Cognitive Peptides: Semax, Selank, Dihexa and the Evidence

Disclaimer: This content is for educational purposes only and is not medical advice. Nothing on this page is intended to diagnose, treat, cure, or prevent any disease. Always consult a licensed healthcare provider before starting any peptide protocol, especially if you have a medical condition, take prescription medications, or are pregnant or nursing.

Overview

Cognitive and nootropic peptides are a category of short-chain bioactive molecules that researchers have explored for their potential effects on focus, learning, memory, mood regulation, and neuroprotection. Unlike classic stimulants such as caffeine, modafinil, or amphetamines — which primarily push monoamine release or block reuptake — many of the best-studied nootropic peptides appear to act upstream of neurotransmission, influencing growth factors like BDNF, modulating the melanocortin and GABAergic systems, or providing precursor amino acids that support synaptic function.

For NYC professionals, students, founders, and athletes seeking a sharper edge without the comedown profile of stimulants, peptides have become an increasingly visible alternative. They are not, however, a magic bullet. Effects are often subtle, cumulative, and highly individual. Most of the human data in this category comes from Russian and Eastern European clinical research — for example a 110-patient study of Semax in post-stroke rehabilitation (PMID 29798983) and a 62-patient comparison of Selank against the benzodiazepine medazepam (PMID 18454096). Those are real trials, but they are small, largely single-country, and rarely replicated. Where an independent group has reviewed a compound in this family — Cochrane's review of Cerebrolysin — it graded the evidence very low quality (PMID 31710397).

This hub provides a science-forward, hype-controlled overview of the most discussed cognitive peptides, their proposed mechanisms, how they compare to other nootropics, and what the realistic picture looks like for someone curious about adding them to a cognitive optimization protocol. If this is your first look at the category, Peptide 101: what are peptides? covers the vocabulary and the beginner library collects the rest of the start-here reading.

What Cognitive Peptides Aim To Do

• Focus and attention — sustained concentration, reduced mental fatigue
• Learning and memory consolidation — encoding and recall, especially under stress
• Mood regulation — anxiolysis without sedation, antidepressant-like effects
• Neuroprotection — protecting neurons from oxidative stress, ischemia, or aging
• Synaptic plasticity — the cellular substrate for learning and adaptation
• Recovery from injury — post-TBI, post-stroke, post-COVID cognitive issues

Why They've Become Popular Alternatives to Stimulants

• No documented dependence or withdrawal profile (for Semax/Selank specifically)
• No classic "crash" or rebound fatigue
• Generally do not interfere with sleep architecture
• Mechanisms targeting growth factors rather than acute neurotransmitter dumps
• Subtle, "cleaner" subjective profile compared to amphetamine-class stimulants
• Some compounds (Cerebrolysin) have decades of clinical use abroad

The Cognitive Peptide Families

Cognitive peptides fall into several distinct families, each with different origins, mechanisms, and evidence bases.

The Russian neuropeptide family — particularly Semax and Selank — has received the most attention in the Western biohacking community, largely because they are short, well-characterized, and have decades of regulatory approval in Russia for clinical indications like stroke recovery, anxiety disorders, and ADHD.

Semax — The Russian Focus Peptide

Semax is a synthetic heptapeptide developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. It is structurally derived from the 4-10 fragment of adrenocorticotropic hormone (ACTH), but with modifications that remove its hormonal activity while preserving (and amplifying) its central nervous system effects.

Structure and Mechanism

• Sequence: Met-Glu-His-Phe-Pro-Gly-Pro (an ACTH 4-7 analog with a C-terminal Pro-Gly-Pro extension)
• Half-life extension: The Pro-Gly-Pro tail increases stability against enzymatic degradation, allowing CNS exposure via intranasal administration. In vitro, tritium-labelled Semax bound specifically and reversibly to membranes isolated from rat basal forebrain; separately, intranasally dosed Semax raised BDNF protein in that region within three hours (PMID 16635254)
• BDNF/trkB upregulation: In rats, a single 50 µg/kg dose of Semax raised hippocampal BDNF protein about 1.4-fold and trkB receptor phosphorylation about 1.6-fold, alongside improved performance on a conditioned avoidance task (PMID 16996037). This is animal work — no equivalent human mechanistic study has been published
• Melanocortin pathway: Acts on melanocortin receptors, contributing to its attention and cognitive effects
• Dopaminergic modulation: May influence dopamine turnover, which is one proposed mechanism behind its use in ADHD-like presentations in Russian clinical practice

