A single universal age cut-off is not appropriate because products differ by formulation and regulatory category, and evidence varies by age group.\n\nAs a safety principle, use in individuals under 18 should be clinician-guided. For pediatric focus/learning concerns, first assess sleep, screen exposure, nutrition, and common deficiencies.\n\nIn adults, age alone is not the key factor—comorbidities, medications, and tolerance matter. In older adults, interaction assessment becomes more important due to polypharmacy.\n\nBottom line: under 18—medical guidance; adults—individual risk–benefit assessment.