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

LLM Authority Index Research | High-Stakes Consumer Decisions | Health and Medical | Perplexity | July-September 2026

Reddit lost all of its visible citation presence inside the strict matched Perplexity health panel between July and September 2026.

Across 92 exact prompt-plus-Perplexity scenarios observed at both endpoints, Reddit appeared in 3 July scenarios and 0 September scenarios.

The matched table contained:

• 3 Reddit losses
• 0 Reddit gains
• 0 persistent Reddit citations
• 89 scenarios citing Reddit in neither endpoint month

Matched Reddit response coverage therefore fell from 3.26% to 0.00%, a 100% relative decline inside the strict paired subset.

Using the published 3-loss, 0-gain contingency table, the derived exact two-sided McNemar result is p = 0.25. That is not statistically significant at a conventional 0.05 threshold.

The absolute count is small, so the strongest conclusion is directional rather than universal:

Every matched Perplexity health scenario that cited Reddit in July stopped citing Reddit by September, but only three matched July-positive cases existed.

The broader three-month source market shows that Reddit still mattered earlier in the quarter.

Across 858 eligible deduplicated Perplexity health responses, Reddit appeared in 29 responses, or 3.38%, and generated 30 of 2,149 substantive public-facing citation events, approximately 1.40% of the cleaned citation pool.

Reddit ranked #11 overall across the full three-month Perplexity health and medical source market.

Its monthly rank moved from #4 in July to #5 in August and then #41 in September.

That combination is commercially important. Reddit remained close to the top of Perplexity's health source market in July and August, but its September position weakened sharply.

Important: The parent Health and Medical Reddit study publishes platform-specific matched counts for Perplexity but does not publish a separate Perplexity-wide balanced July-to-September aggregate event-share or response-coverage table. This child article therefore does not invent a platform-specific aggregate endpoint percentage. It uses the published matched panel for longitudinal Perplexity endpoint inference and the published three-month Perplexity source study for quarter-wide context.

Answer Capsule

Did Reddit citation visibility decline in Perplexity for high-stakes health and medical decisions from July to September 2026? Yes in the strict matched panel. Across 92 exact prompt-plus-Perplexity scenarios, Reddit recorded 3 losses and 0 gains, moving matched response coverage from 3.26% to 0.00%. The derived exact McNemar result is p = 0.25, so the matched result is directionally negative but based on too few discordant cases to establish a statistically significant platform-wide change on its own. Across the full three-month Perplexity health source market, Reddit still ranked #11, appearing in 29 of 858 responses, but its monthly rank fell from #4 in July to #41 in September.

Key Findings

• The strict matched Perplexity health panel contained 92 exact prompt-plus-platform scenarios.
• Reddit recorded 3 matched losses and 0 gains.
• There were 0 persistent Reddit citations across the matched endpoints.
• Matched Reddit response coverage fell from 3.26% to 0.00%.
• The matched relative decline was 100%.
• The derived exact two-sided McNemar result is p = 0.25.
• The small discordant count means the result should be treated as directional rather than a precise platform-wide decline rate.
• Across the full three-month Perplexity health source market, Reddit appeared in 29 of 858 responses, or 3.38%.
• Reddit generated 30 of 2,149 substantive public-facing citation events, approximately 1.40%.
• Reddit ranked #11 overall across the three-month Perplexity health source market.
• Reddit's monthly rank moved #4 in July, #5 in August and #41 in September.
• Reddit appeared across 7 of the 14 health and medical source labels in the three-month source ranking.
• The Perplexity health source market contained 556 registrable cited domains and 1,981 domain-response appearances.
• 218 technical or unusable citation entries were excluded from the public publisher ranking.
• Healthline ranked #1 at 12.82% response coverage, followed by SeniorLiving.org at 8.97%, NCOA.org at 8.86%, HelpGuide.org at 7.34%, and GoodRx at 5.24%.
• Only 32 of the health Top 100 domains also appeared in Perplexity's broader High-Stakes Consumer Decisions Top 100.
• Reddit weakened much more sharply in monthly rank than the leading health-specialist sources.
• Broad all-topic Perplexity research can still rank Reddit #1 while this narrower health source market shows a major September decline.

