Can adults grow new brain cells? Every human neurogenesis study scored

01 Key findings

1. Most studies say yes, in small numbers. 32 of 49 human studies report new neurons in adult brains (9 of them rare or declining); 10 found none; 7 are mixed.IQ Metrics ledger, 1998-2026
2. The hippocampus is where the debate is. 27 of 49 studies are about it; 21 report new neurons, 5 found none.IQ Metrics ledger
3. Carbon-14 draws a map. Bomb-pulse dating found new neurons in the hippocampus, striatum and amygdala, and none in the neocortex or olfactory bulb.Spalding, Ernst, Roeder, Bhardwaj, Bergmann, Huttner
4. The newest methods lean yes. 8 of 10 single-cell RNA studies (since 2022) report new or immature neurons in adults; one, Franjic 2022, found none.IQ Metrics ledger
5. The tissue question is mostly unreported. Only 6 of 49 studies state how long the brains waited before fixation.IQ Metrics ledger
6. Small samples. The 15 studies that state a sample examined 440 brains in all; 31 do not state one in the text we could read.IQ Metrics calculation

02 Statistics to quote

03 Can adults grow new brain cells?

Most human studies say yes, in small numbers: 32 of the 49 primary studies we found (1998-2026) report new neurons in adult brains, 9 of them describing the numbers as rare or falling with age, while 10 found none and 7 are mixed. Adult neurogenesis, the birth of new neurons after childhood, is well established in rodents ^[53]; in people it has been argued about for almost three decades because nobody can watch it happen in a living human brain. Every study works on tissue after death or surgery, with a marker or a dating method that is indirect in its own way.

We built our own ledger to count the answers. We searched Europe PMC eight ways for 1998-2026, added 15 named leads, read 101 abstracts by hand and kept 49 primary studies of adult human brain tissue that state a finding about new neurons in adults ^[1]. For each one we copied the authors’ own conclusion sentence, coded it with a rule we wrote before coding (found, rare or declining, not found, mixed), and checked the sentence by script against the saved abstract or full text. We never re-judged a study: a paper that said “very limited, if any” is coded as its authors wrote it.

Adult neurogenesis

The birth of new neurons in the brain after childhood, from stem or progenitor cells. In rodents it happens throughout life in the hippocampus and in the walls of the lateral ventricles ^[53].

Hippocampus and dentate gyrus

The hippocampus, in each temporal lobe, is essential for forming and retrieving memories ^[56]; its dentate gyrus is where adult-born neurons appear in rodents and where most human studies look.

Doublecortin (DCX)

A protein made by young, migrating neurons. Many human studies count DCX-stained cells as immature neurons; others show DCX in neurons that are not new ^{[34] [37]}.

BrdU (bromodeoxyuridine)

A molecule taken into the DNA of dividing cells. Cancer patients who had received BrdU during their treatment provided the first direct evidence of new neurons in adult humans ^[4].

Carbon-14 (bomb-pulse) dating

Nuclear weapons tests raised carbon-14 in the air until 1963, and the level in a cell’s DNA follows the air at the time the DNA was made. Measuring it dates when a group of neurons was born ^[7].

Single-nucleus RNA sequencing

Reads which genes are active in thousands of single cell nuclei from frozen tissue, so cell types, including young neurons, can be recognised by their gene profiles ^[40].

Post-mortem interval (fixation delay)

The time between death and preserving the tissue. Longer delays can weaken staining for markers such as DCX, one reason why studies disagree ^{[32] [55]}.

Immature neuron

A neuron that still carries young-neuron markers. It may be newly born, or, as in the amygdala and cortex, an old neuron that stays immature for decades ^[31].

04 How many studies have looked for new neurons in adult humans?

We count 49 primary human studies from 1998 to 2026 that looked for new neurons in the adult brain and state what they found: 46 with new tissue and 3 re-analyses of other groups’ data. They come from 509 unique records in our searches and leads, 329 of which passed a scripted title rule; we read 101 abstracts in full and left 52 out, mostly comments, letters and disease-only comparisons. The count is a lower bound: a study our searches did not find is not in it, and we list every record we read and dropped.

Figure 1

From 509 records to 49 primary studies: how we built the ledger

Stage 1: unique records from eight Europe PMC title searches (1998 to 2026) and 15 named leads. Stage 2: titles that name a neurogenesis object and are not animal- or culture-only. Stage 3: abstracts read by hand. Stage 4: primary studies of adult human brain tissue that state a finding about new neurons in adults. As of 6 November 2026.

