Seasonal share prices?

Hi All,
First post here...
Been lurking for a couple of weeks, Still havent invested anything yet, although playing the ASX Sharemarket Game for a bit of experience first.
Trying to read up on FA and TA as much as possible but very little experience/knowledge as yet.

Anyways, first question to the board...

Are share prices influenced by seasonal changes? (time of year/month)

I know alot of organizations have much higher profit margins leading up to christmas to example (I work for a Pharma company and we make alot more profit over spring summer suplying drugs for european winter) so does these higher seasonal profits influence the share price?

Would be a good study for a research student I guess.

I'd hazard a guess and say perhaps retailers like JBH, DJS might rally into Dec
I think there is some seasonality in Apple in the states.

Funny, I was actually thinking about this during the day today.