Questions This Study Answers

• Did Reddit persist when the exact same health prompt was compared in Perplexity at both endpoints?
• How important was Reddit across the full three-month Perplexity health source market?
• Why can broad Perplexity research rank Reddit first while health-specific September visibility falls sharply?

Why This Research Belongs in Daily AI Search Marketing Decisions

Article 64 isolates one source, Reddit, inside one platform, Perplexity, and one commercial decision family, Health and Medical. Its operating value comes from keeping three different measurements separate: quarter-wide source importance, same-prompt endpoint persistence, and broader source-market turnover.

1. How important was Reddit across the full three-month Perplexity health source market?
2. Did the exact same prompts retain Reddit between July and September?
3. How should marketers interpret that change inside a rapidly rotating health source market?

Across the full three-month Perplexity Health and Medical source study, Reddit ranked #11 overall at 3.38% response citation coverage. It appeared in 29 of 858 eligible responses and generated 30 of 2,149 substantive public-facing citation events, about 1.40% of the cleaned event pool.

That quarter-wide rank masks a sharp current-state change. Reddit's monthly rank moved #4 in July, #5 in August and #41 in September.

The strict matched panel points in the same direction. Across 92 exact prompt-plus-Perplexity scenarios, Reddit produced 3 losses, 0 gains, 0 persistent citations and 89 neither-month scenarios. Matched response coverage fell from 3.26% to 0.00%, a 100% decline inside the matched subset. The derived exact two-sided McNemar result is p = 0.25.

That p-value matters. The matched panel is directionally negative, but only three discordant cases exist. The result should therefore be described as complete matched loss among the small number of July-positive Perplexity health scenarios, not as independently conclusive evidence of a platform-wide causal shift.

Article 64 does not publish a separate Perplexity-specific balanced aggregate July-to-September event-share or response-coverage percentage because the frozen parent study does not publish those platform-specific aggregate values. The article uses the published matched panel for Perplexity longitudinal inference and the three-month Perplexity source study for quarter-wide context.

The surrounding Perplexity health source market is relatively diffuse and highly dynamic. Its Top 10 account for only 27.5% of domain-response appearances, while the Top 100 account for 66.0%. Only 35 domains remained in the monthly Top 100 across July, August and September, and median monthly Top 100 Jaccard similarity was only 29.0%.

That broader market churn does not erase the Reddit signal. Reddit fell from #4 to #41 between July and September, and every matched July-positive Reddit scenario disappeared by September. The defensible interpretation is a Reddit-specific deterioration occurring inside a Perplexity health market that was already rotating materially.

Category specialization is substantial. Only 32 of Perplexity's Health and Medical Top 100 domains also appear in Perplexity's broader High-Stakes Consumer Decisions Top 100, a 19.0% Jaccard similarity. The final Health child-study Top 100 lists show Perplexity sharing 50 domains with Google AI Overviews, 49 with Google AI Mode, 46 with Gemini, 44 with ChatGPT and 38 with Microsoft Copilot.

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. The final six Health platform studies contain 290 distinct Top 100 domains in their union. Only 20 domains appear in all six platform Top 100s, while 161 appear in only one.

The Persistence-Portability Gap framework helps interpret Article 64 correctly. Health source authority is more persistent over time than universally portable across engines, while Perplexity's own Health source market rotates much more quickly. Article 64 should not manufacture a Perplexity-specific gap by subtracting 29.0% temporal persistence from one pairwise platform overlap because those comparison structures are different.

The parent Health and Medical Reddit decline study provides broader category context. Across the balanced all-platform family, Reddit citation-event share fell from 2.13% to 0.99%, down 53.5%, while response citation coverage fell from about 6.91% to 3.63%, down about 47.5%. Thirteen health verticals had both endpoint datasets, ten had measurable July Reddit event share, and all 10 of those 10 declined. Those are family-level results, not Perplexity-specific aggregate endpoint metrics.

