THC is a wonder drug and has myriad medical uses. The most important use is to relieve stress. Stress is living with physical or mental pain. Stress is not having an appetite due to chemotherapy or radiation treatment. THC is also useful for anxiety. I have rarely suffered from anxiety, but do know how debilitating and suffocating it can be. A third use for medical marijuana is for the pain associated with memories. All of us have memories that are difficult to think about. In extreme cases this is called post traumatic stress disorder and can even precipitate episodes of psychosis in some individuals. All of these properties derive from the chemical structure of THC and it’s interaction with receptors in the brain.

Note no nitrogen and only two oxygen, a very hydrophobic molecule.

Another important use of marijuana is for depression. I would estimate that about ½ of the people who suffer from depression would benefit from marijuana use. It is hardly surprising marijuana has so many psychiatric uses since it interacts with receptors in the brain. 

Smoking marijuana is not good for the pulmonary system. In a rational world we would have e-joints, analogous to e-cigarettes, electronic joints that dispense pure THC without combustion byproducts. See  http://en.wikipedia.org/wiki/E-cigarettes.  E-joints would reduce the pulmonary risk of using marijuana dramatically. 

David Martin Degner