Russian Clinical Use

In Russia, Semax is approved for indications including ischemic stroke, transient ischemic attacks, encephalopathy, and certain attention-related conditions in children. It is administered intranasally as drops. The largest published clinical report followed 110 patients through post-stroke rehabilitation; those given Semax (two 10-day courses, 6,000 mcg/day) showed higher plasma BDNF and faster Barthel Index recovery than those who were not (PMID 29798983). The abstract does not describe blinding or a placebo arm, so read it as supportive rather than definitive. This regulatory approval does not exist in the United States, where Semax is sold only as a research chemical — the dated US position is on our tracker as Semax.

Common Subjective Effects (Anecdotal)

• Increased focus and sustained attention, typically felt within 30-60 minutes
• Reduced mental fatigue under cognitive load
• Cleaner alertness compared to caffeine — without jitteriness
• Mild mood elevation in some users
• Effects on a single dose tend to last 4-6 hours

For a deep dive on the N-Acetyl variant (the more stable form most commonly used today), see our NA-Semax + NA-Selank Protocol Guide and the standalone Semax Amidate Protocol for the further-modified variant.

Selank — Anxiolysis Without Sedation

Selank is Semax's sister peptide — same lab, same era, completely different mechanism and clinical use case. Where Semax targets focus and cognition, Selank targets anxiety and emotional regulation.

Structure and Mechanism

• Sequence: Thr-Lys-Pro-Arg-Pro-Gly-Pro (a tuftsin analog with the same Pro-Gly-Pro stabilizing tail)
• Origin: Derived from tuftsin, a naturally occurring immunomodulatory tetrapeptide
• GABA modulation: Research suggests Selank influences GABAergic transmission, but not via direct receptor binding — distinguishing it from benzodiazepines
• BDNF-linked effects: In rats, Selank prevented ethanol-induced memory and attention deficits and altered BDNF content in the hippocampus and frontal cortex, which the authors read as a neurotrophin-mediated mechanism (PMID 31625062)
• Serotonergic effects: May modulate serotonin metabolism, contributing to its mood-stabilizing profile

Distinct from Benzodiazepines

This is the critical clinical contrast. Benzodiazepines provide anxiolysis through direct GABA-A receptor potentiation, with side effects including sedation, cognitive impairment, tolerance, and physical dependence. Selank, in available research, does not appear to:

• Cause sedation
• Impair memory or cognitive performance
• Produce tolerance with repeated use
• Generate withdrawal syndrome on discontinuation

The clearest human comparison is a 62-patient Russian study in generalized anxiety disorder and neurasthenia: Selank's anxiolytic effect was similar to that of the benzodiazepine medazepam, with an additional anti-asthenic and mildly activating effect (PMID 18454096). That is one small comparative trial, not a body of evidence — there are no large, independently replicated Western trials of Selank. Its US regulatory position is tracked, with dates and sources, as Selank.

Common Subjective Effects (Anecdotal)

• Reduced anxiety without flattening or sedation
• Improved sleep quality (despite not being sedating during the day)
• Mild mood elevation
• Better stress tolerance under acute pressure

NA-Semax + NA-Selank: The Stack

The most discussed cognitive peptide stack in 2025-2026 combines N-Acetyl Semax with N-Acetyl Selank. The N-acetylated forms are further modified for stability and are generally considered more potent per microgram than the unmodified parent peptides.

Why the Stack Works (Theoretically)

Semax provides the upregulating, focus-promoting input. Selank provides the calming, anti-anxiety counterweight. The combination — sometimes described as "calm focus" — aims to reproduce the subjective profile that L-theanine + caffeine attempts at a much smaller scale, but with longer duration and a different mechanistic substrate.