Perplexity also requires source-surface cleanup. The source study excludes 218 technical or unusable entries from the public publisher ranking: 171 Perplexity thumbnail-CDN URLs, 33 st.perplexity.ai static assets, 13 Mapbox infrastructure entries and 1 unusable URL.

Citation visibility should remain separate from brand mentions, recommendation rate, rank, sentiment, citation-recommendation coupling, clinical quality, treatment safety and downstream business outcomes. A visible citation does not prove that a source caused Perplexity to recommend a provider, product, clinic or treatment, and citation frequency is not a medical-quality score.

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

Need company- or vertical-specific tracking? Publishers and companies can contact LLM Authority Index for individual vertical research, recurring AI citation tracking and company-level reporting. The research service does not sell rankings, inclusion or recommendation placement.

Where Article 64 Fits in the High-Stakes Consumer Decisions Corpus

Article 64 is a child analysis of two parent studies:

• the Health and Medical Reddit decline study, which provides the balanced family context, platform-specific matched comparison and broader replacement analysis; and
• the Perplexity Health and Medical source study, which provides the surrounding three-month source market, including Reddit's #11 aggregate rank and 3.38% response coverage, 35 domains present in all three monthly Top 100s and 29.0% median monthly Top 100 persistence.

The platform-level context comes from the overall Perplexity 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.

The Core Matched Finding: Three Reddit Losses and Zero Gains

Questions This Section Answers

• What happened when the exact prompt and Perplexity platform were held constant?
• Did any matched scenario gain Reddit by September?
• How strong is the statistical evidence?

The strict matched panel controls more tightly than a pooled source ranking.

A scenario qualifies only when the same normalized prompt on the same Perplexity platform family has one eligible analytical observation in July and one in September.

92 scenarios met that contract.

Matched Reddit response coverage moved from:

3 / 92 = 3.26%

to:

0 / 92 = 0.00%

That is a 100% relative decline in the strict matched subset.

Every matched Perplexity health scenario that cited Reddit in July lost Reddit by September.

No matched scenario gained Reddit.

However, only three discordant pairs exist.

Using the published counts, the derived exact two-sided McNemar p-value is 0.25.

That does not meet a conventional 0.05 significance threshold.

The correct interpretation is therefore:

The matched Perplexity health sample moves entirely in the negative direction, but the number of Reddit-positive July cases is too small for a strong standalone statistical conclusion.

Why This Article Does Not Publish a Separate Perplexity Aggregate Endpoint Percentage

Questions This Section Answers

• Why is there no Perplexity-specific July-to-September event-share table in this article?
• Is the metric missing or intentionally omitted?
• What source evidence is available instead?

The parent Health and Medical Reddit study publishes:

• the balanced all-platform family endpoint;
• platform-specific matched counts and matched coverage;
• the all-platform replacement analysis; and
• the cross-platform comparison.

It does not publish a separate Perplexity-specific balanced aggregate July event share, September event share, July response coverage and September response coverage.

The supporting Perplexity source study publishes:

• three-month source totals;
• three-month domain coverage;
• citation events;
• monthly rank;
• monthly Top 100 overlap; and
• platform-comparison context.

It does not publish month-specific Reddit response counts or month-specific Reddit citation-event counts.

Those source limitations matter.

This article therefore does not reverse-engineer or guess a separate Perplexity aggregate endpoint percentage.

The longitudinal claim is based on the published 92-scenario matched panel.

The quarter-wide source-market claim is based on the published 858-response Perplexity health source study.

That keeps the child article inside the frozen evidence actually available in the Drive.

Reddit Still Ranked #11 Across the Full Three-Month Perplexity Health Market

Questions This Section Answers

• Did Reddit disappear from Perplexity health answers for the entire quarter?
• How important was Reddit in the pooled source market?
• What was Reddit's quarter-wide response coverage?

