In Europe and the United States, the average age of the onset of puberty among girls was around 13 in the early twenty-first century, down from about 16 a hundred years earlier. Early puberty is associated with a variety of mental health issues—such as anxiety and depression, as people at this age tend to strongly desire conformity with their peers—, early sexual activity, substance abuse, tobacco smoking, eating disorders, and disruptive behavioral disorders. Girls who mature early also face higher risks of sexual harassment. Moreover, in some cultures, pubertal onset remains a marker of readiness for marriage, for, in their point of view, a girl who shows signs of puberty might engage in sexual intercourse or risks being assaulted, and marrying her off is how she might be 'protected'. To compound matters, factors known for prompting mental health problems are themselves linked to early pubertal onset; these are early childhood stress, absent fathers, domestic conflict, and low socioeconomic status. Possible causes of early puberty could be positive, namely improved nutrition, or negative, such as obesity and stress. Other triggers include genetic factors, high body-mass index (BMI), exposure to endocrine-disrupting substances that remain in use, such as Bisphenol A (found in some plastics) and dichlorobenzene (used in mothballs and air deodorants), and to banned but persistent chemicals, such as dichlorodiphenyl-trichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE), and perhaps a combination thereof (the 'cocktail effect').