How Reddit Citations Changed in ChatGPT for High-Stakes Health and Medical Consumer Decisions

LLM Authority Index Research | ChatGPT | Health and Medical | July-September 2026

Reddit's visible citation role in ChatGPT health and medical answers changed dramatically during the July through September 2026 research window.

On the balanced 13-vertical July-to-September endpoint, Reddit citation-event share fell from 12.24% to 1.41%, an 88.5% relative decline. Reddit response citation coverage fell from 38.20% to 4.34%, down 88.6%.

The full monthly ChatGPT health panel shows the same break even more clearly. Reddit response coverage moved from 38.20% in July to 8.93% in August and 4.04% in September. Reddit's monthly rank fell from #1 to #3 to #7.

The strict matched-prompt result is even more one-sided. In the locked Article 30 ChatGPT subset, 89 prompt-plus-surface scenarios were paired between July and September. Reddit remained cited in only 1, disappeared in 30, newly appeared in 0, and was absent in 58. Matched coverage fell from 34.83% to 1.12%, down 96.8%.

Answer Capsule

Reddit citation visibility nearly disappeared from ChatGPT's high-stakes health and medical answers between July and September 2026. On the balanced 13-vertical endpoint, Reddit citation-event share fell 88.5%, from 12.24% to 1.41%, while response citation coverage fell 88.6%, from 38.20% to 4.34%. The full monthly panel shows coverage moving 38.20% to 8.93% to 4.04%, with Reddit's rank falling from #1 to #3 to #7. In the locked matched panel, 30 scenarios lost Reddit and none gained it across 89 matched scenarios. The exact two-sided McNemar p-value is approximately 1.86e-9.

Key Findings

• Reddit ranked #1 in July, #3 in August and #7 in September by ChatGPT response citation coverage in the full Health and Medical slice.
• Full-panel response coverage moved from 38.20% to 8.93% to 4.04%.
• Full-panel Reddit citation-event share moved from 12.24% to 3.24% to 1.34%.
• On the balanced 13-vertical endpoint, Reddit event share fell from 12.24% to 1.41%, down 88.5%.
• Balanced response citation coverage fell from 38.20% to 4.34%, down 88.6%.
• The locked strict matched set contained 89 scenarios: 1 both, 30 losses, 0 gains, and 58 neither.
• Matched response coverage fell from 34.83% to 1.12%, down 96.8%.
• The exact two-sided McNemar test gives p ≈ 1.86e-9.
• All 10 of 10 balanced health verticals with measurable July Reddit event share declined by September.
• All 10 of 10 also declined in response coverage.
• Every one of those 10 measurable verticals declined by at least 50% in both event share and response coverage.
• The median event-share decline among those 10 verticals was approximately 87.7%.
• The largest event-share declines were Dental Implants (-100%), STD Tests (-100%), Online Pharmacies (-97.5%), Online Doctors (-94.2%), and Weight Loss and Metabolic Health (-89.0%).
• In the 30 matched Reddit-loss scenarios, no single source replaced Reddit. Healthline and Consumer Reports each newly appeared in 16.7%, HelpGuide in 13.3%, and HearingTracker, Visiting Angels and Psych Central each in 10.0%.
• Article 26 still ranks Reddit #3 overall across the full three-month ChatGPT health source study at 14.0% response coverage, showing how a quarter-wide aggregate can conceal a sharp within-quarter collapse.

Questions This Study Answers

• How much did Reddit citation visibility change in ChatGPT for high-stakes health and medical decisions from July to September 2026?
• Does the decline remain when the same ChatGPT prompt and surface are paired across the two endpoints?
• Which health and medical verticals and replacement sources changed most as Reddit visibility collapsed?

Why This Research Belongs in Daily AI Search Marketing Decisions

Article 54 isolates one source, Reddit, inside one platform, ChatGPT, and one commercial decision family, Health and Medical. That narrow design makes the study useful for day-to-day AI search marketing because it separates four questions that are often collapsed into one visibility score:

1. Where does Reddit rank inside the ChatGPT Health source market?
2. How often is Reddit actually cited, measured both as citation-event share and response citation coverage?
3. Does the same prompt-plus-surface scenario keep or lose Reddit over time?
4. Is Reddit-specific decline occurring inside a stable source market or inside a source market that is itself rotating quickly?