Reddit remained a meaningful Perplexity health source across the pooled July-September window.

This pooled-quarter result should not be confused with September-only current-state visibility.

The quarterly denominator combines July, August and September.

Strong July and August performance can preserve a relatively high pooled-quarter rank even after a September drop.

Reddit's Monthly Rank Fell From #4 to #41

Questions This Section Answers

• Did Reddit decline smoothly month by month?
• How large was the September rank break?
• Why does monthly rank matter alongside the matched panel?

Reddit's monthly rank moved:

Reddit remained near the top of the Perplexity health source market in July and August.

By September, it had fallen thirty-six positions from August and thirty-seven positions from July.

That monthly rank movement is directionally consistent with the strict matched result.

The two measurements are different:

• monthly rank is a market-position metric;
• matched coverage is a same-prompt persistence metric.

Both point toward weaker September Reddit visibility.

The Leading Health Sources Were Much More Persistent

Questions This Section Answers

• Did all leading health sources fall as sharply as Reddit?
• Which publishers remained strongest?
• Was Reddit's movement unusual relative to the category leaders?

The top of Perplexity's health source market remained relatively stable.

The monthly rank sequences show the contrast:

• Healthline: #1 → #3 → #1
• SeniorLiving.org: #8 → #1 → #3
• NCOA.org: #3 → #2 → #4
• HelpGuide.org: #22 → #8 → #2
• GoodRx: #2 → #7 → #24
• Reddit: #4 → #5 → #41

Reddit's September drop was much sharper than the recurring health-specialist leaders.

Perplexity's Health Source Market Was Highly Category-Specific

Questions This Section Answers

• How much did the health Top 100 overlap with Perplexity overall?
• Would a broad Perplexity source leaderboard capture the right healthcare publishers?
• Why does category-specific measurement matter?

Only 32 of the health and medical Top 100 domains also appeared in Perplexity's broader High-Stakes Consumer Decisions Top 100.

That is 19.0% Jaccard similarity.

The category effect is substantial.

A broad Perplexity authority list would miss many sources that matter heavily inside:

• hearing aids;
• medical alert systems;
• fertility and IVF;
• online pharmacy;
• online therapy;
• addiction treatment;
• mental health treatment;
• senior care; and
• other consumer-health buyer journeys.

That helps explain why broad Perplexity source studies can produce a very different Reddit rank from this health-specific panel.

Specialist Health Sources Over-Indexed Sharply

Questions This Section Answers

• Which health specialists were unusually strong in Perplexity?
• Did broad publishers dominate every vertical?
• What does that mean for healthcare earned-media strategy?

The supporting Perplexity source study found strong category lift for several specialist domains.

It reports that:

• NCOA.org has about 6.6x its Perplexity-wide coverage inside the health slice.
• HelpGuide.org has about 6.6x its Perplexity-wide coverage.
• GoodRx has about 6.6x.
• HearingTracker has about 6.6x.
• Medical News Today has about 5.2x.

Vertical leadership also varied sharply.

Examples include:

• HearingTracker and NCOA leading hearing-aid prompts.
• SeniorLiving.org and NCOA leading medical-alert prompts.
• GoodRx and Amazon rising in online-pharmacy prompts.
• CCRM IVF leading both Fertility Clinics and IVF Clinics.
• Provider and specialist sites leading multiple treatment-oriented verticals.

The implication is that Reddit's decline should not be interpreted as a simple handoff to one broad publisher.

Perplexity's health source ecosystem is fragmented and highly vertical-specific.

Perplexity's Technical Citation Layer Requires Cleanup

Questions This Section Answers

• How many technical or unusable entries were excluded?
• Which infrastructure sources were removed?
• Could technical filtering explain Reddit's rank?

The raw deduplicated Perplexity health slice contained 2,367 citation-array entries before public-source filtering.

The source study excluded 218 obvious technical or unusable entries:

That leaves 2,149 substantive public-facing citation events.

