While yes they are harmful effects to smoking I believe that it has it's benefits as well. As with any state-changing technique or substance it is best used responsibly and for a higher purpose than just getting "************ed up".
Not to say that's not a good purpose for them every once in a while
But truth be told, mediation in combination with altered states is very intense, powerful and spiritually moving. Almost all major religions use or have previously used drugs to enhance the spirtual experience. We however msut use these responsibly for one and two we must use these as a means...not an end.
Smoking weed is great, but smoking with the purpose of worshipping God on a higher level and with greater enthusiasm is key to the whole process.
It is when we treat drugs as a god instead of a gift FROM God that they becokme dangerous and unholy.