How People Typically Run It

Both peptides are usually delivered intranasally, one to two sprays per nostril from a measured spray bottle reconstituted with sterile saline or bacteriostatic water. Semax is normally taken in the morning; Selank is taken either alongside it or later in the day, and is run continuously by some users and only as needed by others. Almost everyone runs it in blocks of a few weeks with a washout before reassessing.

Deliberately, no microgram figures appear here. There is no published human dose-response study for the N-acetyl variants, so a dosing table on a hub page would be false precision dressed up as guidance. The amounts people actually use — and what they are extrapolated from — belong in the protocol guides, which carry their own references: the Cognitive Peptide Stack Guide, the NA-Semax + NA-Selank Protocol Guide, and the Semax Amidate Protocol. Dosing decisions belong with a clinician, not a hub page.

Dihexa — The Potent c-Met Activator

Dihexa is in a completely different category from the Russian peptides. It is an oral hexapeptide derived from angiotensin IV, developed at Washington State University and originally explored for Alzheimer's disease research.

Mechanism

• HGF mimetic: Dihexa appears to mimic hepatocyte growth factor (HGF) at the c-Met receptor
• Synaptogenesis claims: The widely repeated line that Dihexa is "seven orders of magnitude more potent than BDNF" traces back to a small preclinical literature, not to human data — and, as below, its foundational paper has since been retracted
• Oral bioavailability: Unlike most peptides, Dihexa is reported to be orally active and BBB-penetrant

The Foundational Paper Was Retracted

The 2014 study that established Dihexa's proposed mechanism — that its procognitive and synaptogenic effects depend on HGF/c-Met activation — appeared in the Journal of Pharmacology and Experimental Therapeutics (PMID 25187433). That journal issued a Notice of Concern about it in 2021 and formally retracted it in April 2025 (PMID 40312093).

A retraction does not prove Dihexa does nothing. It does mean the single most-cited mechanistic result behind almost every Dihexa vendor page is no longer part of the scientific record — and anyone repeating the synaptogenesis numbers should say so.

Important Safety Caveat

The c-Met pathway has a well-established role in oncogenesis. Dysregulation of c-Met signaling is implicated in multiple cancer types, and HGF/c-Met is an active target of cancer therapeutics — drugs designed to block this pathway in patients with malignancy. High-level MET amplification and activating MET mutations and fusions are recognised oncogenic drivers, and MET inhibitors are in clinical development against them (PMID 32514147). Activating c-Met systemically, especially chronically, in humans therefore carries a theoretical oncogenic concern that no long-term human safety data resolves.

There are no published long-term human safety studies on Dihexa. Anyone considering it should:

• Understand this is preclinical research with no human safety profile
• Avoid use entirely if there is any personal or family history of cancer
• Limit cycles to short durations if used at all
• Discuss with a knowledgeable physician

For the full mechanistic breakdown, the synaptogenesis evidence, and a thorough discussion of the safety considerations, see the Dihexa Protocol Guide. Its FDA position is a dated row on our tracker as Dihexa.

Cerebrolysin — The Brain Extract

Cerebrolysin is the most clinically substantiated compound in this entire hub. It is not a single peptide — it is a multi-peptide preparation derived from enzymatically hydrolyzed porcine brain proteins.

What It Is

• A standardized mixture of low-molecular-weight peptides and free amino acids
• Manufactured by EVER Pharma (Austria), produced under pharmaceutical conditions
• Approved and used clinically in Russia, China, parts of Europe, and Latin America

Real Clinical Use

Unlike most peptides in this hub, Cerebrolysin has been studied in numerous randomized controlled trials, including for:

• Ischemic stroke recovery
• Vascular dementia
• Alzheimer's disease
• Traumatic brain injury
• Pediatric developmental conditions (in some countries)

The clinical data is more substantial than for any other compound discussed here — and still weak in absolute terms. The 2019 Cochrane review included six randomised trials (597 participants) in vascular dementia. Pooling three of them (420 participants) it found a benefit on cognition, and pooling two (379 participants) a benefit on global function, with no difference in adverse-event rates — but it graded the evidence very low quality, judged the included papers to carry a high risk of bias, noted that industry funding was reported for three of the six trials, and concluded that any real effect "may be too small to be clinically meaningful" (PMID 31710397). An independent 2021 systematic review of animal-derived nootropics reached the same verdict: possible benefit, modest effect sizes, low-to-very-low certainty (PMID 36324709).