Unique records from 8 Europe PMC searches + 15 named leads509all

Our scripted title rule (written before reading)

Passed the scripted title rule32964.6% of all

Picked by hand from the titles for a full read of the abstract

Abstract read by hand10119.8% of all

52 records left out after reading: 21 comments or letters, 6 disease comparisons only, cultures, protocols, stem-cell-only and other reasons (table at the end)

Primary adult human studies (the ledger)499.6% of all

3 re-analyses of other groups' data add no new brains

New tissue (not re-analyses)469.0% of all

Only 15 of 46 new-tissue studies state, in the text we could read, how many brains they examined

State how many brains152.9% of all

The studies cluster in time. The first decade gave a handful of papers, led by the 1998 BrdU study of Eriksson and colleagues ^[4]. Interest jumped in 2018, when two high-profile papers reached opposite conclusions in the same year: Sorrells and colleagues found no young neurons in adult hippocampi ^[28], and Boldrini and colleagues found “preserved neurogenesis” in healthy older people ^[26]. 27 of the 49 studies in our ledger appeared in 2018 or later.

Figure 2

49 human studies, 1998 to 2026, by brain region and what each found

Every study in the ledger by publication year and the brain region its conclusion is about; colour = the verdict coded from the authors' own sentence. 27 of the 49 are about the hippocampus. 27 studies appeared in 2018 or later. As of 6 November 2026.

Found in adultsRare or decliningMixed or unclearNot found

Hippocampus27 studiesEriksson 1998Knoth 2010Bayer 2015Kumar 2020

SVZ and olfactory path8 studiesWeickert 2000Quiñones-Hinojosa 2006Snapyan 2025

Olfactory bulb2 studiesBergmann 2012

Striatum2 studiesErnst 2014Herold 2025

Amygdala3 studiesMartí-Mengual 2013

Hypothalamus1 studyBatailler 2014

Neocortex and cortex6 studiesSpalding 2005Huttner 2014Li 2023

200020052010201520202025

The nearest existing synthesis is a 2024 systematic review of adult primates by Elliott and colleagues, which searched three databases to June 2023 and synthesised 112 papers on humans and other primates, including disease and imaging studies ^[54]. Our ledger is narrower and newer: human brain tissue only, one coded verdict per study in the authors’ words, the 10 studies published from 2024 on, and an open file that anyone can re-sort. The 2018 consensus review by Kempermann and co-authors sets out the open questions we track ^[53].

The balance has shifted with time. Before 2018, 14 of 22 studies reported new neurons in adults; from 2018 to 2021, 6 of 10; and since 2022, 12 of 17, with a single “not found” (Franjic 2022) ^[37]. Newer studies are not automatically better, but they use more brains, faster tissue handling or single-cell methods, and several were designed to answer the 2018 critique directly.

Figure 3

Since 2022, 12 of 17 new studies report new neurons in adults

Studies in the ledger by period of publication and verdict. 2018 is the year of the two opposing papers (Sorrells and Boldrini); 2022 the first single-nucleus RNA studies. Only one study since 2022 found no new neurons (Franjic 2022). As of 6 November 2026.

Found in adultsRare or decliningMixed or unclearNot found

9'98-'09

13'10-'17

10'18-'21

17'22-'26

05 Does the adult hippocampus grow new neurons?

Yes in most studies: 21 of 27 hippocampus studies report new neurons in adults, 7 of them as rare or declining, and 5 found none. The strongest single number is from carbon-14 dating: Spalding and colleagues estimate that “700 new neurons are added in each hippocampus per day”, an annual turnover of 1.75% within the third of neurons that renew, with “a modest decline during aging” ^[18]. The same paper concludes that the rates are comparable in middle-aged humans and mice.

The “found” side rests mostly on immunostaining. Boldrini and colleagues counted thousands of immature neurons in whole hippocampi from 28 people aged 14 to 79 who died suddenly, with post-mortem intervals of 4 to 26 hours ^[26]. Moreno-Jiménez and colleagues, using brain samples obtained under tightly controlled conditions, reported thousands of immature neurons in healthy people “up to the ninth decade of life” and fewer as Alzheimer’s disease advanced ^[29]. Tobin and colleagues found neuroblasts and immature neurons in 18 people aged 79 to 99 ^[32], and Dumitru and colleagues in Jonas Frisén’s group found proliferating neural progenitors in adults by single-nucleus RNA sequencing and Ki67 staining ^[46].

The “not found” side is smaller but cited heavily. Sorrells and colleagues examined 59 specimens and report that in adults aged 18 to 77 “young neurons were not detected in the dentate gyrus” ^[28]; their 2021 follow-up adds that DCX is also found in adult amygdala and cortex neurons that are not new ^[34]. Dennis and colleagues found that after age 3 the only dividing cells in the human neurogenic niches were microglia ^[24], Cipriani and colleagues judged the adult neurogenic potential “negligible” ^[27], and Franjic and colleagues found neurogenesis signatures in adult mice, pigs and macaques “but not humans” ^[37].

Figure 4

How old were the oldest brains? 10 studies state it

Age of the oldest donor each study examined, in years, with its verdict. Tobin et al. report neurogenesis "persistent through the tenth decade of life" in donors aged 79 to 99; Knoth et al. detected DCX up to 100 years but in exponentially falling numbers; Sorrells et al. found no young neurons in adults up to 77. As of 6 November 2026.

