Globally, there is evidence that the average age of pubertal onset among girls has decreased considerably compared to the twentieth century, with implications for their welfare and their future. In addition, adolescents and young adults have higher rates of allergies, higher awareness and diagnoses of mental health problems, and are more likely to be sleep-deprived, In many countries, youths are more likely to have intellectual disabilities and psychiatric disorders than older people. In some European nations, they are facing declining cognitive abilities, especially among the cognitive elites.