Energy, Cognition & Mood
Peptides for Depression & Mood: Evidence Review (2026)
A clinical, evidence-graded look at the three peptides marketed for depression — Cerebrolysin, Selank and Semax — separating secondary-endpoint human data and preclinical antidepressant signals from marketing hype.
CerebrolysinSelankSemaxBDNFevidence-graded
The quick verdict
An honest, evidence-graded ranking of the three peptides marketed for depression — and why none is a proven human antidepressant.
- Best overall
- Cerebrolysin — The only peptide with any human depression-relevant outcome — a secondary Geriatric Depression Scale benefit in a stroke RCT (Grade B), though mixed and never tested in primary MDD.
- Best value
- Cerebrolysin — Also the best-evidenced choice; the intranasal alternatives (Selank, Semax) have no human depression data to justify them, so nothing cheaper is better supported.
- Best for Depression-relevant mood signal backed by any human data at all
- Cerebrolysin — Its secondary post-stroke GDS benefit is the sole human mood outcome in the group — Selank and Semax are animal-only for depression.
How we evaluated
We ranked each peptide strictly by the strength of human evidence for depression as a measured endpoint — not fame, mechanism elegance, or evidence for other conditions. Human trials outrank animal data, which outrank in-vitro and mechanism-only reasoning; hypothesis papers, anecdote and vendor copy do not count as efficacy. Evidence grades follow PeptideVox's A-to-D ramp (A = human RCT/meta; B = lower-tier human/secondary-endpoint; C = preclinical only; D = anecdotal/hypothesis/marketing).
- Human depression evidence. Whether any published human study used a depression endpoint (primary or secondary) in an actual patient population.
- Evidence quality. Trial size, controls, whether depression was primary vs secondary, and whether effect sizes and p-values were reported.
- Mechanistic coherence. Whether a plausible mechanism (BDNF/TrkB restoration, monoamine modulation) supports the claim — noting that mechanism is not proof.
- Safety & fit. Tolerability and interaction risk for a depression indication specifically, including combination with prescribed antidepressants.
- Regulatory honesty. FDA approval/compounding status and WADA exposure, stated plainly rather than glossed over.
Rating scale: 1-5 stars reflecting human-evidence strength for depression: 5 = robust human RCT data; 1 = mechanism/hypothesis only. Star ratings track the per-item evidence grade.
Last verified .
At a glance
| # | Name | Evidence | Rating | Best for | Pricing |
|---|---|---|---|---|---|
| 1 | Cerebrolysin | B | 2.5 | Understanding the ceiling of human peptide evidence for depression — a secondary, mixed signal, not a treatment | Not FDA-approved/marketed in US; not a sourcing recommendation |
| 2 | Selank | C | 2.0 | Illustrating a real preclinical antidepressant signal that has never been tested in depressed humans | Research chemical / not FDA-approved; not a sourcing recommendation |
| 3 | Semax | C | 1.5 | Showing how an elegant mechanism and a hypothesis paper get mistaken for antidepressant proof | Research chemical / not FDA-approved; not a sourcing recommendation |
Cerebrolysin
The only peptide with any human depression-relevant data
Cerebrolysin is a parenteral (IV/IM) porcine-brain-derived peptide mixture marketed as a neurotrophic agent, and it is the only compound in this group with any human mood data — but always as a secondary outcome in neurological-recovery populations, never in primary major depressive disorder. In the randomized, placebo-controlled, double-blind CARS stroke trial (30 mL/day IV for about 21 days, n≈205), the Geriatric Depression Scale was among the secondary measures showing a "medium" benefit favoring Cerebrolysin at day 90, though no standalone GDS p-value was reported. In moderate-to-severe traumatic brain injury, a retrospective CAPTAIN-II analysis (n=125) found a large effect on anxiety but no statistically significant between-group difference on depression — so even the human signal is mixed: anxiety yes, depression not clearly. A 2025 scoping review judged its overall psychiatric evidence base limited. Its animal antidepressant data are more consistent than the human depression data — reversal of reserpine-induced depression, potentiation of lithium, and improvement of post-ischemic depression models. It grades B, but with the important caveat that this "B" rests entirely on secondary endpoints, not a dedicated Western depression trial. It is not FDA-approved or marketed in the US.
