How is the PHQ-9 scored?

9 items scored 0–3 (not at all, several days, more than half the days, nearly every day). Total 0–27. Scores: 1–4 minimal; 5–9 mild; 10–14 moderate; 15–19 moderately severe; 20–27 severe.

What PHQ-9 score suggests MDD?

Score ≥10 has sensitivity 88% and specificity 88% for major depressive disorder. Score ≥15 indicates moderate–severe MDD requiring urgent treatment.

What does item 9 of the PHQ-9 assess?

Item 9 screens for suicidal ideation: 'thoughts that you would be better off dead or of hurting yourself.' Any score >0 requires direct clinical assessment.

PHQ-9 Depression Screening Calculator

Constant	Symbol	Value	Units
Speed of light	c	2.99792458×10⁸	m/s
Planck's constant	h	6.62607015×10⁻³‴	J·s
Boltzmann constant	kʙ	1.380649×10⁻²³	J/K
Avogadro's number	Nₐ	6.02214076×10²³	mol⁻¹
Gravitational constant	G	6.6743×10⁻¹¹	N·m²/kg²
Gas constant	R	8.31446	J/(mol·K)
Elementary charge	e	1.602176634×10⁻¹⁹	C
Electron mass	mₑ	9.1093837015×10⁻³¹	kg
Proton mass	mₚ	1.67262192369×10⁻²⁷	kg
Fine-structure constant	α	7.2973525693×10⁻³	dimensionless

Constant

Symbol

Value

Speed of light

2.99792458×10⁸

Planck's constant

6.62607015×10⁻³‴

Boltzmann constant

kʙ

1.380649×10⁻²³

Avogadro's number

Nₐ

6.02214076×10²³

Gravitational constant

6.6743×10⁻¹¹

Gas constant

8.31446

Elementary charge

1.602176634×10⁻¹⁹

Electron mass

mₑ

9.1093837015×10⁻³¹

Proton mass

mₚ

1.67262192369×10⁻²⁷

Fine-structure constant

7.2973525693×10⁻³

Formula Definitions

The PHQ-9 Depression Screening Calculator works by applying a well-defined formula to the values you enter. Understanding the formula behind the calculation helps you interpret the result and check that your inputs are correct. Below we break down the key components that drive the PHQ-9.

The core formula used by this calculator is:

Result = f(patient inputs, clinical reference)

Each variable in the formula has a specific meaning:

patient inputs — Age, weight, height, lab values, vitals, or clinical findings entered into the PHQ-9.
clinical reference — Reference range, scoring system, or population standard the result is compared against.
Result — Computed clinical score, risk estimate, or diagnostic value.

Note: Clinical results are decision-support only and must be interpreted by a qualified clinician.

How to Use This Calculator

Enter patient clinical data. Enter the patient's age, weight, lab values, vitals, or clinical findings into the PHQ-9 Depression Screening Calculator input fields.

Select the clinical scoring system. Select or confirm the appropriate clinical scoring system or reference range for the patient population.

Calculate the clinical score. Press Calculate to compute the clinical score, risk estimate, or diagnostic result.

Interpret the result. Review the output against the provided reference ranges, risk categories, or guideline thresholds. Consult a qualified clinician before acting on results.

Glossary and Definitions

Clinical score

A numeric value derived from patient inputs that estimates risk, severity, or diagnostic likelihood for a given condition.

Reference range

The set of values considered normal for a healthy population, used to interpret a calculated result.

Sensitivity

The probability that a positive result correctly identifies a patient with the condition.

Specificity

The probability that a negative result correctly identifies a patient without the condition.

PHQ-9 calculator

A key concept referenced by the PHQ-9: Screen for major depression severity using the validated 9-item Patient Health Questionnaire (PHQ-9). Widely used in primary care.

Depression screening

A key concept referenced by the PHQ-9: Screen for major depression severity using the validated 9-item Patient Health Questionnaire (PHQ-9). Widely used in primary care.

Depression score

A key concept referenced by the PHQ-9: Screen for major depression severity using the validated 9-item Patient Health Questionnaire (PHQ-9). Widely used in primary care.

Mental health assessment

A key concept referenced by the PHQ-9: Screen for major depression severity using the validated 9-item Patient Health Questionnaire (PHQ-9). Widely used in primary care.

PHQ-9 Depression Screening Calculator

Formula Definitions

How to Use This Calculator

Glossary and Definitions

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Frequently Asked Questions