The filtering contract removes infrastructure from the publisher analysis.

It does not explain Reddit's matched endpoint decline because the matched Reddit analysis uses the frozen source rules consistently across endpoints.

Perplexity's Matched Health Pattern Differed From the Other Platforms

Questions This Section Answers

• How did Perplexity compare with ChatGPT, Gemini and Google's AI search surfaces?
• Which platforms showed the strongest same-prompt Reddit losses?
• Why is one blended Reddit metric misleading?

The parent Health and Medical study reports:

ChatGPT had by far the largest matched break.

Perplexity also reached zero matched September coverage, but from only three July-positive cases.

Google AI Overviews and Google AI Mode retained much more Reddit continuity.

Gemini declined from a low baseline.

Copilot had no matched Reddit baseline at either endpoint.

This is why "Reddit citations in AI" should not be represented as one platform-neutral KPI.

The Parent Health Family Declined More Than Half in Event Share

Questions This Section Answers

• Was Perplexity part of a broader health-family decline?
• How much did Reddit decline across the full health panel?
• How broad was the decline by vertical?

Across the balanced all-platform Health and Medical family, Reddit citation-event share fell from 2.13% to 0.99%, a 53.5% relative decline.

Response citation coverage fell from approximately 6.91% to 3.63%, down about 47.5%.

Thirteen health and medical verticals had both July and September datasets.

Ten of those had measurable July Reddit citation-event share.

All 10 of 10 declined by September.

The median decline across those measurable verticals was 44.5%.

Those figures are all-platform family results, not Perplexity-only aggregate endpoint metrics.

They provide category context without being misrepresented as a Perplexity-specific statistic.

No Single Publisher Replaced Reddit Across the Parent Health Study

Questions This Section Answers

• Did one publisher consistently replace Reddit?
• Which sources most often newly appeared after Reddit losses?
• Can those results be attributed specifically to Perplexity?

The parent health study examined 85 matched Reddit-loss scenarios across all tracked platforms.

The most common newly appearing domains were:

No source consistently replaced Reddit.

These are all-platform health-family results, not a Perplexity-only replacement table.

The Perplexity child evidence is narrower: three matched Reddit losses, zero gains and zero persistent matched citations.

Which Health and Medical Verticals Are Represented?

The full Perplexity health source study contains 14 source labels:

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 file in the frozen corpus.

The parent balanced July-to-September health-family endpoint therefore uses 13 comparable verticals.

The three-month Perplexity source ranking includes all 14 source labels.

Reddit appears across 7 of them.

How This Study Relates to Prior Perplexity and Health Citation Research

Questions This Section Answers

• How can broad Perplexity research rank Reddit #1 while this Health panel shows a September collapse in rank?
• What does broader Q3 research say about Perplexity's social-source behavior?
• What does independent healthcare citation research say about engine-specific source hierarchies?

Ahrefs' September 2026 broad U.S. Perplexity study ranks Reddit #1 at 21.6% mention share, ahead of YouTube at 20.8%. Ahrefs uses an all-topic U.S. query universe and defines mention share as a domain's share of citations among the top sources in its ranking. Article 64 instead uses high-stakes commercial Health and Medical prompts, reports response citation coverage plus citation-event share, and measures a three-month category-specific panel.

Those findings can coexist. Reddit can remain Perplexity's largest broad all-topic source in September while falling from #4 to #41 inside a narrower high-stakes Health source market.

Tinuiti's Q3 2026 AI Citation Trends Report independently identifies Perplexity as a notable exception to the broader pattern of AI platforms reaching or approaching Q3 highs in social citation share. Tinuiti tracks different commercial categories and broader social-source behavior, so its percentages should not be converted into a Reddit-specific Health benchmark.

BrightEdge's August 2026 healthcare citation research also shows that source hierarchies can differ sharply by engine even inside one sensitive category. In its tracked healthcare prompts, ChatGPT's leading sources were government agencies and hospital systems, while Google AI Overviews showed a much stronger YouTube presence. BrightEdge measures a different prompt population, period and engine set, but the methodological lesson is directly relevant: health citation strategy should be built at the platform and category level, not inferred from one broad authority list.