Knoth 2010 (rare)100

Li 2023 (mixed)100

Tobin 2019 (found)99

Zhou 2022 (found)92

Mathews 2017 (rare)88

Roeder 2022 (found)86

Boldrini 2018 (found)79

Sorrells 2018 (not found)77

Dennis 2016 (not found)59

Seki 2019 (rare)49

405060708090100

Between the two sides sit the “rare or declining” studies, 7 in the hippocampus. Knoth and colleagues traced DCX across 54 people from birth to 100 and found the number of DCX cells falling exponentially with age ^[13]; Mathews and colleagues found decreasing proliferation and immature-neuron gene expression across 26 adults aged 18 to 88 ^[25]; Seki and colleagues, with surgical tissue fixed at once, concluded that hippocampal neuron production in adults is low ^[30]; and Simard and colleagues found “very low levels” with spatial transcriptomics ^[44]. Our pages on memory and IQ and on how much the brain can store explain what the hippocampus does for memory.

06 Why do neurogenesis studies disagree?

Neurogenesis studies disagree mainly over markers and tissue: 16 of 27 immunostaining studies report new neurons, while carbon-14 dating, which reads a cell’s birth date from its DNA, splits cleanly by brain region. Immunostaining for DCX, PSA-NCAM or Ki67 depends on how fast tissue is fixed, which antibody is used and whether the marker is specific to new cells; the protocol paper of the Llorens-Martín group shows how slight changes in method flip results ^[55]. A marker study found DCX transcripts in both hippocampus and prefrontal cortex and concluded that such markers are not definitive indicators of adult neurogenesis ^[57].

Figure 5

Does the method decide the answer? Verdicts by the method behind each study

Number of studies per method (the family of the decisive evidence) and verdict. Carbon-14 dating splits by region: new neurons in the hippocampus, striatum and amygdala, none in the neocortex or olfactory bulb. Immunostaining (DCX, PSA-NCAM, Ki67) gives every kind of answer. As of 6 November 2026.

0 studies12 studies

FoundFRareRMixedMNoneNBrdU / IdU2000Carbon-143004Immunostaining12465Single-cell RNA5311Bulk RNA1200

Tissue handling is the variable both sides argue about, yet only 6 of the 49 studies state the longest delay between death and fixation for their samples. In those six, the one study that found no young neurons allowed up to 48 hours for autopsy samples ^[28], while studies that found them allowed 12 to 36 hours ^{[51] [26] [49]}, and two “rare” studies used fresh or surgical tissue ^{[30] [45]}. Six points cannot settle the question, and several papers that make the delay argument state it only in tables or paywalled methods we could not read.

Figure 6

Only 6 of 49 studies state how long their tissue waited: 0 to 48 hours

Longest post-mortem interval or time to fixation a paper states for its samples, in hours (surgical tissue fixed at once = 0). The study that found no young neurons allowed up to 48 hours; three that found them allowed 12 to 36. Six points cannot settle whether delay explains the split. As of 6 November 2026.

Seki 2019 (rare)0 h

Yao 2024 (rare)5 h

Disouky 2026 (found)12 h

Boldrini 2018 (found)26 h

Snapyan 2025 (found)36 h

Sorrells 2018 (not found)48 h

Single-cell methods did not end the argument. Single-nucleus RNA sequencing arrived in this field in 2022; 8 of the 10 single-cell studies report new or immature neurons in adults, and one, Franjic 2022, found none. Tosoni and colleagues re-analysed the published datasets in 2023 and argued that they “can be confounded by methodological, conceptual, and biological factors” ^[42]; Zhou and colleagues had reported immature granule cells across the lifespan in 2022 ^[40]; since the re-analysis, Dumitru and colleagues ^[46], Disouky and colleagues ^[51] and Tosoni and colleagues ^[52] have all reported neurogenic cells in adult hippocampi. The debate is a good example of why we track which famous brain findings hold up when retested.

07 Where in the adult brain do new neurons appear?

New neurons in adults are reported mainly in the hippocampus, the striatum and the amygdala, and not in the neocortex: all 6 neocortex and cortex studies in our ledger are “not found” or “mixed”. Carbon-14 dating showed that neurons of the adult neocortex are as old as the person ^{[7] [8]}, even after a stroke ^[21]. In the striatum, Ernst and colleagues found that “in adult humans new neurons integrate”, apparently interneurons only ^[20]; in the amygdala, Roeder and colleagues estimate an overall renewal rate of more than 2.7% a year ^[38].

Figure 7

Method, brain region, verdict: how 49 studies flow

Width = number of studies. Left: the method behind the decisive evidence. Middle: the region the conclusion is about ("Other" = striatum, hypothalamus, olfactory bulb). Right: the verdict in the authors' words. Every neocortex and cortex study is "not found" or "mixed"; the hippocampus gives every answer. As of 6 November 2026.

