This paper found a correlation between the time that female subjects went to sleep and how much sebum their skin produced.
A slight increase in sebum production was seen the later they went to sleep. As well, sleeping less was correlated with a slight decrease in sebum production. This relationship wasn’t seen in the male participants of the study.
They also found a correlation between levels of free testosterone and 5α-reductase (an enzyme that converts testosterone in to dihydrotestosterone – a more active form).
Curiously this correlation was, again, only significant for women – despite men having 10 times more free testosterone than women. The researchers think that there may be a maximum threshold for how much testosterone can influence sebum production. There’s also research indicating that the sebaceous gland’s sensitivity to testosterone varies among individuals as well.
While the study’s sample size was quite small, and it’s completely possible this isn’t reproducible, due to random chance or some other variable…there is newer research describing a pathway between inflammation and sebum production – which may be what’s at play here.