When it comes to the subject of addiction and cannabis there are numerous problems that cloud the issue. For one thing addiction is poorly defined and the argument over whether or not cannabis qualifies as "addictive" is significantly affected by how you define addiction, with mental addiction easily applying to anything potentially habit forming including any and all activities and substances, including of course cannabis. Physical addiction, which itself is poorly defined, is a different issue and while there are some potential arguments for also incorporating a wide range of physiological effects that a substance can have as the deciding factor in qualifying something as "physically addictive", the sort of physical changes that your body goes through as a result of chronic use from substances like heroin, nicotine, alcohol, even caffeine do not apply to cannabis in quite the same way.
For one thing cannabis produces Endo Cannabinoids that are virtually identical to the Phyto (from the plant) cannabinoids, particularly when concerning their interaction with the Cannabinoid Receptors in our body.
In addition to this, the cannabinoids we consume store in our fat and do not dissipate quickly like their "Endo" counterparts. So while cannabis cannot be completely ruled out as potentially addictive, by a certain standard and definition of the term, there are numerous reasons why physiological dependency does not apply to cannabis in the same way as other substances and why withdrawal symptoms from cessation of use are rarer, milder and in many cases and for many people non existent. 

But another issue that is seldom considered when having the conversation about cannabis and addiction is the potential to confuse addiction with medical need.

For example, and this could be true with numerous medications, if a medication is being used to treat a condition, especially the symptoms of a condition, and the medication is ceased the patient will likely experience negative effects. Symptoms that could easily be interpreted as withdrawal symptoms resulting from an addiction to the drug could actually be the onset or recurrence of symptoms that were previously being kept away by the drug in question.
This is all the more likely with cannabis because cannabis has so many medicinal applications, including numerous significant effects on relieving the symptoms of illnesses, and so few side effects (with no established harmful effects).

Also the potential for any type of "withdrawal" is limited by numerous factors.
Most people who stop using cannabis notice virtually nothing in the way of withdrawal, those who do experience anything that may qualify as a withdrawal symptom find themselves to be slightly less patient, slightly more irritable as there is a potential for Endo Cannabinoid production to be lessened as a result of chronic and heavy cannabis use. This would likely be because cannabinoids from the plant, like THC, can fulfil the function of Endo Cannabinoids like Anandamide. This would mean that the signalling process requesting Anandamide production may be less busy as a result of THC fulfilling the need, when THC consumption stops then the signalling will resume and more Anandamide will be produced but there can be a slight delay and the transition from having your cannabinoid requirements met by Phyto Cannabinoids to Endo Cannabinoids may involve a drop off that can lead to mild symptoms of irritability.
In addition to a potential physiological reason for this there is also the more obvious drop off involved in the fact that even when Endo Cannabinoid production returns to optimum your body, in particular your brain, is still not saturated to the same euphoric level that you would be achieving with your consumption of plant based cannabinoids, in particular THC. So even with an instant return to optimum Endo cannabinoid levels many people may not respond well emotionally to the drop off, simply because they have become accustomed to higher, more euphoric, doses of cannabinoids in their brain and even optimum Endo cannabinoid levels pale in comparison. 
Though this is also an example of where an underlying condition may be evident and people who struggle to deal emotionally with out the high levels of cannabinoids may be suffering from some serious emotional or psychological problems which cannabis is medicating to the point of masking such symptoms.

The potential for cannabis to mask symptoms that can resurface when cannabis use is ceased is especially likely when dealing with mental illness. But even outside of such conditions the medical potential for cannabis means that cannabis can provide tremendous relief and therapeutic benefits which can mean that stopping cannabis use can result in the onset of symptoms which, as opposed to some result of addiction, are in fact symptoms of the illness that cannabis is treating.

So while addiction cannot be ruled out, even when talking outside of simple emotional dependencies, it is important that we do not confuse substance addiction to cannabis with an actual medical need for cannabis to treat an illness.

By Michael Sanderson