In the three-month ChatGPT Health and Medical source study, Reddit still ranked #3 overall at 14.0% response citation coverage. That aggregate position can coexist with a severe current-month decline: Reddit ranked #1 in July, #3 in August and #7 in September, while full-panel response coverage fell from 38.20% to 8.93% to 4.04% and citation-event share fell from 12.24% to 3.24% to 1.34%.

The balanced 13-vertical endpoint is even more severe. Reddit citation-event share fell 88.5%, from 12.24% to 1.41%, while response citation coverage fell 88.6%, from 38.20% to 4.34%. In the locked matched set, 30 scenarios lost Reddit while none gained it, and matched coverage fell from 34.83% to 1.12%, down 96.8%.

For publishers, that means a strong three-month aggregate position should not be presented as proof that current visibility is stable. For healthcare brands and CMOs, it means ChatGPT source strategy should be monitored with a fixed prompt panel and separate measures for rank, response coverage, citation-event share, matched losses and gains, and source-market turnover.

Article 54 also needs to be interpreted inside a comparatively unstable ChatGPT Health source market. The ChatGPT Health and Medical source study reports that the Top 100 account for 63.5% of domain-response appearances, yet only 45 domains remained in the Top 100 in July, August and September and the median monthly Top 100 Jaccard similarity was only 40.9%. July and September shared just 49 Top 100 domains, or 32.5% Jaccard similarity.

That broad market churn does not explain away the Reddit result. The exact same-prompt panel produced 30 Reddit losses and zero gains, and all 10 balanced Health verticals with measurable July Reddit event share declined in both event share and response coverage. Every one of those 10 verticals declined by at least 50% on both metrics. The median event-share decline was approximately 87.7%, and the median response-coverage decline was 90.0%.

The platform comparison is equally important. In the parent Health and Medical matched study, ChatGPT coverage fell 96.8%, Perplexity 100.0% from a much smaller July base, Google AI Overviews 20.4%, Google AI Mode 20.0%, and Gemini 40.0%. Microsoft Copilot had no captured Reddit citations at either matched endpoint. One blended 'Reddit visibility in AI' score would hide those differences.

The broader Health and Medical Citation Authority Study reports 61.3% median monthly Top 100 persistence, 25.8% median cross-platform Top 100 portability, and an approximate 35.5 percentage-point Persistence-Portability Gap. It also reports 20 domains appearing in all six platform Top 100 lists out of 290 distinct domains in the combined union.

ChatGPT's own Health source market answers a narrower question. Its 40.9% median monthly Top 100 persistence is substantially lower than the category-level 61.3% figure, and the final Health child-study Top 100 lists show ChatGPT sharing 44 domains with Perplexity, 41 with Google AI Mode, 39 with Google AI Overviews, 39 with Gemini and 32 with Microsoft Copilot.

The Persistence-Portability Gap framework therefore helps interpret Article 54 correctly: category-level source authority can be more persistent over time than portable across engines, while one platform's source market can rotate quickly and one individual source inside it can decline even faster. Article 54 should not manufacture a new ChatGPT-specific gap by subtracting 40.9% from a single pairwise platform overlap because those comparison structures are different.

Health and Medical research also needs an additional guardrail. Citation visibility is separate from clinical quality, medical accuracy, safety, endorsement, brand mentions, recommendation rate, rank, sentiment, citation-recommendation coupling, and downstream business outcomes. This study measures the visible source layer around commercial high-stakes health decisions. It does not establish that a cited source caused a healthcare recommendation.

Commercial Action Matrix: What Publishers and CMOs Can Do With the Findings

Where Article 54 Fits in the High-Stakes Consumer Decisions Corpus

Article 54 is a child analysis of two parent studies:

• the Health and Medical Reddit decline study, which provides the balanced family endpoint and matched platform comparison; and
• the ChatGPT Health and Medical source study, which provides the surrounding three-month ChatGPT source market, including Reddit's #3 aggregate rank and 14.0% response coverage, 45 domains present in all three monthly Top 100s, and 40.9% median monthly Top 100 persistence.

The platform-level context comes from the overall ChatGPT Top 100 study. The broader interpretation comes from the 2026 AI Citation Authority Study, the overall Reddit decline study, the cross-platform citation-overlap study, the citation-drift study, and the Persistence-Portability Gap framework. Those studies answer different questions and should not be collapsed into one visibility score.

