stimulates / stimulatedBy

Properties expressing biological activation relationships where one entity enhances, upregulates, or triggers increased activity in another. stimulatedBy is the inverse property.

Canonical URLs: https://healthschema.org/stimulates, https://healthschema.org/stimulatedBy

Namespace: hs:

Category: Biological Relationship Property

Inverse: stimulates ↔ stimulatedBy

Why These Properties Exist

Biological systems are fundamentally about regulation—growth factors stimulate cell division, hormones trigger metabolic changes, drugs activate receptors. Yet schema.org provides no direct way to express these activation relationships.

When marking up health content, we frequently need to state things like:

"PDGF stimulates fibroblast proliferation"
"Vitamin D stimulates calcium absorption"
"Collagen synthesis is stimulated by TGF-β"

Without explicit relationship properties, this information either gets buried in text descriptions or lost entirely. The stimulates and stimulatedBy properties enable:

Knowledge graph traversal: Query "what stimulates collagen production?" and get structured answers
Mechanistic clarity: Make causal relationships explicit rather than implicit
Treatment understanding: Show how interventions work by linking them to what they activate
Biological pathway modelling: Connect entities in regulatory networks

Alignment with Established Ontologies

This property aligns with the Gene Ontology's positively_regulates relationship and similar concepts in biological ontologies. The terminology "stimulates" was chosen for accessibility to general audiences whilst maintaining semantic precision.

Domain and Range

stimulates — Used On (Domain)

Type	Context
schema:ChemicalSubstance	Vitamins, hormones, signalling molecules that activate processes
schema:Protein	Growth factors, cytokines, enzymes that trigger biological responses
hs:BiologicalProcess	Processes that trigger other processes (e.g., inflammation stimulates healing)
schema:Drug	Pharmaceutical agents that activate biological targets
schema:AnatomicalStructure	Cells or structures that activate others (e.g., neurons stimulating muscle)

stimulates — Expected Values (Range)

Type	Context
hs:BiologicalProcess	Cellular activities, metabolic processes, physiological responses being activated
schema:ChemicalSubstance	Substances whose production or activity is increased
schema:Protein	Proteins whose expression or activity is upregulated
schema:AnatomicalStructure	Cells or tissues being activated (e.g., immune cells, glands)

stimulatedBy — Domain and Range

The inverse property stimulatedBy has the domain and range reversed—it's used on the entity being activated, pointing to what activates it.

Relationship Semantics

Inverse Relationship

stimulates and stimulatedBy are formal inverses. If A stimulates B, then B is stimulatedBy A:

Statement	Equivalent Inverse
EGF stimulates keratinocyte proliferation	Keratinocyte proliferation stimulatedBy EGF
VEGF stimulates angiogenesis	Angiogenesis stimulatedBy VEGF

Both directions are valid; choose based on what you're describing. When documenting a growth factor, use stimulates. When documenting a process, use stimulatedBy to list its activators.

Not Transitive

If A stimulates B, and B stimulates C, it does NOT follow that A stimulates C. Each relationship must be explicitly stated.

Strength and Directness

This property indicates positive regulatory effect but doesn't capture:

Magnitude: How strong the stimulation is
Directness: Whether the effect is direct or mediated
Conditions: Under what circumstances the stimulation occurs

Use description to qualify these aspects when important. Future versions may add qualified relationship patterns.

Distinction from Related Concepts

Relationship	Meaning	Example
stimulates	Increases activity, expression, or rate	PDGF stimulates fibroblast migration
produces	Synthesises or generates (biosynthesis)	Fibroblasts produce collagen
inhibits	Decreases activity (opposite of stimulates)	Cortisol inhibits collagen synthesis

Usage Guidance

Do

Use for regulatory relationships—where one entity increases the activity or expression of another
Reference defined entities—use @id to link to entities defined elsewhere in your schema
Consider bidirectional declaration—declare from both sides for complete graph traversal
Combine with evidenceSource—link stimulation claims to supporting research
Use arrays for multiple targets—a growth factor may stimulate several processes

Don't

Confuse with produces—stimulation increases activity; production creates new substance
Use for physical causation—"heat stimulates sweating" is better modelled as a CausalPathway
Assume directionality—always specify which entity stimulates which
Overstate certainty—if the relationship is hypothesised, note this in description

Choosing Between stimulates and stimulatedBy

You're documenting...	Use this property	Example
An activator (growth factor, drug)	`stimulates`	EGF entity → lists what it stimulates
A process or target	`stimulatedBy`	Collagen synthesis entity → lists what stimulates it
Both perspectives	Both properties	Full bidirectional declaration for graph completeness

Examples

Example 1: Growth Factor Stimulating a Process

Documenting that PDGF activates fibroblast proliferation:

{
  "@type": "Protein",
  "@id": "#Protein/PDGF",
  "name": "Platelet-derived growth factor",
  "alternateName": "PDGF",
  "stimulates": [
    {"@id": "#BiologicalProcess/FibroblastProliferation"},
    {"@id": "#BiologicalProcess/FibroblastMigration"}
  ],
  "description": "Major growth factor released from platelet alpha granules during activation"
}

Why this works: The growth factor is the subject; what it activates are the objects. Multiple targets are expressed as an array.

Example 2: Process Listing Its Activators

From the perspective of the process being activated:

{
  "@type": "BiologicalProcess",
  "@id": "#BiologicalProcess/CollagenSynthesis",
  "name": "Collagen synthesis",
  "description": "The biosynthesis of collagen molecules by fibroblasts",
  "stimulatedBy": [
    {"@id": "#Protein/TGF-beta"},
    {"@id": "#Protein/PDGF"},
    {"@id": "#Protein/IGF-1"}
  ]
}

Why this works: Lists all known activators of a process in one place—useful for understanding what promotes a desired outcome.

Example 3: Bidirectional Declaration

Complete graph with both directions specified:

{
  "@graph": [
    {
      "@type": "Protein",
      "@id": "#Protein/VEGF",
      "name": "Vascular endothelial growth factor",
      "alternateName": "VEGF",
      "stimulates": {"@id": "#BiologicalProcess/Angiogenesis"}
    },
    {
      "@type": "BiologicalProcess",
      "@id": "#BiologicalProcess/Angiogenesis",
      "name": "Angiogenesis",
      "description": "Formation of new blood vessels from existing vasculature",
      "stimulatedBy": {"@id": "#Protein/VEGF"}
    }
  ]
}

Why bidirectional: Enables queries from either direction—"What does VEGF stimulate?" or "What stimulates angiogenesis?"

Example 4: Drug Stimulating a Target

Pharmaceutical activation relationship:

{
  "@type": "Drug",
  "@id": "#Drug/Minoxidil",
  "name": "Minoxidil",
  "alternateName": "Regaine",
  "stimulates": [
    {"@id": "#BiologicalProcess/HairFollicleProliferation"},
    {"@id": "#BiologicalProcess/Vasodilation"}
  ],
  "description": "Topical treatment that prolongs anagen phase and increases blood flow to follicles"
}

Example 5: With Evidence Source

Combining stimulation relationship with supporting evidence:

{
  "@type": "Protein",
  "@id": "#Protein/EGF",
  "name": "Epidermal growth factor",
  "stimulates": {
    "@type": "BiologicalProcess",
    "@id": "#BiologicalProcess/KeratinocyteProliferation",
    "name": "Keratinocyte proliferation",
    "description": "Increased division rate of epidermal keratinocytes"
  },
  "evidenceSource": {
    "@type": "ScholarlyArticle",
    "@id": "https://doi.org/10.1016/j.cell.2019.example",
    "name": "EGF receptor signalling in epidermal homeostasis"
  }
}

Why this works: Links the mechanistic claim to supporting research, enabling verification.

Example 6: Within a CausalStep

Enhancing a causal pathway step with explicit entity relationships:

{
  "@type": "CausalStep",
  "stepNumber": 2,
  "mechanism": "Growth factors bind to receptor tyrosine kinases on fibroblast surfaces",
  "result": "Intracellular signalling cascades activate proliferation genes",
  "stimulates": {"@id": "#BiologicalProcess/FibroblastProliferation"},
  "evidenceSource": {"@id": "#Reference/Marx2004"}
}

Why this works: The mechanism and result describe what happens; stimulates creates an explicit link to the activated process for graph traversal.

Implementation Notes

Graph Queries

Example SPARQL queries enabled by this property:

Find all stimulators of collagen synthesis:

SELECT ?stimulator ?name WHERE {
  ?stimulator hs:stimulates <#BiologicalProcess/CollagenSynthesis> .
  ?stimulator schema:name ?name .
}

Find what a growth factor activates:

SELECT ?target ?name WHERE {
  <#Protein/TGF-beta> hs:stimulates ?target .
  ?target schema:name ?name .
}

Build an activation network:

SELECT ?source ?target WHERE {
  ?source hs:stimulates ?target .
  ?source a schema:Protein .
}

JSON-LD Processing

In the Health Schema context, both properties are defined with @type: @id, meaning values should be references to other entities rather than literal strings.

Validation

Standard schema.org validators will not recognise these properties. This is expected for Health Schema extensions. The properties are defined in the Health Schema context and will be correctly interpreted by systems that load this context.

Future Considerations

Potential enhancements under consideration:

Qualified relationships with strength indicators
Conditional stimulation (only under certain circumstances)
Direct vs. indirect stimulation distinction