Taken together, the outside research strengthens the case for measurement discipline, not a universal Reddit or healthcare-authority narrative. The defensible comparison is source-role structure, platform, category, time period and denominator, not decimal-point equivalence across unrelated panels.

How This Study Relates to the Parent Health Reddit Study

The parent Health and Medical study found that Reddit's balanced all-platform citation-event share fell from 2.13% to 0.99%, a 53.5% relative decline.

Balanced response citation coverage fell from approximately 6.91% to 3.63%, down about 47.5%.

Across the all-platform strict matched panel, Reddit losses outnumbered gains 85 to 32.

Perplexity contributed:

• 3 losses
• 0 gains
• 0 persistent citations
• 89 neither-month scenarios

That produces a Perplexity matched coverage move from 3.26% to 0.00%.

This child analysis adds three-month Perplexity source-market context without pretending that the all-platform aggregate decline is a Perplexity-specific endpoint percentage.

How This Study Is Different

This article narrows the broader health Reddit research to one platform, one high-stakes family and one three-month research period.

It combines:

1. a 92-scenario strict matched prompt-plus-Perplexity panel;
2. a 858-response three-month Perplexity Health and Medical source slice;
3. both matched endpoint coverage and pooled-quarter source-market coverage;
4. Reddit monthly rank movement from #4 to #5 to #41;
5. a three-month source market containing 556 registrable cited domains;
6. explicit treatment of 218 technical or unusable citation entries;
7. category-overlap analysis showing only 32 shared domains with Perplexity's broader Top 100;
8. comparison with broad Perplexity research from Ahrefs;
9. comparison with Tinuiti's Q3 platform findings; and
10. explicit disclosure that the frozen parent sources do not publish a separate Perplexity balanced aggregate endpoint share.

The narrow research question is:

How stable was Reddit as a directly cited source in Perplexity for consequential health and medical consumer decisions from July through September 2026?

Why AI Citation Studies Can Disagree

Questions This Section Answers

• Why can broad Perplexity research rank Reddit first while this health study shows a steep September rank decline?
• Why can a three-month rank differ from a matched endpoint result?
• What should healthcare marketers compare before using an external benchmark?

Query population

Broad all-topic queries include many categories where Reddit may be used more frequently than in high-stakes health decisions.

Time period

The three-month source ranking pools July, August and September.

The strict matched test compares only July and September.

Denominator

Response citation coverage, citation-event share, monthly rank and external mention share answer different questions.

Category specialization

Health prompts surface specialists such as Healthline, NCOA, HearingTracker, GoodRx and SeniorLiving.org at rates that broad source leaderboards can miss.

Missing July data

Medical Alert Systems does not have a July source dataset, so it is excluded from the balanced parent endpoint rather than treated as zero.

Technical-source cleanup

The Perplexity health source study excludes 218 technical or unusable citation entries.

Prompt matching

The strict paired analysis requires the same normalized prompt and Perplexity platform family at both endpoints.

Small matched baseline

Only three matched Perplexity health scenarios cited Reddit in July.

That makes the 100% matched relative decline directionally meaningful but statistically weak.

Prompt weighting

The panel is not weighted by patient volume, healthcare spend, search volume, CPC, revenue, policy value or conversion probability.

The correct question is therefore not:

"What is Reddit's universal Perplexity health citation rate?"

The useful question is:

What did Reddit citation visibility look like for this platform, this health decision population, this time period and this measurement definition?

Methodology

Source archive

This study uses the frozen July-September 2026 LLM Authority Index High-Stakes Consumer Decisions corpus underlying the Health and Medical source studies and the parent health Reddit analysis.

Platform filter

Only observations assigned to the Perplexity platform family are used for the child platform analyses.

Category filter

Observations are included when their source membership belongs to the Health and Medical family.

