One thing that it's important to remember in the marijuana community is that some people have a problem with marijuana. That doesn't mean that pot is a problem, but it can become part of someone's self destructive behavior. Just like ice cream isn't a problem in itself, but for a person struggling with over eating it can become a tool they use to damage themselves.
Substance abuse and all forms of self destructive behavior are serious problems for people around the world. There are many reasons people get trapped or become addicted to behaving in a way that is bad for them. Marijuana is not physically addictive, thusly marijauna addiction is never really about pot. The real problem is usually a complex part of that person's life.
Drugs like cocaine, alcohol, and cigarettes are physically addictive. What that means is that our bodies and our brains become chemically dependent on those substances. If you try to stop using those types of drugs, your withdrawal can be accompanied with mild to serious health affects. The more toxic drugs can actually be fatal to quit without medical assistance.
Marijuana is not like that. Addiction to marijuana is more like addiction to things like, video games, food, gambling, etc. Unfotunately this doesn't mean that the addiction is any less damaging. It can still waste lives and ruin relationships.
"How do you know if you are addicted", is the most obvious question. The best way to tell is to take a second to examine your life. Is buying or smoking weed getting in the way of other important goals you have. Is being high all the time making it hard for you to accomplish important tasks. There isn't always an easy way to tell, but if you're honest with yourself you'll find an answer.
If you don't think that you can handle answering the question yourself, there are a few ways to find out. First try taking an extended break. If you can go for a month without smoking pot you're probably okay. If you can't you might want to think about looking for help. One way to get help is to get a psychiatrist. Unfortunately many psychiatrists today won't see patients who admit to smoking pot.
Another way to get help is to find a rehab center. Some of these places are a little too anti-pot, but if you need a break badly, they can get the job done.
Stoners aren't addicts. There are large numbers of very productive and happy people who smoke weed everyday, some multiple times a day. Remember there's nothing wrong with wanting to smoke pot, but if you're substituting important areas of your life with being high you might be missing out.
The 12 Step Program - 12step.org
Finding a Therapist - PsychologyToday.com