I've never really cared about this type of thing, but I agree, I've heard that it can, in theory, be used without committing a mortal sin.  However, a venial sin would be committed without a good need for it.

I absolutely know, and science proves, that cannabis oil is VERY good for you, especially for those with central nervous system disorders.

Yes, the "good need" or "sufficient cause" criterion can be a little slippery.  I've known people who have severe anxiety issues.  So if they felt that they were helped by smoking a little marijuana a couple times a week, I wouldn't fault them.  I see no difference between that and popping a xanax or some other sedative that a doctor could prescribe.  But because one has a prescription and the other doesn't, is that a morally relevant difference?  There's of course the aspect that we are also required to obey just laws, but I believe that the restriction of marijuana was done for political/economic reasons, and/or Puritanical ones, rather than for just cause.  Alcohol causes 100 times more problems in society than marijuana ... and it remains legal.

Would you PLEASE READ THE ENTIRE POST instead of grabbing a snippet out of context, for crying out loud?  

Just a couple sentences after the snippet you quote, I wrote:

I go on to say that this is not to justify venial but to set up the notion that with SUFFICIENT cause there's no sin at all.  Adelman-Jone lists "calming nerves" as sufficient cause.  So I keep using the case of someone who has issues with anxiety.

My point was to correct your saying that it "is only a venial sin", as if a venial sin is nothing at all - that was the point of my reply. Not sure what else should I have said to get *that* point across to you.

I agreed that when used for medicinal purposes then there is no sin - even if one of the side effects is the associated euphoria.    

I know several Traditional Catholics that smoke marijuana regularly and believe it to be perfectly acceptable. Women and men. Some of them even have small children.

Would it enlighten them to know that this place exists?

https://www.huffingtonpost.com/entry/judge-rules-against-church-seeking-to-offer-marijuana-as-holy-sacrament_us_5b437937e4b07b827cc30212

I cannot see what relevance the linked article has to these Traditional Catholics. It's not as though they are smoking for reasons of religion as claimed in the article:

[font=ProximaNovaSlim, Noto Sans KR, Helvetica Neue, Helvetica, Roboto, Arial, ヒラギノ角ゴ Pro W3, Hiragino Kaku Gothic Pro, Osaka, メイリオ, Meiryo, ＭＳ Ｐゴシック, MS PGothic, sans-serif]It is our fountain of health, our love, curing us from illness and depression. We embrace it with our whole heart and spirit, individually and as a group,” the complaint reads. [/font][/color]

I am aware that there are medical benefits from marijuana, as mentioned and claimed by previous posters. Marijuana should be allowed for the use of those who need it.
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My own personal experience with it was one joint almost 40 years ago. I felt no euphoria but I did experience distorted visual perception in that an article appeared to be further away from me that it was in reality. It I had no reason to use it except for curiosity and to be social.
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Also from my experience of neighbours who were regular and heavy users and commercial producers, (we lived in a so-called alternative environment as non-users) we were highly ostracised because we were not "one of them". There were a lot of paranoia and other mental problems which we believed to be a direct result of marijuana (ab)use.
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Certainly abuse of marijuana could amount to mortal sin, but that does not seem to be the case in the OP.
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Right.  The good news is that people don't need to smoke anymore and they won't have to worry about the immorality of getting high, in order to feel relief from a health problem.  Cannabis oil is now available which has no danger of losing your state of reason.  So, really, there's even now LESS of an excuse to smoke.
Though I've heard the argument that one can smoke to get a buzz just like one can drink a few beers.  It's a valid argument, in theory, though I can't say that with any experience.

Sure.  I've known (personally) more people hooked on xanax (prescribed for anxiety) than on marijuana.  It's far more addictive.  In fact, it's often combined with alcohol.  I sat next to a poor young lady on a flight (returning from a business trip), and she was clearly all strung out.  She admitted to me later that she was on the flight to go to a rehab center in my area and that she had gotten hooked on xanax and alcohol.  In addition, a co-worker of mine had his teenage daughter hooked on the same combo ... and she had to go to rehab.  But people don't think twice about the morality of popping a xanax (which can also mess with your head too) if it's prescribed by a doctor.  It's as if big pharma is also in charge of tuning our moral compass.

I don't see any morally relevant difference between drinking alcohol just to get a buzz and smoking enough pot just to get a buzz.  Now, those could be venial sins without sufficient reason, e.g. doing it a lot just for entertainment (as Jone cited) ... as long as you don't lose your rational faculties.  But if you have anxiety and stress, and either a glass or two of wine (or some part of a joint that gets you to the same place), I don't see any difference between the two.  PS -- I've never tried marijuana.