What We Studied

This article is the ChatGPT platform-specific extension of the broader LLM Authority Index study, Reddit's Decline in AI Citations for High-Stakes Health and Medical Consumer Decisions.

The underlying Article 26 ChatGPT Health and Medical source study contains:

The 318 public-infrastructure exclusions in Article 26 were 198 images.openai.com entries, 88 Mapbox entries and 32 OpenStreetMap entries.

The 14 source vertical labels are:

1. Addiction Treatment Centers
2. Assisted Living Facilities
3. Dental Implants
4. Fertility Clinics
5. Hearing Aids
6. Home Health Care
7. IVF Clinics
8. Medical Alert Systems
9. Mental Health Treatment Centers
10. Online Doctors
11. Online Pharmacies
12. Online Therapy
13. STD Tests
14. Weight Loss and Metabolic Health

Medical Alert Systems has no July source dataset in the frozen archive. It remains part of the three-month source study but is excluded from the balanced July-to-September endpoint. The other 13 verticals are represented at both endpoints.

Article 26 found that Healthline ranked #1 across the full quarter at 21.1% response coverage, followed by Forbes at 14.8% and Reddit at 14.0%. The monthly analysis below shows why a quarter-wide average should not be interpreted as September performance.

The Core Finding: Reddit Collapsed on the Balanced ChatGPT Health Endpoint

Questions This Section Answers

• Did Reddit lose both citation intensity and response reach?
• How large was the balanced ChatGPT decline?
• Was ChatGPT's decline larger than the all-platform Health and Medical decline?

Yes. Both Reddit metrics fell by almost nine tenths on the balanced 13-vertical endpoint.

The broader all-platform Health and Medical parent study reported a 53.5% decline in Reddit citation-event share. ChatGPT declined far more sharply than the family aggregate.

The result is not simply that Reddit slipped several ranking positions. It moved from being cited in more than one third of July ChatGPT health responses to roughly one in twenty-three balanced September responses.

The balanced endpoint removes Medical Alert Systems from September because that vertical has no July source dataset. This prevents a September-only vertical from being treated as though it had a measured July zero.

Reddit Fell Abruptly Across the Three-Month ChatGPT Health Panel

Questions This Section Answers

• Did the decline happen gradually or primarily between July and August?
• How did Reddit's rank change across the quarter?
• How does the full monthly panel differ from the balanced endpoint?

The full monthly platform slice shows that most of the break occurred between July and August, followed by another decline in September.

Reddit lost roughly 29.3 percentage points of response coverage between July and August alone. It then lost another 4.9 percentage points from August to September.

The event-share pattern is similarly steep. Reddit accounted for more than one in eight public ChatGPT health citation events in July, about one in thirty-one in August, and about one in seventy-five in September.

Medical Alert Systems appears in September but not July. Removing that September-only vertical for the balanced endpoint raises September Reddit event share slightly from 1.34% to 1.41% and response coverage from 4.04% to 4.34%. The substantive conclusion does not change.

This is also why Article 26's quarter-wide Reddit coverage of 14.0% should not be read as a current September rate. The high July value materially lifts the three-month aggregate.

The Strict Matched-Prompt Test Shows 30 Losses and Zero Gains

Questions This Section Answers

• Did Reddit decline when prompt wording and ChatGPT surface were held constant?
• How one-sided was the loss-gain pattern?
• Is the matched result statistically meaningful inside this sample?

The locked Article 30 ChatGPT matched panel contains 89 scenarios:

Reddit disappeared in 30 matched scenarios and newly appeared in none.

Matched response coverage fell from 34.83% to 1.12%, a 96.8% relative decline.

The exact two-sided McNemar test gives p ≈ 1.86e-9. Within this matched sample, the one-sided pattern is extremely unlikely under a simple 50/50 turnover model. The test does not identify why Reddit disappeared, and it does not prove a platform policy or causal product change.

The direct frozen-corpus reconstruction reproduces the same 89 scenarios, 1 both, 30 losses, 0 gains and 58 neither, so there is no parent-child denominator discrepancy in this platform slice.

Every Measurable Health Vertical Declined in ChatGPT

Questions This Section Answers

• Was the ChatGPT decline broad across health and medical topics?
• Which verticals declined most sharply?
• How should zero July baselines and the missing Medical Alert Systems month be interpreted?