Strengths
- Only peptide here with any human depression-relevant outcome (secondary GDS benefit after stroke)
- Most consistent animal antidepressant data of the three (reserpine, lithium-potentiation, post-ischemic models)
- Coherent neurotrophic mechanism raising BDNF and reducing oxidative stress in models
Weaknesses
- Only Grade B, and only via secondary endpoints — no dedicated primary-MDD RCT exists
- Human signal is mixed: positive on stroke GDS but null on the TBI depression subscale
- Parenteral only, additive effects with antidepressants, BP elevation with high-dose MAOIs; not FDA-approved in the US
- Best for
- Understanding the ceiling of human peptide evidence for depression — a secondary, mixed signal, not a treatment
- Pricing
- Not FDA-approved/marketed in US; not a sourcing recommendation
Selank
Real animal antidepressant data, no human depression trial
Selank is a synthetic heptapeptide analog of the immunopeptide tuftsin, developed in Russia as a non-sedating anxiolytic. For depression specifically, it has genuine, dedicated animal data but no human trial. In the genetically depression-prone WAG/Rij rat model and a stress-provoked BALB/c mouse model, Selank reduced forced-swim immobility and reversed anhedonia (a sucrose-preference deficit), demonstrating a real "antidepressant component" in its activity spectrum; it also potentiated diazepam's effect under chronic mild stress and modulates brain monoamines and serotonin. The catch is that its only human trial was in generalized anxiety disorder and neurasthenia, not depression — a 62-patient comparison against the benzodiazepine medazepam, where it matched benzodiazepine anxiolysis with an added antiasthenic, anti-fatigue effect and no sedation. That anti-fatigue component overlaps clinically with depressive-spectrum symptoms, which is why Selank is sometimes discussed for mood, but anxiety efficacy is not depression efficacy, and the trial used no depression-primary design. A human resting-state fMRI study found Selank altered amygdala-temporal connectivity, a plausible neural correlate of an affective effect but not a symptom outcome. For depression it grades C: a genuine animal signal, an empty human cupboard.
Strengths
- Dedicated animal antidepressant data (reversed forced-swim immobility and anhedonia in depression models)
- Non-sedating human anxiolytic track record with an anti-fatigue component that overlaps depressive symptoms
- Coherent mechanism via BDNF, monoamine modulation and enkephalin stabilization
Weaknesses
- No human depression trial at all — human data are for anxiety/neurasthenia, not depression
- Antidepressant evidence is animal-only, hence Grade C for depression
- Near-absent long-term and psychiatric-population safety data; not FDA-approved
- Best for
- Illustrating a real preclinical antidepressant signal that has never been tested in depressed humans
- Pricing
- Research chemical / not FDA-approved; not a sourcing recommendation
Source: Sarkisova et al., Zh Vyssh Nerv Deiat 2008 (PMID 18661785)
Semax
Antidepressant-shaped mechanism, hypothesis-only evidence
Semax is a synthetic heptapeptide analog of ACTH(4-10), used intranasally, whose best-evidenced indication in Russia is acute ischemic stroke, not mood. Mechanistically it is the most "antidepressant-shaped" of the three — rapid hippocampal BDNF and TrkB upregulation plus dopaminergic and serotonergic modulation — but its depression evidence is the weakest in the group. No human depression trial exists. The widely cited "Therapeutic Possibility of Semax for Depression" is a 2008 two-page hypothesis commentary that presents no original data, reasoning purely from Semax's BDNF/TrkB and dopaminergic effects. The only depression-relevant experimental data are animal and appear only under elevated stress: in rats, intranasal Semax had no effect on normal emotional state but normalized CCK-4-induced anxiety and depression in the forced-swim test. Its human data exist but are for stroke recovery and cognition, including raised plasma BDNF after stroke — not depression. An important fit caveat is that Semax is mildly stimulating and dopaminergic, which is not obviously matched to every depressive presentation and warrants theoretical caution with stimulants. It is on the FDA's July 2026 compounding review agenda, but for compounding eligibility and non-depression indications. For depression it grades C-to-D.
