Final answer:
About 15-20% of adolescents experience major depressive disorder during their lifetime, a condition that greatly affects personal and public healthcare due to its complexity and impact on daily life.
Step-by-step explanation:
In the context of adolescents, the estimated lifetime prevalence of major depressive disorder (MDD) is approximately 15-20%, according to various studies. For example, a study by Kessler in 1994 found a lifetime prevalence estimate of 15-20% for MDD. Similarly, a study by Bromet et al. in 2011 reported a range of 4-7% for the point prevalence of MDD. MDD is a significant mental health issue among adolescents, and it is important to seek professional help and support if experiencing symptoms of depression.