The platform-specific audit is unusually consistent. All 10 balanced verticals with measurable July Reddit event share declined by September, and every one declined by at least 50%.

Among the 10 verticals with measurable July Reddit event share, the median event-share decline was approximately 87.7%. The median response-coverage decline was 90.0%.

The steepest event-share declines were:

1. Dental Implants: 15.38% to 0.00%, down 100%.
2. STD Tests: 13.04% to 0.00%, down 100%.
3. Online Pharmacies: 14.83% to 0.37%, down 97.5%.
4. Online Doctors: 10.91% to 0.63%, down 94.2%.
5. Weight Loss and Metabolic Health: 13.04% to 1.43%, down 89.0%.

Three balanced verticals had zero Reddit event share in July, so a relative decline cannot be computed from those baselines. Assisted Living Facilities moved from zero to a small non-zero September share. That does not offset the decline across the 10 verticals where Reddit had measurable July visibility.

Medical Alert Systems is not included in the balanced vertical table because it has no July dataset. In September, the ChatGPT Medical Alert Systems slice had a 0.69% Reddit event share and 1.85% response coverage.

What Appeared When Reddit Disappeared?

Questions This Section Answers

• Did one source consistently replace Reddit in the matched loss scenarios?
• Which domains newly appeared most often?
• Does the evidence support a single replacement-source strategy?

No single source replaced Reddit across the 30 matched scenarios where Reddit appeared in July but not September.

Healthline and Consumer Reports were the most common newly appearing sources, but each appeared in only five of 30 loss scenarios.

The replacement set spans general health publishers, consumer publications, hearing specialists, senior-care providers, therapy publishers, government sources and news organizations. That pattern supports source redistribution, not a one-for-one transfer from Reddit to one dominant publisher.

For brands, the practical implication is that there is no evidence here for a universal "replace Reddit with Publisher X" strategy. Source opportunities need to be mapped to the actual commercial prompt cluster.

Platform Differences: ChatGPT Was the Clear Outlier

Questions This Section Answers

• Was the Reddit decline similar across AI platforms?
• How did ChatGPT compare with Google's two AI surfaces?
• Why should health teams report Reddit visibility by platform?

The parent Health and Medical matched study shows large platform differences:

Perplexity reached zero matched Reddit coverage, but from a much smaller July base. ChatGPT is the most commercially consequential outlier because it began with Reddit in more than one third of matched health responses and fell to one persistent scenario out of 89.

Google AI Overviews and Google AI Mode also declined on their matched panels, but by roughly one fifth rather than more than nine tenths.

A single blended "Reddit visibility" KPI would obscure those differences. Health brands and publishers should treat platform as a first-class measurement dimension.

What This Means for Health and Medical Brands and CMOs

Questions This Section Answers

• Should health brands assume Reddit remains a stable ChatGPT citation channel?
• What should replace a single-source authority strategy?
• Which metrics should teams monitor next?

1. Treat Reddit citation visibility as unstable in ChatGPT

The July value was not a durable baseline. Reddit moved from 38.20% full-panel response coverage in July to 4.04% in September.

2. Do not transfer the ChatGPT result to Google

Google AI Overviews and Google AI Mode were much more stable in the matched health panel. A ChatGPT-specific source shock should not be generalized into a platform-wide rule.

3. Build a portfolio of third-party authority

The 30 Reddit-loss scenarios redistributed across Healthline, Consumer Reports, HelpGuide, HearingTracker, Visiting Angels, Psych Central, FDA, news organizations and other sources. The evidence favors diversification.

4. Separate visible citations from brand recommendations

A Reddit URL disappearing does not prove that Reddit stopped affecting the model's answer, and a newly appearing publisher does not prove that it caused a recommendation. Track source citations, brand mentions, recommendation rate, sentiment, comparison placement and first-party citations separately.

5. Manage source strategy by high-intent prompt cluster

Online Pharmacies, Online Doctors, Hearing Aids, Online Therapy and fertility-related questions all lost Reddit at different absolute levels. Publisher outreach and content strategy should follow the prompt clusters that matter commercially.

What This Means for Health and Medical Publishers

The ChatGPT source market changed sharply during the quarter, but the lost Reddit visibility did not transfer cleanly to one publisher.

