pipe

I'm new to this site, and new to pot as well...I just turned 15 a few weeks ago, and I got stoned for the first time a few days afterward. If the research I've done is anything to go by, marijuana is a pretty much safe drug, with the only real health problems being when you smoke the plant, cause it might cause light lung problems later in time.
Anyway, from what I understand, its a bad idea for adolescents to use pot, as it might somehow interfere with growth. Assuming I get stoned somewhere between once a week and 2/3 times a month, is there any real harm ? I'm new to this, but due to the risk of getting in trouble + the fact that its hard/costly for me to obtain pot, I'm planning on keeping my use limited to just a few times a month. So, my question is, would this light use affect my growth considerably, or would the effects be minimal/virtually nonexistent? Any help with this would be much appreciated...