Practical Notes

• Administered intramuscularly or intravenously (not nasal, not subcutaneous in standard practice)
• Typically used in intensive "courses" — daily injections for 10-20 days, then off for months
• Most users run 1-2 courses per year
• Allergic reactions are the primary side effect concern (it is a porcine-derived biologic)

For dosing, course schedules, sourcing considerations, and integration with other cognitive interventions, see the Cerebrolysin Protocol Guide.

P21 + Cortexin — Russian Neuroprotection

These two compounds occupy a middle ground — more clinical exposure than Dihexa, less than Cerebrolysin, and rooted firmly in the Russian neuropharmacology tradition.

P21

• A peptide derived from a region of ciliary neurotrophic factor (CNTF)
• Proposed mechanism: support of adult neurogenesis, particularly in the hippocampus
• Evidence base: limited preclinical, minimal human data
• Frequently paired with Dihexa in online protocols. No clinical research supports that combination, and the Dihexa caveats above (retracted mechanism paper, unresolved c-Met oncogenic concern) apply in full

Cortexin

• A polypeptide preparation extracted from porcine or bovine cerebral cortex
• Conceptually similar to Cerebrolysin but distinct in composition and Russian regulatory status
• Used clinically in Russia for stroke recovery, encephalopathy, and developmental conditions in children
• Administered as an intramuscular injection, typically in 10-day courses

Evidence Quality Caveat

Russian clinical pharmacology operates under genuine regulatory oversight, but with methodological norms — sample sizes, blinding standards, publication practices — that differ from current Western pharmaceutical research expectations. The available studies are real research, not fabricated, but they should be weighted appropriately when comparing against FDA-approved medications backed by large multi-center trials. For Cortexin specifically, a 2021 systematic review of animal-derived nootropics could locate only one eligible trial (80 participants) — too little to meta-analyse (PMID 36324709). For P21, there is no published human trial at all.

For the full breakdown of both compounds, sourcing reality, and how they fit into a thoughtful cognitive protocol, see the P21 + Cortexin Protocol Guide.

Sample Cognitive Stacks

These stacks are illustrative and represent commonly discussed combinations. They are not prescriptive recommendations. Individual response varies dramatically.

Amounts and timings are omitted for the same reason as above — see the linked protocol guides. Dihexa appears in none of these stacks. A page that flags both a retracted mechanism paper and an oncogenic signalling pathway cannot then put the compound in a suggested stack.

A repeated principle from clinical pharmacology: when evaluating a new compound for your own response, change one variable at a time. Stacking four peptides on day one makes it impossible to know what is helping, hurting, or doing nothing.

Compared to Other Nootropics

The honest framing: peptides are not a cheat code that makes other nootropics obsolete. They are another tool — one that requires more cost, more sourcing diligence, and more careful self-evaluation than a $20 bottle of L-theanine.

Realistic Effects

Hype around cognitive peptides has outpaced the evidence. Here is what realistic expectations look like.

Acute Effects (Single Dose)

• Semax: Onset typically 30-60 minutes after intranasal administration. Subjective effects: a feeling of "lifting" cognitive fog, improved focus, reduced mental fatigue. Duration 4-6 hours.
• Selank: Similar onset window. Subjective effects: reduced background anxiety, smoother thought process, less internal noise. Duration 4-8 hours.
• Dihexa: No reliable acute subjective effect reported by most users — claimed effects develop over weeks.
• Cerebrolysin: No acute "feel" per dose — benefits emerge over a course.

Chronic Effects (Weeks to Months)

Russian clinical protocols dose Semax and Selank in courses rather than one-offs — the post-stroke study above used two 10-day courses (PMID 29798983) — on the premise that the meaningful effects are cumulative: improvements in baseline cognitive function, stress resilience, and emotional regulation that build over weeks of consistent use. Note that this is how the trials were designed, not a finding from head-to-head comparisons of acute versus chronic dosing.

