Experts disagree about the data that show an earlier onset of depression and bipolar disorder in every successive generation since the first World War (this change is called the cohort effect). Nonetheless, it is interesting that so many other medical conditions are increasingly seen in young children. These include asthma, arthritis, obesity, allergy, diabetes, and a host of other conditions. WebMD reported that menarche and the onset of puberty are also occurring at younger ages. Puberty used to be a largely teenage occurrence, and now it occurs in many children as early as age 7.