Patient Health Questionnaire (PHQ-9) Assessment

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Depression symptoms over the past two weeks are summarized by a short nine item questionnaire that translates everyday experiences into a single severity score. The result helps you understand where your recent mood and energy sit on a well used clinical scale and what that might suggest for next steps.

You read each statement and pick how often it applied, then review a total score with clear bands and a few helpful breakdowns. Many people use it to check change over time and to bring a concise snapshot to a conversation with a clinician or a trusted supporter.

You provide one choice per item and you receive a total, a simple gauge, and three subscores that group related symptoms. As an example, someone who often feels low and has broken sleep may score higher on interest, mood, and rest which pushes the total upward.

Use consistent judgment across items and focus on the same two week window to make results comparable. Results are a guide and not a diagnosis, and thoughts of self harm call for urgent support in your area. This tool provides informational estimates and does not substitute professional advice.

Technical Details:

The Patient Health Questionnaire nine item scale (PHQ‑9) captures the frequency of depressive symptoms during the previous two weeks. Each item is scored 0 for “Not at all”, 1 for “Several days”, 2 for “More than half the days”, or 3 for “Nearly every day”.

The total score adds the nine responses to a 0–27 scale that tracks overall symptom burden. In addition, three subscores summarize common groupings: a Core pair (interest and mood), a Somatic cluster (sleep, energy, appetite, and psychomotor change), and a Cognitive pair (self‑view and concentration). Item 9 is treated as a distinct safety screen.

Identical responses always yield the same totals. Interpret values near a band edge with care, and compare like with like by using the same recall window and context across repeats.

S = \sum_{i = 1}^{9} x_{i}

\begin{array}{lcl} C & = & x_{1} + x_{2} \\ M & = & x_{3} + x_{4} + x_{5} + x_{8} \\ A & = & x_{6} + x_{7} \\ R & = & x_{9} \end{array}

Symbols and units
Symbol	Meaning	Unit/Datatype	Source
x1	Interest or pleasure	integer 0–3	Input
x2	Low mood or hopelessness	integer 0–3	Input
x3	Sleep difficulty or excess	integer 0–3	Input
x4	Low energy or fatigue	integer 0–3	Input
x5	Appetite change	integer 0–3	Input
x6	Self‑view or guilt	integer 0–3	Input
x7	Concentration	integer 0–3	Input
x8	Psychomotor change	integer 0–3	Input
x9	Thoughts of self‑harm	integer 0–3	Input
S	Total score	integer 0–27	Derived
C	Core subscore	integer 0–6	Derived
M	Somatic subscore	integer 0–12	Derived
A	Cognitive subscore	integer 0–6	Derived
R	Safety screen (item 9)	integer 0–3	Input

Worked example

Suppose responses are 2, 1, 2, 1, 0, 1, 1, 2, 0. Then:

S = 2 + 1 + 2 + 1 + 0 + 1 + 1 + 2 + 0 = 10

\begin{array}{lcl} C & = & 2 + 1 = 3 \\ M & = & 2 + 1 + 0 + 2 = 5 \\ A & = & 1 + 1 = 2 \\ R & = & 0 \end{array}

A total of 10 falls in the “Moderate” band below and the safety screen is negative.

Interpretation thresholds
Threshold band	Lower bound	Upper bound	Interpretation	Action cue
Minimal	0	4	No evidence of major depression.	Maintain healthy habits; monitor.
Mild	5	9	Mild depressive symptoms.	Self‑help and recheck soon.
Moderate	10	14	Noticeable impact on life.	Discuss care options.
Moderately severe	15	19	Marked burden.	Seek professional evaluation.
Severe	20	27	High symptom load.	Urgent clinical support.

Units, precision, and rounding: inputs are ordinal integers with a step of 1; totals and subscores are exact integers; no rounding is applied.

Validation rules
Field	Type	Min	Max	Step/Pattern	Error text	Placeholder
Each item response	Integer	0	3	Step 1; encoded as a nine‑character string of 0–3 or “-” for missing	None; progress prompts completion	Not used
Encoded parameter “r”	String	9	9	Regex: `^[0-3\-]{9}$`	Invalid strings are ignored	Not used

I/O formats
Input	Accepted families	Output	Encoding/Precision	Rounding
On‑screen choices	Radio 0–3 per item	Total, subscores, gauge	Integer totals	None
Shareable state	Query parameter “r”	Prefilled responses	Nine characters (0–3 or “-”)	None
Answer exports	CSV, DOCX	Answer table	Local file generation	None

Networking and storage: responses are handled in the page and are not sent to a server; optional exports are created locally. One charting script is fetched to render the gauge; assessment data is not transmitted.