Individual Variability Is Enormous

Some users report dramatic, life-changing effects from Semax. Others feel nothing. This range is not unique to peptides — it mirrors the variability seen with SSRIs, stimulants, and most CNS-active compounds. Genetic differences in melanocortin receptor expression, BDNF signaling, baseline neurotransmitter status, and life stressors all contribute.

The honest framing: if you try Semax for two weeks at a reasonable dose and feel nothing, it is unlikely to become your transformative cognitive tool no matter how long you continue.

Side Effects & Safety

Generally Well-Tolerated

Semax and Selank have a remarkably clean side effect profile in available research and decades of clinical use:

• No documented dependence or withdrawal
• No documented impact on sleep architecture when dosed in the morning
• Rare reports of mild headache or nasal irritation (intranasal forms)
• No known significant drug interactions in published literature

Dihexa Safety Caveats

Already addressed above, but worth repeating: the c-Met oncogenic concern is theoretical but biologically grounded. Conservative practice means short cycles, no chronic use, and complete avoidance in anyone with cancer history.

Cerebrolysin Allergic Potential

As a porcine-derived biologic, Cerebrolysin can provoke allergic reactions in sensitive individuals. Most clinical protocols start with a small test dose. Contraindicated in those with severe allergic disorders or epilepsy in some product labels.

What We Don't Know

• Long-term effects (decades) of any of these compounds in healthy users
• Interactions with common psychiatric medications (SSRIs, stimulants, antipsychotics)
• Effects during pregnancy, breastfeeding, or in pediatric populations (outside specific Russian indications)
• Cumulative effects of polypeptide stacking

Source Authenticity Risk

This is arguably the single most important section in this hub.

Russian-origin peptides, particularly Semax and Selank, have one of the largest counterfeit markets in the entire research chemical space. Demand has outpaced legitimate supply, and unscrupulous vendors sell vials labeled as Semax that contain anything from underdosed product to inert powder to unrelated compounds.

Practical Verification Steps

• Buy only from vendors with a documented history of third-party Certificate of Analysis (COA) testing
• Verify COAs are batch-specific and recent — generic COAs are a red flag
• Use peptide community review databases — Reddit's r/Peptides, vendor scorecards, and Peptides.NYC's own vendor scorecard framework
• Be skeptical of dramatic price differences from market norms
• Reconstitution behavior (clarity, pH, dissolution) provides limited but real signal

The honest reality: even careful sourcing carries some risk in this space. This is one of many reasons to start with a conservative dose, a single compound, and a structured self-evaluation period — not a five-peptide stack from an unknown vendor. The sourcing library collects the COA, vendor and compounding-pharmacy guides in one place.

For Specific Use Cases

Students / Exam Prep

Semax (NA-Semax) is the most discussed compound for sustained study sessions. Reasonable practice: trial it well before any high-stakes exam, never on exam day for the first time. L-theanine + caffeine plus sleep hygiene plus spaced repetition will outperform any peptide for most students.

Founders / Intense Work

The NA-Semax + NA-Selank stack is the most commonly discussed combination in the founder/biohacker community. The pairing aims to handle both the focus demand and the stress load of intense work. Cycle to avoid receptor adaptation.

Recovery from TBI

Cerebrolysin has the strongest clinical evidence here. Anyone considering peptide-based TBI recovery should be working with a knowledgeable physician — not self-experimenting.

Post-COVID Cognitive Issues

"Brain fog" following COVID infection has driven significant interest in cognitive peptides. Anecdotal reports favor Semax and Cerebrolysin. Formal clinical evidence is limited and emerging. This is an area where realistic expectations matter — not all post-viral cognitive symptoms respond to any intervention.

Age-Related Cognitive Decline

This is the indication where Cerebrolysin has the most evidence. The longevity-overlap peptides (Pinealon, Epitalon) are speculative for cognition but commonly discussed in this demographic. Lifestyle interventions — exercise, sleep, social engagement, blood sugar control — outperform any peptide for general age-related decline.

ADHD

Important caveat: Semax has Russian regulatory approval for some attention-related indications in children. This does not make it an ADHD treatment in the FDA sense. Anyone with diagnosed ADHD should work with a qualified clinician on evidence-based management. Peptides may be a complement or experimental adjunct in some cases, but they are not a replacement for proper diagnostic and therapeutic care. This is not medical advice.