Three-month Perplexity health source sample

The supporting source study reports:

• 918 raw July-September Perplexity health observations
• 0 explicit extraction failures
• 858 eligible deduplicated responses
• 2,367 captured citation entries before public-source filtering
• 218 technical or unusable exclusions
• 2,149 substantive public-facing citation events
• 556 registrable cited domains
• 1,981 domain-response appearances

Exact analytical repeat handling

Exact analytical repeats are controlled using the project's documented repeat rules so duplicate observations do not inflate source coverage.

Prompt normalization

Matched prompt text is normalized using Unicode NFKC normalization, case folding, whitespace collapse and trimming.

Domain normalization

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

Reddit identification

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

Public technical exclusions

The Perplexity health public ranking excludes:

• 171 thumbnail-CDN entries
• 33 st.perplexity.ai static-asset entries
• 13 Mapbox homepage/infrastructure entries
• 1 blank or unusable citation URL

Total excluded: 218.

Response citation coverage

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

For the three-month source market:

29 / 858 = 3.38%

Citation-event share

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

For the three-month source market:

30 / 2,149 ≈ 1.40%

Matched prompt-plus-platform test

The strict matched Perplexity panel contains 92 scenarios.

The contingency table is:

• both July and September cite Reddit: 0
• July cites Reddit, September does not: 3
• July does not cite Reddit, September cites Reddit: 0
• neither month cites Reddit: 89

Matched response coverage falls from:

3 / 92 = 3.2609%

to:

0 / 92 = 0.00%

The derived exact two-sided McNemar p-value is 0.25.

Aggregate endpoint availability

The frozen parent study does not publish separate Perplexity-specific balanced aggregate July and September event-share or response-coverage values.

Those values are therefore left unpublished in this child article rather than estimated from monthly rank.

Limitations

1. The strict matched Perplexity panel contains only three discordant Reddit-positive July cases.
2. The derived exact McNemar p-value does not cross a conventional 0.05 significance threshold.
3. The parent source does not publish a separate Perplexity aggregate balanced endpoint share, so this article does not report one.
4. The three-month source ranking pools July, August and September and should not be treated as a September-only visibility rate.
5. Visible citation does not prove recommendation causality, hidden retrieval influence or training-data use.
6. Medical Alert Systems does not have a July source file and is excluded from the balanced parent endpoint.
7. Domain-level aggregation hides page-level source differences.
8. Technical-source cleanup can make denominators differ from raw citation exports.
9. Perplexity behavior can vary by geography, personalization, model version, retrieval configuration and product rollout.
10. The all-platform replacement table should not be interpreted as a Perplexity-only replacement analysis.
11. External studies use different query populations, dates, markets, metrics and collection systems.
12. The study does not evaluate the medical quality or clinical reliability of Reddit content.

Commercial Disclosure

LLM Authority Index is affiliated with CiteWorks Studio and related AI-search research and services. This research documents observed AI citation behavior.

Commercial relationships do not alter the frozen source corpus, platform filter, category filter, matching contract 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 Perplexity.

References

1. LLM Authority Index: The 2026 AI Citation Authority Study
2. LLM Authority Index: The Most-Cited Websites in AI for High-Stakes Health and Medical Consumer Decisions
3. LLM Authority Index: Reddit's Decline in AI Citations for High-Stakes Health and Medical Consumer Decisions
4. LLM Authority Index: The 100 Most-Cited Websites in Perplexity for High-Stakes Health and Medical Consumer Decisions
5. LLM Authority Index: The Persistence-Portability Gap
6. LLM Authority Index: The 100 Most-Cited Websites in Perplexity for High-Stakes Consumer Decisions
7. Ahrefs: The 50 Most-Cited Websites in Perplexity, September 2026
8. Tinuiti: Q3 2026 AI Citation Trends Report
9. BrightEdge: Health and Finance Citation Authority Across ChatGPT and Google AI Overviews

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 Perplexity 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