For publishers, the more defensible commercial opportunity is to document where the domain gains or retains visibility inside the same high-intent prompt sets. Useful evidence includes:

• response citation coverage by health vertical;
• monthly source rank and persistence;
• appearance in Reddit-loss scenarios;
• URL-level citation recurrence;
• cross-platform source coverage; and
• whether brand recommendations move alongside citation visibility.

Article 26 also shows that ChatGPT's health source universe was highly dynamic below the top sources: only 45 domains remained in the monthly Top 100 across all three months, and July-to-September Top 100 Jaccard similarity was only 32.5%.

The defensible claim is measured citation visibility, not that ChatGPT "trusts" a publisher or that a citation caused a brand recommendation.

How This Study Relates to Prior Reddit and Health AI Research

Independent research is directionally consistent with a sharp Reddit decline in ChatGPT during the same quarter, but the exact percentages are not directly comparable.

PromptWatch measured Reddit's share of ChatGPT Search citations averaging 3.83% from July 18 through August 7, 2026, then falling to 0.52% from August 14 through August 17, an 86.4% relative decline. It also measured ChatGPT's use of domain-scoped site: fan-out queries jumping from about 0.4% to nearly 17% on August 8. Article 54 shows a similarly sharp directional break in a different population: full-panel ChatGPT Health response coverage moved 38.20% to 8.93% to 4.04% from July through September, while the balanced endpoint declined 88.6%.

PromptWatch cautioned that the chart established timing rather than causality and said a data-collection issue could not be ruled out. Article 54 therefore treats the timing as contextual evidence, not proof that a specific retrieval, ranking, licensing or product change caused the Health decline.

Ahrefs' September 2026 broad U.S. ChatGPT leaderboard still ranked Reddit #1 at 16.8% mention share, followed by Wikipedia at 7.0%, Consumer Reports at 3.7% and Forbes at 3.1%. That broad all-topic prominence can coexist with Reddit ranking #3 at 14.0% response coverage across this three-month Health source study and only #7 at 4.04% coverage in September. Ahrefs uses a broad U.S. query universe and a mention-share denominator, while Article 54 uses high-stakes commercial Health prompts and reports response citation coverage plus citation-event share.

BrightEdge's August 2026 healthcare comparison found a very different ChatGPT source hierarchy in its tracked prompt set: NIH appeared in 43% of prompts, MedlinePlus in 33%, Mayo Clinic in 27%, CDC in 18% and Cleveland Clinic in 17%. All five were government or nonprofit hospital sources. BrightEdge measured one week, a different healthcare prompt set and citation presence rather than the commercial decision panel used here. The useful agreement is structural: ChatGPT Health source composition changes materially with query population and source definition.

A 2026 medRxiv preprint analyzed 100 HealthSearchQA questions and 615 ChatGPT 5.2 Pro cited sources, reporting 75.7% of citations from established institutional source types. Its consumer-health query population and source-class framework differ substantially from Article 54's commercial decision panel, so the figures should not be merged. The study reinforces the same methodological point: health citation claims need the prompt population and source taxonomy attached to them.

Taken together, the outside research strengthens the case for measurement discipline, not a universal Reddit or healthcare-source narrative. The defensible comparison is direction, platform specificity, population, source definition and methodology, not decimal-point equivalence across unrelated panels.

How This Study Is Different

This study narrows the broader Reddit health trend research to one platform, one high-stakes family and one fixed three-month window.

It combines:

1. a 1,116-response published ChatGPT Health and Medical source slice;
2. a balanced 13-vertical July-to-September endpoint;
3. an 89-scenario locked matched prompt-plus-surface test;
4. both citation-event share and response citation coverage;
5. a 13-vertical balanced audit plus explicit treatment of September-only Medical Alert Systems; and
6. a matched Reddit-loss source redistribution audit.

The narrow question is: how stable was Reddit as a directly cited source in ChatGPT for consequential health and medical consumer decisions during this quarter?

Why AI Citation Studies Can Disagree

Two studies can report different Reddit trends without either one necessarily being wrong.

Query population

High-stakes health and medical prompts are not representative of the entire web. Reddit can behave differently in software, travel, entertainment, general information or troubleshooting queries.