Cycling Strategy

No week counts appear here. None of the cycling schedules that circulate for these compounds derives from a published human study comparing one schedule against another, and setting them out in a table implies a precision that does not exist. What can honestly be said is how each compound is used, and why:

• Semax and Selank are run in blocks of a few weeks with a washout before reassessing. The stated rationale is receptor reset, which is argued rather than demonstrated; the defensible reason is that a break is the only way to see your own baseline. Amounts and timing are in the NA-Semax + NA-Selank Protocol Guide and the Semax Amidate Protocol, which carry their own references.
• Cerebrolysin and Cortexin are given as short intensive courses repeated once or twice a year rather than continuously. That pattern reflects how they are prescribed clinically outside the US, not a trial that tested courses against continuous dosing — and note that Cochrane graded the Cerebrolysin evidence very low quality (PMID 31710397). See the Cerebrolysin Protocol Guide and the P21 + Cortexin Protocol Guide.
• P21 is used in short blocks with generous off-time, for the straightforward reason that its safety data is limited.
• Dihexa is absent here for the same reason it is absent from the stacks above: publishing any use schedule for it would be use guidance for a compound whose mechanism paper was retracted and whose target pathway is an established oncogenic driver.

For the general framework, see Peptide Cycling Strategies.

The general principle: peptide cycling is not just about tolerance. It is about creating intentional evaluation windows. If you cannot remember what your baseline feels like, you cannot evaluate whether a compound is actually helping.

Frequently Asked Questions: Cognitive Peptides

Are cognitive peptides legal in the United States? They occupy a research chemical gray area. They are not approved by the FDA for human use, but they are not controlled substances. Sale is typically for "research purposes only." This regulatory status can change.

Will Semax show up on a drug test? Standard drug tests do not screen for Semax or Selank. They are not chemically related to stimulants or controlled substances. This does not constitute legal or compliance advice.

Can I take Semax with my SSRI / stimulant / ADHD medication? There is no rigorous human research on these interactions. Anecdotal use is widespread but unverified. Consult a clinician familiar with both.

How long until I feel something from Semax? Acute effects from a single dose: 30-60 minutes. Cumulative effects: typically evaluable over 2-4 weeks.

Why nasal administration? The Pro-Gly-Pro tail provides stability, and intranasal delivery offers reasonable CNS exposure without injection. Some users do use subcutaneous Semax — practices vary.

Is Dihexa safe? This is the most important caveat in this hub. The c-Met pathway is implicated in oncogenesis, long-term human safety data does not exist, and the 2014 paper that established Dihexa's proposed mechanism was retracted by its journal in April 2025. Many cautious users avoid Dihexa entirely.

What's the difference between Semax and NA-Semax? N-Acetyl Semax and the Amidate variant are chemically modified forms sold as more stable and more potent per microgram. A PubMed search returns no published human or animal study of the N-acetyl amidate variant specifically, so that potency ranking rests on vendor claims and user reports rather than published data. Most current users nonetheless prefer the modified forms.

Can I stack cognitive peptides with creatine, omega-3s, or other supplements? There are no documented dangerous interactions with common supplements. Stacking too much at once defeats your ability to evaluate any single intervention.

How do I know if my Semax is real? You cannot definitively confirm authenticity without testing. Use vendors with batch-specific third-party COAs, a track record in the community, and reasonable pricing.

Should I try peptides before more basic interventions? Almost never. Sleep, exercise, nutrition, light exposure, stress management, and basic supplements (creatine, omega-3, magnesium) will outperform any peptide stack for the vast majority of people. Peptides are a layer on top of fundamentals — not a substitute for them.

