||"Shrooms" - more properly, psilocybin containing mushrooms, contain several chemical which are similar to LSD. The most active of these chemicals are called psilocybin, psilocin and baeocystin. The effects of these mushrooms are very similar to an acid trip, though much shorter. It is not very much like Ecstasy, which belongs to a very different family of drugs.|
Shrooms have been used by Native American healers and shamans for thousands of years as part of healing and spiritual rituals. They are among the safest drugs known to man, and have no significant long term effects on the body (including the back - I'm not sure what you think they do to it). They are certainly not deadly poisons. Most of the psychedelic mushrooms sold on the black market are grown in sterilized jars containing decomposing grains. Wild picked shrooms are rarely sold these days, so the chances of getting poisoned because you got the wrong kind of mushroom is relatively low.
It's important to know that most of the research into negative effects of psychedelics have grouped all of the psychedelics together, including LSD, Psilocybin, DMT, etc. Practically, most of these have actually studied LSD users, as LSD is by far the most common hallucinogen. Very little is known specifically about long-term psychological effects of psilocybin mushrooms, but following are descriptions the two most commonly reported negative consequences of psychedelics in general.
The primary consequence associated with psychedelic use is persisting anxiety and/or psychological disturbances after the effects of the drug have worn off. These are alternately referred to as 'flashbacks' and 'post traumatic stress disorder'. These effects are relatively uncommon and occur most frequently in people with pre-existing mental or psychological problems (which may or may not have previously manifested). They are also more common after heavy use or high doses.
A secondary consequence reported by users of psychedelics is something now referred to as 'post hallucinogen perceptual disorder'. This is a complicated and poorly understood subject but a small percentage of 'hallucinogen' users report long lasting changes to their visual field, including increased sensitivity to movement, patterning in low light, etc. Some people find this disturbing while others do not.
You are smart not to take them just because your friends say to. That is no reason to use drugs. Psychedelic drugs can be very powerful therapeutic aids and spiritual tools for self exploration, personal growth, and creativity enhancement - when they are used wisely, in moderation, and by someone who has prepared and educated themselves. They can also be a great deal of fun sometimes. Taken recklessly by people who aren't prepared, however, they can lead to horrifying experiences ("bad trips"). These substances should never be taken because of peer pressure.
The big issue is that you are 17. Psychedelic drugs can open wonderful new doors for you, letting you explore the universe and yourself in amazing new ways. They can lead to deep personality changes. However, you should wait until your personality has fully matured before you go trying to explore and change it. At 17, life's routine daily pressures are stressful enough. If you are curious about psychedelics, read some of the excellent books and web sites out there on the issue, and educate yourself. It's extremely important to feel that the time is right for you before trying a psychedelic drug. Any anxiety or misgivings you may have could potentially be magnified during a trip. Maybe in a few years the time will seem right to consider experimenting.