I concur.  I have also found this to be true with teenagers, and perhaps, for the same reasons you so well stated in your post.  I lost a brother to suicide many many moons ago, and it was in May.  I see some behavioral changes in some youngsters I know this season, and they each have a different mental health issue.  People with SAD, can also suffer not only the change from Summer to Fall, but Winter to Spring is now a major problem for some.  I have issues during the change of both seasons.  This certainly is more prevalant with those of us who live in the Northern half of the continent.  I also take note: Children or teens with ADHD are showing more irritability and impulse issues as this season dawns.  I believe, we need to be much more vigilant with helping people during this time.  I think it is important to get out during the times the weather is pleasant, even if it is a little at a time for some people.  Dysensitizing oneself to the environmental changes, like one may need to do with phobia's, and with people who are supportive, can help alleviate some of the feelings of isolation and hybernation that comes far too often with people depressed in the Winter months. 

i feel great depression these days and i think  reason is that i love winter because winter fits my sad mood.i alwasys smile and look happy but i got tons of sadness in my heart and i swear the dark sadness by end of holidays made me hate the holiays itself.i love to be involved in work everyday and spring this year kills me.i need help ,i want cry but i cant,i need help.i hate summer because its hot and i feel people r more happy .if anyone can help me please dont hesitate my mail: ahuk_2010@yahoo.com