I wouldn't say it could completely impair your iPhone, but it's a possibility you may run into a few issues every now and then with apps/tweaks. The only thing I warn you about is your warranty being voided. Once you jailbrake, your warranty is considered "voided", but that is not the case. If you run into any problems with your iPhone while jailbroken, you have the ability to restore the device as long as it hasn't completely stopped working.

you can run yourself into a few problems but you can always restore it , the thing is its an iphone so I'd suggest keeping a back up of everything at all times

If you follow instructions right and use common sense then not so much can go go wrong although sonetimes you just can't avoid some problems. For most people they run into some issues and that means everythings over, they think that's it. Blank icons for instance, easilly fixed. If you are willing to spend a bit of time researching your problem then you almost always find a fix or solution. If you are meaning if it can cause physical damage then the answer is no.

Miner issues can include:

Blank icon (can be be fixed with a tap of a button)
Springboard crashing (If safemode is installed then you can easily resolve)
Specific apps crashing (just uninstall tweaks you have installed related to that app)
Freezing (if you wait then it normally comes unfrozen)
Random reboots (normally only you can cause this by messing with stuff that doesnt need messing with)
Off the top of my head I could only think of these. Obviously more problems can happen if you start messing around with coding etc..

-Turtle_Beach- wrote In any possible way could my iphone be damaged from jailbreaking? Please list the effects jailbreaking could have.

Ok if you do mess up you can just restore your device wich will get rid of everything and set back to factory settings, or you could back it up so when you restore it you can load it all back. If you have IOS 5.1.1 the newest version, download absinthe from green poison and it will do it all by it self, thats what i used and it worked just fine.

no not really some apps can take up a lot of space. if u run into anything bad just restore and dont download shady things

-Turtle_Beach- wrote In any possible way could my iphone be damaged from jailbreaking? Please list the effects jailbreaking could have.

Pretty much nothing, but I don't know if the codes being messed up count?

You can always restore, but I don't think it should happen. I've jailbreak for many years, nothing problem.

It'll void the warranty, but you can easily restore your apple device.

-Turtle_Beach- wrote In any possible way could my iphone be damaged from jailbreaking? Please list the effects jailbreaking could have.

The battery life can decrease rapidly, sometimes it has been reported that it becomes impossible to restore, so you have to have it jailbroken constantly, people report that they get various errors whilst restoring from a Jailbreak.

No it cannot damage your phone at all the worst that can happen is you having to restore.

InspiringGraphics wrote

-Turtle_Beach- wrote In any possible way could my iphone be damaged from jailbreaking? Please list the effects jailbreaking could have.

The battery life can decrease rapidly, sometimes it has been reported that it becomes impossible to restore, so you have to have it jailbroken constantly, people report that they get various errors whilst restoring from a Jailbreak.

That battery life thing is a total load of crap. Unless you have loads of tweaks that require you to use data and run 24/7 that won't be an issue. And if you have restore errors, YOU did something wrong. You must restore them in a certain way in order to not lose your data or even possibly brick your iDevice.