Before doing shrooms, or any other drug for that matter, I researched the topic for hours upon hours. In all of my research I found that shrooms are physically the safest drug for your body given that you don't overdose or take such a high dosage you hurt yourself.
I never found any long-term damage effects from the use of shrooms in my research. Just be sure not to take high dosage, especially the first few times. I would start out with 1-2 grams or a little less. After a few trips you should stay around 2-4 grams until you get very used to tripping.
In my opinion shrooms are not worse than weed or alcohol.. in the physical sense. If you are of an unsound state of mind you may have your perspective on life changed, it could be for better or for worse. Your personality may change also, even after one trip. This usually only happens at high dosage, and these changes are more often found with LSD use.
Of course the best thing you can do is research it on your own. Check out as many websites as you can.. Pro-drug and anti-drug both. Just be warned that a lot of anti-drug websites give the effects of PCP, X, LSD, and shrooms as if they are one drug. So you are sometimes told the effects of shrooms are the same as pcp, x, and lsd. Also a lot of pro-drug websites show shrooms as begin extremely harmless, but realize they can cause physcological changes and bad trips.
Bad trips are hell. I have never had one on shrooms but I did have one whilst on LSD. It is my opinion that people usually only have bad trips when they think a lot about it or are scared of the drug. If you just go with the flow everything will be alright.
The psycological changes that are for the worse usually only happen during bad trips. If you find yourself beginning to have a bad trip there are ways to calm yourself. First off smoke some weed to calm your nerves. Remind yourself the trip will be over in a few hours and everything is just the drug playing tricks on your brain. You might also want to dry drinking a glass or orange juice. If worst comes to worst just take a couple of sleeping pills and you won't have to worry about the bad trip anymore. It is also good to have a friend with you to talk with you if you are having a bad trip.. trust me it will make loads of difference.
Hope this helps (=