Strengths
- Most coherent antidepressant-type mechanism of the three (hippocampal BDNF/TrkB plus monoamine activation)
- Genuine human data for stroke recovery, including a measured rise in plasma BDNF
- Animal forced-swim normalization under stress supports the biological plausibility
Weaknesses
- No human depression trial; the main 'Semax for depression' reference is a hypothesis paper with no data
- Depression-relevant animal effects appear only under elevated stress, not in the normal state
- Mildly stimulating and dopaminergic — an uncertain fit for depression and cautioned with stimulants
- Best for
- Showing how an elegant mechanism and a hypothesis paper get mistaken for antidepressant proof
- Pricing
- Research chemical / not FDA-approved; not a sourcing recommendation
Source: Pae, Therapeutic Possibility of Semax for Depression, CNS Spectrums 2008 (hypothesis)
Feature comparison
| Feature | Cerebrolysin | Selank | Semax |
|---|---|---|---|
| Human depression data | Secondary endpoint only | — | — |
| Evidence grade (depression) | B | C | C-D |
| Dedicated MDD RCT | — | — | — |
| Feature | Cerebrolysin | Selank | Semax |
|---|---|---|---|
| Route | IV/IM (parenteral) | Intranasal | Intranasal |
| Feature | Cerebrolysin | Selank | Semax |
|---|---|---|---|
| FDA compounding review 2026 | — | No (nomination withdrawn) | Yes (July 24, 2026; non-depression) |
| WADA exposure (S0) | Prohibited (catch-all) | Prohibited (catch-all) | Prohibited (catch-all) |
Frequently asked
Is there a peptide proven to treat depression in humans?
No. As of 2026, no peptide on this page has an adequately powered, dedicated human randomized controlled trial showing it treats depression. The closest human data are secondary depression endpoints in Cerebrolysin stroke and traumatic-brain-injury trials, and even those are mixed: positive on the Geriatric Depression Scale after stroke, but null on the depression subscale after TBI. Selank and Semax have no human depression trial at all; their antidepressant signals come only from animal stress models. A widely cited Semax-for-depression reference is a 2008 hypothesis commentary, not a study. None of the three is FDA-approved, and all are sold only as research chemicals. Treat every human antidepressant claim as unproven.
Semax and Selank raise BDNF and serotonin — doesn't that make them antidepressants?
Mechanistic overlap with antidepressants is real but is not proof. Modern models hold that effective antidepressants ultimately restore BDNF/TrkB signaling and synaptic plasticity, and both Semax and Selank do raise BDNF and modulate monoamines in rodents. But a compound can move a biomarker in a rat brain and still do nothing measurable for a depressed person. The antidepressant-like effects of both peptides are demonstrated only in animal stress models — reduced forced-swim immobility, reversed anhedonia — which are hypothesis-generating, not efficacy evidence in humans. The mechanism makes the hypothesis worth testing; it does not make the peptide an antidepressant. No human depression trial has confirmed any of it.
Can I add one of these peptides to my antidepressant?
This is not advisable without a clinician, and this article does not recommend it. Human interaction data with SSRIs, SNRIs and MAOIs are essentially absent for Semax and Selank, so any combination is genuinely uncharacterized. Cerebrolysin's labeling explicitly flags additive effects with antidepressants, and high-dose Cerebrolysin combined with high-dose MAO inhibitors has been reported to raise blood pressure. Stacking serotonergic and monoaminergic agents together carries a theoretical risk of serotonin-related effects. Most importantly, never stop or replace a prescribed antidepressant to try a peptide. If you are considering any change to depression treatment, that decision belongs with a licensed physician who knows your full medication list.
Selank helped anxiety in a trial — does that count for depression?
Not directly. Selank's one human trial was in generalized anxiety disorder and neurasthenia, not depression, and used an anxiety-primary design against the benzodiazepine medazepam. It did show an antiasthenic, anti-fatigue component that overlaps clinically with depressive-spectrum symptoms, which is why Selank is sometimes discussed for mood. But anxiety and depression are distinct conditions, and anxiety efficacy is not depression efficacy. The only dedicated Selank depression data are preclinical — antidepressant-like effects in genetically depression-prone WAG/Rij rats and stressed mice. For depression specifically, the human cupboard is empty, so Selank grades C: a genuine animal signal, no human depression proof.
What should I do instead if I am depressed?
See a licensed clinician for evidence-based care. That means psychotherapy such as CBT or interpersonal therapy, FDA-approved antidepressants where indicated, and, for severe or treatment-resistant cases, options like ketamine or esketamine, transcranial magnetic stimulation, or ECT — all delivered by a professional. From a functional, root-cause angle, also address the high-evidence, low-risk foundations: sleep, nutrition, regular exercise (a genuine BDNF-raiser), thyroid and metabolic workup, nutrient status such as vitamin D, B12, folate, omega-3 and iron, inflammation, and psychosocial drivers. Experimental peptides are not a shortcut around that foundation. If you are in crisis or thinking about suicide, in the US call or text 988 right now.