How to compare trends of different curves?

Hello everyone,
i'm a newbie here...i'll try to explain, as well as i can, my stat problem: I have to compare trends of sleep during time of three different (beetween factor) groups of subjects (see childlike picture). How can i easily do that? in particular, i would like to highlight that the global progression is different between groups. Thank you for your precious help.

P.S.= I0m using SPSS or Sigmaplot.


This looks like a repeated measures ANOVA problem. Do you have repeated measurements identified by individual observation?