Platform surface

ChatGPT can behave differently from Google AI Overviews, Google AI Mode, Gemini, Perplexity or Microsoft Copilot.

Denominator

Citation-event share and response citation coverage answer different questions. This article reports both and both declined sharply.

Time aggregationArticle 26 reports Reddit at 14.0% coverage across the full three-month ChatGPT health slice. The monthly panel shows 38.20% in July and 4.04% in September. A quarter-wide average can therefore conceal a major directional break.

Missing versus zero

Medical Alert Systems has no July source dataset. That missing month is not converted into a measured zero.

Prompt weighting

This study does not weight prompts by search volume, patient volume, treatment cost, media spend, conversion probability or revenue.

Matching contract

The strict matched panel requires the same normalized prompt and ChatGPT surface in July and September with an unambiguous eligible observation at each endpoint. It answers a narrower question than the monthly aggregate panel.

Domain and infrastructure handling

Article 26 excludes 318 technical infrastructure entries from the public ChatGPT health ranking: 198 images.openai.com entries, 88 Mapbox entries and 32 OpenStreetMap entries. Public domain totals and event-share denominators should be compared only with studies using materially aligned filtering.

The useful conclusion is not that one universal Reddit citation percentage exists. Citation visibility is conditional on platform, category, prompt set, time period, denominator and collection method.

Verticals Covered

The ChatGPT Health and Medical source study covers 14 source vertical labels:

• Addiction Treatment Centers
• Assisted Living Facilities
• Dental Implants
• Fertility Clinics
• Hearing Aids
• Home Health Care
• IVF Clinics
• Medical Alert Systems
• Mental Health Treatment Centers
• Online Doctors
• Online Pharmacies
• Online Therapy
• STD Tests
• Weight Loss and Metabolic Health

Thirteen are present in both July and September. Medical Alert Systems is present later in the quarter but has no July source dataset in the frozen corpus.

Methodology

Source archive

This study uses the frozen July-September 2026 LLM Authority Index archive underlying Article 26 and Article 30.

Eligibility

A record is eligible when it is:

• in July, August or September 2026;
• assigned to the ChatGPT platform family;
• associated with the Health and Medical family; and
• not explicitly marked as an extraction failure.

Article 26 reports zero explicit extraction failures in this ChatGPT Health and Medical slice.

Exact-repeat anti-double-counting

An observation is treated as an exact analytical repeat when all of the following match:

• report month;
• exact raw platform/source surface;
• normalized prompt text; and
• exact set of original citation URLs.

One analytical record is retained while source-dataset memberships are preserved for vertical analysis.

Prompt normalization

Prompt text is normalized with Unicode NFKC normalization, case folding, whitespace collapse and trimming.

Domain normalization

Citation URLs are parsed to hostname, lowercased, stripped of a leading www., and consolidated to registrable domain using Public Suffix List logic.

Public infrastructure exclusions

The Article 26 public rule excludes 198 images.openai.com entries, 88 Mapbox entries and 32 OpenStreetMap entries. The platform-specific child calculations use the same public denominator contract.

Reddit identification

Reddit is identified at the registrable-domain level as reddit.com.

Citation-event share

Reddit citation-event share = Reddit citation events / all eligible public citation events

A response can contribute more than one Reddit citation event if multiple eligible Reddit URLs appear.

Response citation coverage

Reddit response citation coverage = eligible responses citing Reddit at least once / all eligible responses

Reddit counts no more than once per response for this metric.

Balanced endpoint

The July-to-September balanced endpoint excludes Medical Alert Systems because the frozen archive contains no July source dataset for that vertical. The other 13 source verticals are present at both endpoints.

Matched prompt-plus-surface test

The headline matched panel is inherited from Article 30 and reproduced by the direct record-level reconstruction. It contains 89 scenarios, with 1 both, 30 losses, 0 gains, and 58 neither.

Vertical audit

The vertical table is recalculated directly from the frozen ChatGPT record-level corpus using the same public infrastructure exclusions as Article 26.

Replacement-source audit

For matched scenarios where Reddit appeared in July but not September, the analysis identifies registrable domains present in September but absent from the paired July citation set. Newly appearing domains can co-occur, so this is not a mutually exclusive attribution model.