MethodMethodRegionRegionVerdictVerdict

BrdU / IdUBrdU 2Carbon-14C-14 7ImmunostainingStaining 27Single-cell RNAscRNA 10Bulk RNABulk RNA 3

HippocampusHippo. 27SVZ and olfactory pathwaySVZ 8AmygdalaAmygd. 3Neocortex and cortexCortex 6Other regionsOther 5

Found in adultsFound 23Rare or decliningRare 9Mixed or unclearMixed 7Not foundNone 10

The olfactory system, the second big source of new neurons in rodents, looks different in people. Neuroblasts are reported in the adult human subventricular zone and its migratory stream ^{[15] [11]}, but carbon-14 dating found “very limited, if any” new neurons in the adult olfactory bulb itself ^[16], and Sanai and colleagues found the infant migratory corridors “nearly extinct by adulthood” ^[14]; a large stream of young neurons into the frontal lobe is seen only in infants ^[58]. Immature-looking neurons in the adult amygdala and cortex are a separate case: Sorrells and colleagues read them as neurons that stay immature for decades rather than new ones ^[31], so we code those studies “mixed”.

08 How many human brains have been examined for new neurons?

At least 440 brains: that is the total in the 15 studies that state how many people they examined, in the text we could read. The other 31 new-tissue studies give no number in the text we could open (it may sit in supplementary tables or paywalled methods), so the true total is higher. Of the counted brains, 244 were in studies that found new neurons, 107 in “rare or declining” studies and 88 in studies that found none.

Figure 8

Every brain counted: 440 brains in the 15 studies that state how many they examined

One square = one person whose brain tissue a study examined (all ages, as the paper counts them), coloured by that study's verdict: 244 in studies that found new neurons, 107 rare or declining, 88 not found, 1 mixed. 31 of 46 new-tissue studies do not state the number in the text we could read, so this is a floor. IQ Metrics calculation. As of 6 November 2026.

Found in adults 244Rare or declining 107Mixed or unclear 1Not found 88

440 brainsone square = one brain

Samples are small for a question about the whole species. The largest study in our count, Zhou and colleagues, used 62 post-mortem specimens from fetal life to 92 years plus 10 surgical specimens ^[40]; Sorrells and colleagues used 59 ^[28]; Márquez-Valadez and colleagues 59, including 14 healthy controls ^[48]. Most studies examined a few dozen brains or fewer, and some include children and fetal tissue in the same count. Ages matter too: the oldest donors are in Tobin’s study (79 to 99) and Knoth’s (up to 100) ^{[32] [13]}.

Figure 9

Bigger samples came late: brains examined per study, by year

15 studies that state how many brains they examined, by publication year (across) and brains (up, log scale); bubble area = OpenAlex citations. The largest is Zhou 2022 (72 specimens, fetal to 92 years); the smallest examined one human brain. As of 6 November 2026.

Found in adultsRare or decliningMixed or unclearNot found

Citations (OpenAlex)505001,500

Brains examined (log scale)

110100

Sorrells 2018Boldrini 2018Knoth 2010Tobin 2019Franjic 2022Zhou 2022Dennis 2016Seki 2019Cao 2024Roeder 2022Márquez-Valadez 2025Yao 2024Snapyan 2025Herold 2025

2010201520202025

Publication year

09 Which neurogenesis studies are cited most?

The 1998 study by Eriksson and colleagues is the most cited, with 6,330 citations in OpenAlex on 6 November 2026, followed by Spalding 2013 (1,825), Moreno-Jiménez 2019 (1,550) and Sorrells 2018 (1,407) ^[2]. Of the 26 hippocampus studies published after Eriksson’s, 20 report new neurons in adults and 5 found none, so the most-cited claim is supported by most, not all, later work.

Figure 10

The 1998 study still leads with 6,330 citations; all 49 studies by year and citations

Each dot is one study: publication year (across) and OpenAlex citations on 6 November 2026 (up, log scale), coloured by verdict. Newer papers have had less time to be cited. The four most cited: Eriksson 1998 (6,330); Spalding 2013 (1,825); Moreno-Jiménez 2019 (1,550); Sorrells 2018 (1,407). As of 6 November 2026.

Found in adultsRare or decliningMixed or unclearNot found

Citations (OpenAlex, log scale)

1101001k10k

Eriksson 1998Weickert 2000Sanai 2004Spalding 2005Bhardwaj 2006Baer 2007Curtis 2007Liu 2008Knoth 2010Wang 2011Bergmann 2012Spalding 2013Huttner 2014Lötsch 2014Sorrells 2018Moreno-Jiménez 2019Tobin 2019Kumar 2020Franjic 2022Roeder 2022Wang 2022Zhou 2022Cao 2024Dumitru 2025Herold 2025Snapyan 2025Zhou 2025Disouky 2026Tosoni 2026

200020052010201520202025

Publication year

Per year since publication, “not found” papers are cited more than “found” papers (median 24.4 against 19.3 a year, our calculation). That does not mean they are more right. The “not found” group holds the 2018 Nature paper that started the current debate, and a paper that starts a debate is cited by both sides. Citation counts measure attention, not truth; we show them because press and search engines lean on the most-cited claim.

