This study is highly specific, leaving room for other investigators to do other specific investigations:
“Effects of Makeup, Perfume and Skincare Product Usage and Hair Care Regimen on Circadian Typology, Sleep Habits and Mental Health in Female Japanese students Aged 18-30,” Risa Nishihara, Kai Wada, Osami Akimitsu, Milada Krejci, Teruki Noji, Miyo Nakade, Hitomi Takeuchi, Tetsuo Harada, Psychology, vol. 4, no. 3, March 2013. The authors, at Kochi University, Japan, the University of South Bohemia, Czech Republic, and Tokai Gakuen University, Japan, explain:
“The students who regularly carried out a hair care regimen showed a significantly lower frequency of becoming angry after a small trigger and of losing control due to anger than those who did not. Makeup, perfume and skin care products might be possible to be related to better sleep health for students. Moreover, hair care may help maintain mental health in female students. Makeup, perfume and skin care products might be implied to become chemical, mechanical and/or psychological stimuli as zeitgebers for circadian clock of students.”
(Thanks to investigator Neil Martin for bringing this to our attention.)
BONUS (probably unrelated): The corpse treatment patents assigned to Risa Nishihara (who may well be a different Risa Nishihara from the lead author of the hair care study)