Take Control of Security for Mac Users, Chapter 10: Prevent Data Loss and Theft
Most of the topics in this book address ways of protecting your data in one fashion or another. But in this chapter, we change gears to address two key pieces of data security — preventing loss and theft of your data while it’s stored on your Mac.
>Secure Empty Trash: Instead of choosing Finder > Empty Trash, choose Finder > Secure Empty Trash. Doing so causes OS X to overwrite the files (once), not merely delete their catalog entries.
How does that work with SSDs?
AFAIK due to the internal workings of SSDs it is not possible to overwrite data at a specific location.
It's true that SSDs work differently with regard to erasing data, but that doesn't mean SSD users are entirely out of luck. The effectiveness of secure deletion depends on the method used, and as far as I can tell, Apple doesn't publicize the method it uses in Yosemite.
Back in the days of 10.6 Snow Leopard, some researchers did testing on third-party SSDs that showed Secure Empty Trash left a good bit of data still intact. However, I haven't seen any data on newer versions of OS X or on Apple-supplied SSDs. It is possible (I'd say likely) that Apple is now using a better method, even if it isn't necessarily 100% effective.
All that said, it is extremely difficult to recover data from an SSD that has been deleted even without (an attempt at) an overwrite pass. It's far more difficult to do than with a hard disk. And, if you use FileVault, the problem goes away entirely.