WHO Definition of Teenage Years
The World Health Organization (WHO) defines adolescents as individuals between the ages of 10 and 19 years. 1, 2
Official WHO Age Range
WHO specifically designates the adolescent period as spanning from 10 to 19 years of age, which represents the standard international definition used across global health initiatives and research 1, 2
This 10-19 year age range is distinct from WHO's definition of "youth," which encompasses individuals aged 15-24 years 1
The adolescent population represents approximately 20% of the world's population, with 85% living in developing countries 2
Context and Rationale
The WHO definition is based on the period encompassing physical and sexual maturation, social and economic development, identity formation, and acquisition of adult relationship skills 3
This age range captures the onset of puberty (which has been occurring earlier in recent decades) through the completion of major physical growth milestones 4
The definition recognizes adolescence as a critical "gateway to health" period, since approximately 70% of premature deaths among adults are due to behaviors initiated during adolescence 2
Important Caveats
While WHO uses 10-19 years as the standard definition, some clinical and research contexts extend adolescence to age 21 or even 24 years to account for continued brain development and delayed social role transitions 1, 4
The term "teenager" colloquially refers to ages 13-19 (the "-teen" years), which is narrower than WHO's official adolescent definition that begins at age 10 1
Physical and developmental maturation varies significantly between individuals of the same chronological age, and children with chronic diseases may develop autonomy later than their peers 1