Figure 11

Are "not found" papers cited more? Citations per year, by verdict

OpenAlex citations divided by years since publication (counting the publication year), one dot per study. Median: 19.3 a year for "found", 24.4 for "not found". Box = middle half, whiskers = lowest and highest study. A citation is not an endorsement: critics cite a paper too. IQ Metrics calculation. As of 6 November 2026.

Middle halfMedianWhiskerscitations a year

Found in adults23 studies19.3

Rare or declining9 studies12.3

Mixed or unclear7 studies5.8

Not found10 studies24.4

050100150200250

Citations per year since publication (OpenAlex).

10 How many brain cells do you lose a day?

No study counts brain cells lost per day; the often-quoted figure is arithmetic on cross-sectional counts. Pakkenberg and Gundersen counted neocortical neurons in 94 Danish brains aged 20 to 90: about 19 billion in women and 23 billion in men, with “approximately 10% of all neocortical neurons” lost over the life span ^[59]. Spread evenly over those 70 years, that is about 74,000 to 90,000 neocortical neurons a day (IQ Metrics calculation), an average, not a measured daily loss.

The two numbers measure different things and should not be subtracted: the loss is across the whole neocortex, where carbon-14 found no adult-born neurons at all ^[8], while the 700 a day are added in the hippocampus alone ^[18]. How thinking changes across adult life is a separate question: our studies of peak brain age and IQ and age show which abilities change and when, and are human brains shrinking looks at brain size over a much longer time.

11 Do other animals grow new neurons as adults?

Many mammals do, but not all. Franjic and colleagues found clear signatures of adult hippocampal neurogenesis in mice, pigs and macaques with the same single-nucleus method that found none in humans ^[37]; in rhesus monkeys, Sorrells and colleagues saw hippocampal neurogenesis diminish during juvenile development ^[28]. Patzke and colleagues examined 71 mammal species and found that whales, dolphins and porpoises show “no clear signs of adult hippocampal neurogenesis” ^[56]. Our connectome study shows how much of these brains has been mapped cell by cell.

• Mouse, pig, macaque (adults): neurogenesis signatures found ^[37]
• Rhesus monkey: high in infancy, diminishing in juveniles ^[28]
• Whales, dolphins, porpoises: no DCX staining in the dentate gyrus ^[56]
• Humans: 21 of 27 hippocampus studies report new neurons in adults (this ledger)

12 What does this mean, and what does it not show?

The ledger shows what researchers concluded, not whether new neurons matter for thinking. A few studies link neuroblast numbers to better memory in old age or to cognitive resilience ^{[32] [51] [52]}, but these are links in small post-mortem samples, not causes. We found no primary human study in our ledger that tested whether exercise, diet or brain training grows new neurons in people; such claims rest on animal work. Our news story on whether brain-training apps work and the study on languages and brain ageing cover what has been tested in people.

Two cautions apply to every number here. First, the verdicts are the authors’ readings of their own data, coded without re-judging; a “found” study using DCX staining and a “not found” study using the same marker may disagree about what the marker means. Second, disease-focused studies (Alzheimer’s, epilepsy, Parkinson’s, addiction) are kept only when they also state a finding about adults in general or their healthy controls. The brain statistics fact check traces other popular brain numbers to their sources, and the memory game is a quick way to test the memory the hippocampus supports.

13 Every human neurogenesis study in our ledger

Table 1

Every study in our ledger (49 rows)

Oldest first. Brains = people whose tissue the paper examined, all ages, as stated; "-" = not stated in the text we could read. Ages = adult donors (or the oldest donor). The verdict is coded from the sentence quoted, the authors' own words. The CSV adds journal, DOI, tissue, delay, citations and licence. As of 6 November 2026.