Diagnostics and determinism: the same selections always produce the same totals and bands. The gauge simply visualizes the integer total on a 0–27 arc.

Security considerations: the shareable parameter includes your answers; only share a link if you are comfortable revealing responses. Avoid pasting sensitive details into exported files on shared devices.

Assumptions & limitations

Assumes a two‑week recall window and consistent interpretation of frequency terms.
Not a diagnosis; clinical judgment and context remain essential.
Band edges may not reflect meaningful change for every person.
Subscores are heuristic groupings, not independent scales.
Self‑report can be influenced by memory, stress, or social context.
Item 9 is a screen, not a risk assessment.
Comparisons across people can be misleading; prefer within‑person trends.
Heads‑up Exported files may persist on the device if not deleted.

Edge cases & error sources

Incomplete responses delay totals until all items are answered.
Invalid “r” strings are ignored and the page starts fresh.
Accidental double clicks can momentarily flip selections before settling.
Very low or very high totals may reflect atypical short‑term situations.
Band changes from a one‑point swing near a threshold can occur.
Copy or download may be blocked by strict browser permissions.
File‑type handlers may open DOCX in a viewer without editing support.
Accessibility settings that enlarge text can wrap labels unexpectedly.
Older devices may render the gauge slowly on window resize.
Shared links expose encoded responses to anyone with the URL.

How‑to Guide:

Complete the nine item scale and read the result with clear bands and next‑step cues.

Read each statement covering the past two weeks.
Select how often it applied to you from the four choices.
Repeat until all nine items show as answered.
Review the total, subscores, and the gauge.
Optionally copy answers, download CSV, or export DOCX.

Example: If sleep and energy are often affected and mood is low some days, expect higher somatic and core subscores with a mid‑range total.

Re‑use the same window and context on future runs to compare changes.

FAQ:

Is my data stored?

Responses stay on the device. No server storage is used. Exports are created locally and remain on the device until you remove them.

Privacy note

How accurate is the result?

The scale reflects self‑reported frequency of symptoms. It is reliable for tracking change over time but it does not diagnose a condition on its own.

Interpretation note

What are the units?

Each item is an integer from 0 to 3 and the total runs from 0 to 27. Subscores are simple sums over specific item groups.

Units and ranges

Can I use this offline?

Yes after the page loads. Interactions, scoring, and exports work without a connection. No data upload occurs during use.

Availability

Does the gauge change the score?

No. It is a visual indicator only. The underlying score is the sum of the nine item selections.

Visualization

How do I interpret “borderline” totals?

Scores near a threshold can shift bands with a one‑point change. Look at subscores and patterns across repeats, and consider professional input.

Threshold caution

Can I share a link with my selections?

Yes, a short parameter can encode responses. Only share if you are comfortable with others seeing that information.

Safety

Is there any cost or license?

Use terms depend on the site hosting this page. There is no sign‑in and no purchase prompt in this package.

Usage

Troubleshooting:

No total appears: answer all items; the score shows when complete.
Gauge missing: reload the page so the chart script can initialize.
Copy fails: grant clipboard permission or use the download option.
CSV opens oddly: import with UTF‑8 and comma delimiter.
DOCX will not open: ensure a compatible editor is installed.
Selections reset: avoid using the back button while responding.
Dark mode contrast: switch theme if labels are hard to read.

If item 9 is anything other than “Not at all” and you feel unsafe, seek urgent support in your area.

Advanced Tips:

Tip Re‑take at the same time of day for better comparability.
Tip Note major events; context explains jumps more than small changes.
Tip Watch subscores to spot which domain is driving the total.
Tip Use exports to keep a dated record when tracking over weeks.
Tip If near a threshold, look for consistent movement across two runs.
Tip Pair the snapshot with sleep, movement, or routine notes for insight.

Glossary:

PHQ‑9: Patient Health Questionnaire nine item scale.
Total score: Sum of all nine item responses, range 0–27.
Core subscore: Interest and mood pair (items 1 and 2).
Somatic subscore: Sleep, energy, appetite, and psychomotor items.
Cognitive subscore: Self‑view and concentration items.
Safety screen: Item 9 about thoughts of self harm.
Band: Score category such as Mild or Moderate.
Recall window: The specific two week period used for responses.

Patient Health Questionnaire (PHQ-9) Assessment

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Technical Details:

Assumptions & limitations

Edge cases & error sources

How‑to Guide:

FAQ:

Troubleshooting:

Advanced Tips:

Glossary:

Patient Health Questionnaire (PHQ-9) Assessment

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Introduction:

Technical Details:

Assumptions & limitations

Edge cases & error sources

How‑to Guide:

FAQ:

Troubleshooting:

Advanced Tips:

Glossary: