{"id":"2dd92967-9f30-5916-9236-417b5f2ed96b","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-tolerance","predicate":"shows_endpoint_specific_tolerance","statement":"Tolerance occurred on subjective measures but not the measured physiological endpoints; chronic effects remained mainly on EEG beta-2 power.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"5270b9b6-a9cf-564e-adac-c8a2edf6954d","mechanism_event_label":"Feeling tolerant did not mean every measured response had disappeared.","subject":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"object":{"id":"3fc34680-841b-58eb-a72f-dfc989d33b67","slug":"subjective-fatigue","display_name":"Subjective fatigue","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"5270b9b6-a9cf-564e-adac-c8a2edf6954d","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-tolerance-event","event_type":"observed_relationship","label":"Feeling tolerant did not mean every measured response had disappeared.","description":"Tolerance occurred on subjective measures but not the measured physiological endpoints; chronic effects remained mainly on EEG beta-2 power.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"3fc34680-841b-58eb-a72f-dfc989d33b67","slug":"subjective-fatigue","display_name":"Subjective fatigue","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"16 regular users; double-blind within-subject study; at least 14 days on 400 mg/day or placebo, with acute challenges.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"No universal claim that caffeine never benefits performance; these results concern the selected outcomes and schedule.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Caffeine collection; salts, coffee, species and coexposure contexts retain their identities.","comparator":null,"unit":null,"notes":"","entity":{"slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Feeling tolerant did not mean every measured response had disappeared.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Caffeine withdrawal, acute effects, tolerance, and absence of net beneficial effects of chronic administration: cerebral blood flow velocity, quantitative EEG, and subjective effects. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19241060/ · DOI 10.1007/s00213-009-1489-4","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"dc7b4ba2-4427-5584-b4c2-1ea80a97a608","evidence_kind":"source_excerpt","locator":"Lines 140-146","start_line":140,"end_line":146,"excerpt":"## caf-tolerance\nFeeling tolerant did not mean every measured response had disappeared.\nTolerance occurred on subjective measures but not the measured physiological endpoints; chronic effects remained mainly on EEG beta-2 power.\nModel: 16 regular users; double-blind within-subject study; at least 14 days on 400 mg/day or placebo, with acute challenges.\nLimitations: No universal claim that caffeine never benefits performance; these results concern the selected outcomes and schedule.\nEvidence access: Primary abstract\nCaffeine withdrawal, acute effects, tolerance, and absence of net beneficial effects of chronic administration: cerebral blood flow velocity, quantitative EEG, and subjective effects. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19241060/ · DOI 10.1007/s00213-009-1489-4","model_system":"16 regular users; double-blind within-subject study; at least 14 days on 400 mg/day or placebo, with acute challenges.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access stated with the claim.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"40a654db-878c-5471-bc6c-88f4f52599c0","stable_key":"import-ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6","title":"Caffeine: receptors, metabolism, nutrient interactions, adaptation and discovery questions (2026-09-18)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. 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