Study	Year	Region	Method	Brains	Ages	Verdict	In the authors' words	Disease focus
Eriksson 1998 [4]	1998	Hippocampus	BrdU / IdU	–	–	Found in adults	“we demonstrate that new neurons, as defined by these markers, are generated from dividing progenitor cells in the dentate gyrus of adult humans”	Cancer patients given BrdU during treatment
Weickert 2000 [5]	2000	SVZ and olfactory pathway	Immunostaining	–	–	Found in adults	“Our results show that neuroblast-like cells exist in the human SEZ and support the theory that SEZ of postnatal human brain has neurogenic potential”	–
Sanai 2004 [6]	2004	SVZ and olfactory pathway	Immunostaining	–	–	Not found	“Unexpectedly, we find no evidence of chains of migrating neuroblasts in the SVZ or in the pathway to the olfactory bulb”	–
Spalding 2005 [7]	2005	Neocortex	Carbon-14	–	–	Not found	“occipital neurons are as old as the individual, supporting the view that postnatal neurogenesis does not take place in this region”	–
Bhardwaj 2006 [8]	2006	Neocortex	Carbon-14	–	–	Not found	“neurons in the human cerebral neocortex are not generated in adulthood at detectable levels but are generated perinatally”	Also patients given BrdU
Quiñones-Hinojosa 2006 [9]	2006	SVZ and olfactory pathway	Immunostaining	–	–	Rare or declining	“However, compared to rodents, the adult human SVZ appears to be devoid of chain migration or large numbers of newly formed young neurons”	–
Baer 2007 [10]	2007	SVZ and olfactory pathway	Immunostaining	–	–	Found in adults	“Thus, our data surprisingly reveal that these TFs are differentially expressed in the adult human SVZ where Sox-2 and Pax-6 specify a glial and neuronal fate, respectively”	–
Curtis 2007 [11]	2007	SVZ and olfactory pathway	BrdU / IdU	–	–	Found in adults	“contains progenitor cells with migratory characteristics and cells that incorporate 5-bromo-2′-deoxyuridine and become mature neurons in the OB”	–
Liu 2008 [12]	2008	Cortex	Immunostaining	–	–	Mixed or unclear	“cells expressing doublecortin (Dcx), a microtubule-associated protein expressed in migrating neuroblasts, were present in the hippocampus and temporal cortex of the normal and MTLE adult human brain”	Temporal lobe epilepsy
Knoth 2010 [13]	2010	Hippocampus	Immunostaining	54	up to 100	Rare or declining	“Total numbers of DCX expressing cells declined exponentially with increasing age, and co-expression of DCX with the other markers decreased”	–
Sanai 2011 [14]	2011	SVZ and olfactory pathway	Immunostaining	–	–	Rare or declining	“this germinal activity subsides in older children and is nearly extinct by adulthood”	–
Wang 2011 [15]	2011	SVZ and olfactory pathway	Immunostaining	–	–	Found in adults	“We provide evidence that neuroblasts exist continuously in the anterior ventral SVZ and RMS of the adult human brain”	–
Bergmann 2012 [16]	2012	Olfactory bulb	Carbon-14	–	–	Not found	“establishing that there is very limited, if any, postnatal neurogenesis in the human olfactory bulb”	–
Martí-Mengual 2013 [17]	2013	Amygdala	Immunostaining	–	–	Mixed or unclear	“Our results demonstrate that cells coexpressing doublecortin and PSA-NCAM, but lacking neuronal nuclear antigen expression, were present in the amygdala of adult humans”	–
Spalding 2013 [18]	2013	Hippocampus	Carbon-14	–	–	Found in adults	“In adult humans, 700 new neurons are added in each hippocampus per day, corresponding to an annual turnover of 1.75% of the neurons within the renewing fraction, with a modest decline during aging”	–
Batailler 2014 [19]	2014	Hypothalamus	Immunostaining	–	–	Found in adults	“This study provides further confirmation of the existence of an adult hypothalamic neurogenic niche and argues for the potential existence of a migratory path within the hypothalamus”	–
Ernst 2014 [20]	2014	Striatum	Carbon-14	–	–	Found in adults	“We show, using histological and carbon-14 dating approaches, that in adult humans new neurons integrate in the striatum, which is adjacent to this neurogenic niche”	Also Huntington’s disease
Huttner 2014 [21]	2014	Neocortex	Carbon-14	–	–	Not found	“Using immunohistochemistry; transcriptome, genome and ploidy analyses; and determination of nuclear bomb test-derived (14)C concentration in neuronal DNA, we found neither to be the case”	Stroke
Lötsch 2014 [22]	2014	Olfactory bulb	Bulk RNA	–	–	Found in adults	“This provides a novel, functional genomics perspective supporting the existence of neurogenesis in the adult human olfactory bulb”	–
Bayer 2015 [23]	2015	Hippocampus	Immunostaining	–	–	Found in adults	“The age-dependent increase of differentiating cells in the healthy controls was not observed in the addicts”	Heroin addiction
Dennis 2016 [24]	2016	Hippocampus	Immunostaining	23	up to 59	Not found	“However, after 3 years of age, microglia were the only proliferating cells found in either niche or in the adjacent parenchyma”	–
Mathews 2017 [25]	2017	Hippocampus	Bulk RNA	26	18-88	Rare or declining	“These data are the first to demonstrate normal age-related decreases at specific stages of adult human hippocampal neurogenesis”	–
Boldrini 2018 [26]	2018	Hippocampus	Immunostaining	28	up to 79	Found in adults	“Thus, healthy older subjects without cognitive impairment, neuropsychiatric disease, or treatment display preserved neurogenesis”	–
Cipriani 2018 [27]	2018	Hippocampus	Immunostaining	–	–	Not found	“while their neurogenic potential seems negligible in the adult”	Also Alzheimer’s disease
Sorrells 2018 [28]	2018	Hippocampus	Immunostaining	59	18-77	Not found	“In adult patients with epilepsy and healthy adults (18-77 years; n = 17 post-mortem samples from controls; n = 12 surgical resection samples from patients with epilepsy), young neurons were not detected in the dentate gyrus”	Also epilepsy (surgical samples)
