Pot use? Not particularly. Addictive substances make children more susceptible to other addictive substances, and the younger the children, the easier it is for them to become addicted.
Before brain maturity, anywhere from the age 19-25, exposure to addictive substances may actually permanently affect the development of the brain, making them more susceptible to addiction, and harder for them to break an addiction. Plus, it is now known that if children become addicted to one thing, it becomes easier for them to become addicted to other things.
This is not entirely chemical addiction either. Behaviors such as gambling and other obsessive/compulsive behaviors fit into this paradigm. And addictions are subdivided into both psychological (PSY) and physiological (PHY) effects.
1) Stimulants. Strong PSY dependance, weak PHY.
2) Sedatives and hypnotics. Mild to strong PSY, severe PHY.
3) Opiate and opioid analgesics. Mild to severe, both.
Importantly, substances like caffeine and nicotine are part of this picture, and are rated far stronger than marijuana for their addictive effects.
The bottom line is that there is no direct linkage between marijuana and other drugs; except for the *social* link. That is, if you are in a group that obtains and uses marijuana, they are likely to be involved with other behaviors, some of which are addictive, and some of which are just foolish.
I don't think gambling or OC disorders are going to land you in a hospital which just a little use.
Same can't be said for hard core drugs. Most hard core drug users started with pot use. Sure, the social circles are the usual introduction. Which is why they should be discouraged, not encouraged.