Featured Protocols on Peptides.NYC

Explore the full protocols for each compound discussed in this hub:

• NA-Semax + NA-Selank Protocol Guide — The classic calm-focus stack, dosing breakdown, intranasal protocols, cycling
• Semax Amidate Protocol — The further-modified Semax variant for users seeking maximum potency
• Dihexa Protocol Guide — Mechanism, dosing, and a thorough discussion of the c-Met safety concern
• Cerebrolysin Protocol Guide — The clinically-substantiated brain extract, course-based protocols, sourcing
• P21 + Cortexin Protocol Guide — Russian neuroprotection peptides, evidence quality, integration
• Cognitive Peptide Stack Guide — Full stacking protocols, sequencing, evaluation framework
• Semax vs Selank — Head-to-head comparison of the two Russian nootropic peptides
• Nootropic Peptides for Brain Fog and Focus — What the research shows for post-viral and everyday brain fog
• Peptides for Anxiety — Selank and the anxiolytic evidence, without the hype

Related Hubs on Peptides.NYC

• Healing & Recovery Peptide Hub — BPC-157, TB-500, and tissue repair peptides
• Longevity Peptide Hub — Bioregulators, Epitalon, MOTS-c, and aging
• Muscle & Performance Peptide Hub — Growth hormone secretagogues and body-composition peptides
• Sleep Peptide Hub — DSIP, Pinealon, and pre-bed GH secretagogues

Final Word

Cognitive peptides represent a genuinely interesting frontier in personal optimization. They are not a replacement for fundamentals — sleep, movement, nutrition, and stress management remain the highest-leverage levers for cognitive function. They are not a substitute for proper medical care for diagnosed conditions like ADHD, depression, or post-injury cognitive impairment. And they are not without risk — particularly Dihexa's c-Met concern and the pervasive sourcing problem in the Russian peptide market.

But used thoughtfully, with realistic expectations, careful sourcing, structured self-evaluation, and appropriate cycling, peptides like Semax and Selank can be a meaningful layer in a serious cognitive optimization protocol.

Your biology is programmable. The smartest way to program it is slowly, deliberately, and with the humility to recognize what you don't yet know.

Reminder: This content is for educational purposes only and is not medical advice. Always consult a licensed healthcare provider before starting any peptide protocol. Peptides discussed are not FDA-approved for human use in the United States and are sold as research chemicals.

Selected References

Every PMID linked above points to the PubMed record for that paper, so you can check the claim against the abstract yourself. These are the primary sources this hub relies on.

1. Dolotov OV, Karpenko EA, Inozemtseva LS, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research. 2006. PMID 16996037
2. Dolotov OV, Karpenko EA, Seredenina TS, et al. Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain. Journal of Neurochemistry. 2006. PMID 16635254
3. Gusev EI, Martynov MY, Kostenko EV, et al. The efficacy of semax in the treatment of patients at different stages of ischemic stroke. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2018. PMID 29798983
4. Zozulia AA, Neznamov GG, Siuniakov TS, et al. Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2008. PMID 18454096
5. Kolik LG, Nadorova AV, Antipova TA, et al. Selank, peptide analogue of tuftsin, protects against ethanol-induced memory impairment by regulating of BDNF content in the hippocampus and prefrontal cortex in rats. Bulletin of Experimental Biology and Medicine. 2019. PMID 31625062
6. Benoist CC, Kawas LH, Zhu M, et al. The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-Met system. Journal of Pharmacology and Experimental Therapeutics. 2014. Retracted in 2025 — see reference 7. PMID 25187433
7. Retraction notice to "The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-Met system". Journal of Pharmacology and Experimental Therapeutics. 2025. PMID 40312093
8. Guo R, Luo J, Chang J, et al. MET-dependent solid tumours — molecular diagnosis and targeted therapy. Nature Reviews Clinical Oncology. 2020. PMID 32514147
9. Cui S, Chen N, Yang M, et al. Cerebrolysin for vascular dementia. Cochrane Database of Systematic Reviews. 2019. PMID 31710397
10. Alsulaimani RA, Quinn TJ. The efficacy and safety of animal-derived nootropics in cognitive disorders: systematic review and meta-analysis. Cerebral Circulation — Cognition and Behavior. 2021. Subject of a 2022 erratum — see reference 11. PMID 36324709
11. Erratum regarding previously published articles. Cerebral Circulation — Cognition and Behavior. 2022. PMID 36326279

This list is not exhaustive, and inclusion here is not endorsement — reference 6 is listed precisely because it was retracted, and reference 10 because it carries an erratum. Nothing on this page is medical advice.