Moreno-Jiménez 2019 [29]	2019	Hippocampus	Immunostaining	–	–	Found in adults	“we identified thousands of immature neurons in the DG of neurologically healthy human subjects up to the ninth decade of life”	Also Alzheimer’s disease
Seki 2019 [30]	2019	Hippocampus	Immunostaining	17	up to 49	Rare or declining	“The large number of PSA-NCAM+ cells and few DCX+/HuB+/Ki-67+ cells observed in the controls suggest that immature-type neurons are not recently generated neurons, and that the level of hippocampal neuronal production in adult humans is low”	Epilepsy (controls: other temporal surgery)
Sorrells 2019 [31]	2019	Amygdala	Immunostaining	–	–	Mixed or unclear	“Immature PL neurons persist into old age, yet local progenitor proliferation sharply decreases in infants”	–
Tobin 2019 [32]	2019	Hippocampus	Immunostaining	18	79-99	Found in adults	“Here, we demonstrate that hippocampal neurogenesis is persistent through the tenth decade of life and is detectable in patients with mild cognitive impairments and Alzheimer’s disease”	Also MCI and Alzheimer’s disease
Kumar 2020 [33]	2020	Hippocampus	Bulk RNA (re-analysis)	–	–	Rare or declining	“Our findings indicate that the progression of neurogenesis from progenitor cells is highly restricted in the human brain from childhood onwards”	–
Sorrells 2021 [34]	2021	Hippocampus	Immunostaining	–	–	Not found	“Analysis of available RNA-sequencing datasets supports the view that DG neurogenesis is rare or absent in the adult human brain”	–
Terreros-Roncal 2021 [35]	2021	Hippocampus	Immunostaining	–	–	Found in adults	“We found that adult-born dentate granule cells showed abnormal morphological development and changes in the expression of differentiation markers”	ALS, Huntington’s, Parkinson’s, Lewy body and frontotemporal dementia
Coviello 2022 [36]	2022	Cortex	Immunostaining	–	–	Mixed or unclear	“Our findings confirm the presence of immature neurons in several regions of the cerebral cortex of humans of different ages and define their lineage”	Epilepsy surgery; psychiatric brain bank
Franjic 2022 [37]	2022	Hippocampus	Single-cell RNA	6	–	Not found	“Integrated cross-species analysis revealed robust transcriptomic and histologic signatures of neurogenesis in the adult mouse, pig, and macaque but not humans”	–
Roeder 2022 [38]	2022	Amygdala	Carbon-14	12	44-86	Found in adults	“In conclusion, we provide evidence for postnatal neurogenesis in the human amygdala with cell turnover rates comparable to the hippocampus”	–
Wang 2022 [39]	2022	Hippocampus	Single-cell RNA	–	–	Rare or declining	“the proinflammatory status of astrocytes probably contributes to the decrease and variability of AHN in adults and elderly individuals”	–
Zhou 2022 [40]	2022	Hippocampus	Single-cell RNA	72	up to 92	Found in adults	“Together, our findings suggest the presence of a substantial number of imGCs in the adult human hippocampus via low-frequency de novo generation and protracted maturation”	Also Alzheimer’s disease
Li 2023 [41]	2023	Cortex	Immunostaining	–	up to 100	Mixed or unclear	“while both layer II and amygdalar DCX + neurons persist in the temporal lobe lifelong”	–
Tosoni 2023 [42]	2023	Hippocampus	Single-cell RNA (re-analysis)	–	–	Mixed or unclear	“We argue that, although promising, the single-cell transcriptomic profiling of AHN in the human brain can be confounded by methodological, conceptual, and biological factors”	–
Cao 2024 [43]	2024	Hippocampus	Immunostaining	30	–	Found in adults	“In this study, we observed a significant presence of neurogenic cells in the hippocampus’s dentate gyrus (DG) region in 30 individuals”	Also Alzheimer’s disease
Simard 2024 [44]	2024	Hippocampus	Single-cell RNA	–	–	Rare or declining	“Our findings indicate very low levels of hippocampal neurogenesis throughout life and the existence of a local reserve of plasticity in the adult human hippocampus”	–
Yao 2024 [45]	2024	Hippocampus	Single-cell RNA	10	–	Rare or declining	“help to explain why adult hippocampal neurogenesis is infrequently observed in humans”	Also stroke
Dumitru 2025 [46]	2025	Hippocampus	Single-cell RNA	–	–	Found in adults	“In adults, using antibodies against the proliferation marker Ki67 and machine learning algorithms, we found proliferating neural progenitor cells”	–
Herold 2025 [47]	2025	Striatum	Immunostaining	1	–	Mixed or unclear	“Additionally, signs of persistent neuronal plasticity were observed with Doublecortin+ cells in the human caudate nucleus but not in the macaque”	–
Márquez-Valadez 2025 [48]	2025	Hippocampus	Immunostaining	59	–	Found in adults	“modulate both AHN and the cells that compose the niche, not only in patients with these disorders but also in neurologically healthy control individuals”	Depression, schizophrenia, bipolar disorder
Snapyan 2025 [49]	2025	SVZ and olfactory pathway	Immunostaining	25	–	Found in adults	“Overall, our data indicate that long-term deep brain stimulation of the subthalamic nucleus promotes cell proliferation and neurogenesis in the subventricular zone that are reduced in Parkinson’s disease”	Huntington’s, Parkinson’s, deep brain stimulation
Zhou 2025 [50]	2025	Hippocampus	Single-cell RNA (re-analysis)	–	–	Found in adults	“We further identified human-specific transcriptomic features of imGCs”	–
Disouky 2026 [51]	2026	Hippocampus	Single-cell RNA	–	–	Found in adults	“we analysed the profiles of 355,997 nuclei isolated from the hippocampus samples and identified neural stem cells, neuroblasts and immature granule neurons”	Also preclinical and clinical Alzheimer’s disease
Tosoni 2026 [52]	2026	Hippocampus	Single-cell RNA	–	–	Found in adults	“we identified persistent populations of immature neurons across all donor groups”	Also Alzheimer’s disease and resilience

