the K10 compares to disorder-specific screens
The K10 is intentionally non-specific. Disorder-specific screens — the PHQ-9 (Patient Health Questionnaire-9) and the GAD-7 (Generalized Anxiety Disorder-7) — measure narrower constructs and grade severity within a single condition.
- Pick a K10 (or K6) when the question is overall distress regardless of syndrome — population health monitoring, primary-care triage, occupational health, or initial mental-health intake
- Pick a PHQ-9 when the question is depression severity specifically and how it changes over time
- Pick a GAD-7 when the question is anxiety severity specifically
The K10 has been used in the WHO World Mental Health Surveys covering approximately 250,000 people across 30 countries. None of these screeners diagnose anything. Screening, not diagnosis: they organize the conversation a clinician then has with you.
When to talk to a clinician (and what to do if you screen positive)
The K10 result on its own does not tell you what to do next. Score plus persistence plus impact on daily life is the combination that matters. The National Institute of Mental Health frames the same logic for anxiety: worry becomes clinical when it “does not go away, is felt in many situations, and can get worse over time.” It also becomes clinical when it “interferes with daily life and routine activities, such as job performance, schoolwork, and relationships”. The K10 operationalizes persistence by asking about the past four weeks; the impairment half is your own to weigh.
Consider scheduling an evaluation with a primary care clinician or mental health professional in any of these situations:
- Your K10 score is in the severe band (30 or higher) — Healthify NZ recommends seeing a doctor or mental health practitioner such as a counsellor, psychotherapist, or psychologist
- Your K10 score is moderate (25–29 clinical, 22–29 ABS) and the distress is interfering with work, school, relationships, or daily routines
- The pattern has lasted weeks rather than days — persistence separates a tough patch from a clinical concern
- You have noticed MedlinePlus warning signs — withdrawal from enjoyable activities, changes in eating or sleeping, persistent low energy, unexplained physical symptoms, or feeling helpless or hopeless
- You are pregnant, postpartum, in a college transition, or in the aftermath of trauma — recognized periods of heightened distress risk
If you are in crisis
If you are having thoughts of suicide or self-harm, or thoughts of harming others, call or text the 988 Suicide & Crisis Lifeline at 988. In a life-threatening situation, call 911. MedlinePlus lists “thoughts of self-harm or harming others” as a warning sign requiring immediate professional intervention regardless of any screening score. The 988 line offers phone, text, and chat services.
What an evaluation looks like
A clinician will take a history, ask about onset and triggers, screen for specific conditions, and rule out medical or substance-related contributors. Mental health conditions are treatable, and earlier evaluation widens the options. Categories may include talk therapy, medication, or a combination — specifics belong to the clinician.
Frequently asked questions
What is the difference between the K10 and the K6?
The K6 is the K10 with four items removed. Both measure non-specific distress on a 1–5 scale; the K10 runs 10–50. The K6 has a standard ≥13 cutoff for likely SMI (Kessler 2003) used by SAMHSA and NSDUH; the K10 does not have a single equivalent SMI cutoff.
Where can I get the official K10 PDF?
The K10 is free to use and does not require formal permission. The developer-authority page is the Kessler lab at Harvard Medical School (hcp.med.harvard.edu/ncs/k6_scales.php), the canonical source for licensing and the K6 PDF. The McGill MAP-PRO measures library is a second-source authority confirming the same licensing terms.
Why do I see “0–40” instead of “10–50” on some K10 PDFs?
Some K10 versions score items 0–4 rather than 1–5, which shifts the total to 0–40. The ABS National Health Survey convention used here is 1–5 scoring with a 10–50 total. If your form sums to 0–40, check the response anchors before applying a cutoff band.
Which cutoff is correct, ABS or Andrews-Slade?
Both are correct for their purposes. Andrews-Slade clinical bands (10–19 likely well / 20–24 mild / 25–29 moderate / 30–50 severe) are used by patient-facing resources such as Healthify NZ. ABS statistical bands (10–15 / 16–21 / 22–29 / 30–50) are used in Australian population reporting. The same raw score can fall in different bands depending on the scheme.
Is the K10 just a depression test?
No. The K10 is a non-specific distress screen — items overlap with anxiety, depression, and general distress without targeting any single syndrome. Confirmatory factor analysis supports a two-factor substructure (anxiety + depression facets) inside the broader non-specific construct.
What should I do if I score 30 or higher?
A K10 score in the severe band warrants a clinician evaluation. A 30+ score with persistent distress over several weeks is the pattern that benefits from a primary care or mental health appointment. If you are having thoughts of suicide or self-harm, call or text 988 (US Suicide & Crisis Lifeline) regardless of your score.
Can a low K10 score rule out a mental health condition?
No. The developers note that symptom-screening scales “miss people who are successfully treated” — a person whose condition is medication-controlled may score low even though the diagnosis is real. The K10 also reflects only the past four weeks, so episodic patterns outside that window can be missed.