Limitations

1. The study covers one frozen three-month research window and should not be treated as a permanent ChatGPT rule.
2. Prompt sets are research panels, not search-volume-weighted market-share samples.
3. Visible citation does not prove recommendation causality, hidden retrieval influence or training-data use.
4. The study cannot observe every internal retrieval or ranking step.
5. Several health source labels overlap semantically, especially Fertility Clinics and IVF Clinics.
6. Some verticals have very small July ChatGPT samples, including Dental Implants, Assisted Living Facilities and Mental Health Treatment Centers. Relative percentages from tiny bases should be interpreted cautiously.
7. Medical Alert Systems has no July source dataset and is excluded from the balanced endpoint.
8. Newly appearing September domains are descriptive co-occurrences, not proven replacements for Reddit.
9. ChatGPT behavior can vary by geography, account state, model version, product surface and rollout.
10. The statistical test measures the matched loss-gain imbalance, not the reason for the change.

Commercial Disclosure

LLM Authority Index is affiliated with CiteWorks Studio and related AI-search research and services. This research is designed to document observed AI citation behavior. Commercial relationships do not alter the frozen source corpus, eligibility rules, matching logic or published denominators.

No company can purchase a ranking, recommendation, score or position in this study. Citation visibility should not be interpreted as an endorsement by LLM Authority Index or by ChatGPT.

References

1. LLM Authority Index. The 2026 AI Citation Authority Study: Which Websites Does AI Cite for High-Stakes Decisions? https://llmauthorityindex.com/resources/research/2026-ai-citation-authority-study-high-stakes-consumer-decisions
2. LLM Authority Index. The Most-Cited Websites in AI for High-Stakes Health and Medical Consumer Decisions. https://llmauthorityindex.com/resources/research/most-cited-websites-ai-health-medical-high-stakes-consumer-decisions
3. LLM Authority Index. Reddit's Decline in AI Citations for High-Stakes Health and Medical Consumer Decisions. https://llmauthorityindex.com/resources/research/reddit-ai-citation-decline-health-medical-high-stakes-consumer-decisions
4. LLM Authority Index. The 100 Most-Cited Websites in ChatGPT for High-Stakes Health and Medical Consumer Decisions. https://llmauthorityindex.com/resources/research/top-100-chatgpt-citations-health-medical-high-stakes-consumer-decisions
5. LLM Authority Index. The Persistence-Portability Gap: Why AI Citation Authority Persists Over Time but Fragments Across Platforms. https://llmauthorityindex.com/resources/measurement/persistence-portability-gap
6. PromptWatch. Why Did ChatGPT Stop Citing Reddit? Inside the August 2026 Citation Collapse. https://promptwatch.com/blog/chatgpt-stop-citing-reddit
7. Ahrefs. The 50 Most-Cited Websites in ChatGPT (September 2026). https://ahrefs.com/blog/most-cited-domains-in-chatgpt/
8. BrightEdge. Institution or Platform: What Health and Finance Citations Reveal About ChatGPT and Google AI Overviews. https://help.brightedge.com/resources/weekly-ai-search-insights/ai-overviews-chatgpt-authority-health-finance
9. Jacques E, et al. Authority Signals in AI Cited Health Sources: A Framework for Evaluating Source Credibility in ChatGPT Responses. medRxiv. 2026. https://www.medrxiv.org/content/10.64898/2026.01.22.26344576v1.full

Related LLM Authority Index Research

Corpus foundation and measurement framework

• 2026 AI Citation Authority Study
• Overall Reddit Citation Decline Study
• Cross-Platform Citation Overlap Study
• AI Citation Drift Study
• Overall ChatGPT Top 100 Study
• Persistence-Portability Gap Framework

Health and Medical source-market branch

• All-Platform Health and Medical Citation Authority Study
• Google AI Overviews Health and Medical Citation Sources
• Google AI Mode Health and Medical Citation Sources
• ChatGPT Health and Medical Citation Sources
• Perplexity Health and Medical Citation Sources
• Gemini Health and Medical Citation Sources
• Microsoft Copilot Health and Medical Citation Sources

Health and Medical Reddit-trend branch

• Health and Medical Reddit Decline Parent Study
• Google AI Overviews Reddit Trend
• Google AI Mode Reddit Trend
• ChatGPT Reddit Trend
• Perplexity Reddit Trend
• Gemini Reddit Trend
• Microsoft Copilot Reddit Trend