Table 2

Records we read and left out (52) and why

Reasons follow the inclusion rules in our coding file (I1 to I3). Leaving a paper out says nothing about its quality; reviews and comments are context, not studies.

First author and year	Reason
Ayhan 2021	no stated finding: single-nucleus atlas of epilepsy surgery tissue; neither abstract nor text states a result on adult neurogenesis
Cao 2026	comment: research highlight on Dumitru et al. 2025
Le Maître 2018	disease comparison only: alcohol abuse vs controls, no statement about the control adults
Monje 2007	disease comparison only: cancer treatment
Sgubin 2007	disease comparison only: subarachnoid hemorrhage (surgical samples)
Engel 2011	disease comparison only: epilepsy vs autopsy controls, Western blot
Paradisi 2010	culture: neurosphere assay of epilepsy surgery tissue
Bayat 2022	disease comparison only: COVID-19
Murray 2016	no stated finding: PSA-NCAM distribution as plasticity, no neurogenesis statement
Murray 2018	no stated finding: PSA-NCAM interneurons, no neurogenesis statement
Pellegrino 2018	stem-cell markers only: hypothalamic NPC marker profile
Baig 2024	stem-cell markers only: SVZ stem-cell atlas
Ghibaudi 2023	marker method study: antibody detection across species
Cho 2024	marker method study: DCX transcript breadth (context)
Flor-García 2020	protocol (context)
Gallardo-Caballero 2026	protocol
Paredes 2016	no adult donor: infant frontal lobe (context)
Oladimeji 2013	thesis
Wiseman 2022	comment
Gage 2025	comment
Gage 2025	comment
Lee 2018	comment
Nogueira 2018	letter
Arellano 2018	comment
Lima 2019	comment
Kheirbek 2013	comment
Kempermann 2014	comment
Macklis 2012	comment
Sanai 2007	comment
Alvarez-Buylla 2022	comment
Arellano 2022	comment
Terreros-Roncal 2022	comment (authors’ response)
Terreros-Roncal 2022	comment (authors’ response)
Dennis 2017	comment (authors’ response)
Marucci 2017	comment
Liu 2022	comment
Tartt 2018	comment (perspective)
Terstege 2022	comment (perspective)
Johansson 1999	culture
Pagano 2000	culture
Roy 2000	culture
Mezey 2003	transplanted cells (bone marrow)
Déry 2013	behavioural proxy
Déry 2015	behavioural proxy
Charvet 2018	modelling of other species’ data, no tissue
Korr 1999	no adult donor: developing cortex
Yang 2014	no adult donor: prenatal
Durante 2020	olfactory epithelium (outside the brain)
Hahn 2005	olfactory epithelium (outside the brain)
Song 2026	olfactory epithelium (outside the brain)
Altuna 2019	disease comparison only: DNA methylation in Alzheimer’s disease
Zaben 2021	culture: epileptic hippocampus progenitors

14 How we built the dataset

1. 01

   Search

   Eight title searches in Europe PMC for 1998-2026 (neurogenesis and human hippocampus; DCX; new or immature neurons; other regions; carbon-14 dating; transcriptomics; human tissue in the abstract; region markers), plus 15 named leads by DOI or title: 509 unique records. Preprints excluded.

2. 02

   Screen

   A scripted title rule kept 329 records; we read 101 abstracts by hand and kept 49 studies that pass three written rules: primary research, adult human brain tissue examined directly, and a stated finding about new neurons in adults.

3. 03

   Read and code

   For each study we copied the authors’ conclusion sentence and coded it found, rare or declining, not found or mixed (rules written before coding). Sample sizes, ages and tissue delays were typed only where stated, each with a check string. 23 full texts came from PubMed Central ^[3]; the rest from abstracts.

4. 04

   Check

   A script found every quoted sentence and every typed number (81 checks) in the saved abstract or full text; OpenAlex flags no retraction among the 49 studies ^[2].

5. 05

   Compute

   Counts by verdict, method, region and period; brains examined; citations per year. All IQ Metrics calculations, scripted from the cached files.