Ok

thank you for being honest, bear with me - this is going to be a long-ish explanation (but i'll try to be as brief as I can)
first, i need to explain what a strain is...
Cannabis comes in 4 varieties: Indica, Sativa, Ruderalis - and Skunk...
your friend smokes skunk - hence that very strong smell. Skunk was bred in the 60's by the CIA (believe it or not) in their MK-Ultra experiments (mind control)... they did this by breeding sativa strains with indica strains to maximise potency... this gave rise to the term - skunk. Some of the famous strains the CIA bred that are still available in coffeeshops (in Amsterdam) today are G-13, C99 and White Widow.
These are known as strains - or types of skunk. There are many, oh there are a lot, and most have been bred for pleasure, not pain.
So when I mention strain, I am trying to narrow down what strain of skunk he gets from his dealer. Now here's the tricky part... most dealers don't even know what they are selling. they'll say, "this is cheese mate - and it's the doggs danglies, take it" - cheese is the strain he "thinks" it is, it could be a kush, or a diesel, or another - your friend just won't know - because his dealer didn't grow it. As it passes hands, the name changes too - to suit the prospective clientele, you see?
This is what i mean by - no regulation...
Now, there are literally thousands of cannabis strains available from seed banks. There are even seed banks in the UK, that sell cannabis seeds - the one I used to go to was the london seed center.
The strains he smokes are not medicinal at all - they are commercial strains. Medical strains do not hit the streets, they are not a viable option in that sense - people like the stinky stuff.
So here is the deal, there are a few strains he can try, and he should ingest them... but even here there is a clause. Now I hope you are ready because here is it where it all gets a bit botanical.
the actual substance that takes effect on the brain and the body is called THC, (tetra-hydro-cannabinol), this breaks down into complex cannabinoids, such as CBD, CBN and CBG.
CBD = determines whether it affects the body and in what quanitities - if the CBD content is 1% or higher, it can be classed as a medical strain
CBN = determines whether it affects the mind state, and in what quantities - if the CBN content is higher than 0.5% it will rock your world
CBG = determines the length of the effect - if the CBG content is over 1%, the effect can last hours, dependant on tolerance levels...
these are just 3 cannabinoids I have mentioned, there are plenty more... but for the sake of educating you quickly, I will just concentrate on these 3 for now.
Most cannabis today has these complex cannbinoids in varying quantities.
Now, let's say your guy got tired of buying from street dealers and actually managed to grow his own, and did his research into what cannabis strains are good for pain relief: what he will find is that no matter what strain he looks at for pain relief, he will still find that the the CBN content is there - which means that no matter how he takes it, he gonna get high... but there is a way around this...
When it comes time to harvest the crop, he need to keep a close eye on the trichomes... ooh, new word - trichomes.
trichomes are only visible thru a microscope (most growshops do pocket microscopes and they are pretty affordable). Trichomes are like stalactites with a ball on top - as the cannabis becomes riper, the trichomes go from clear, to cloudy, then milky then amber...
in order to stop the CBN from developing further, the plant must be chopped before the trichomes become cloudy, basically he must chop the plant when the trichomes are clear - this minimizes the risk of getting high. Infact, cannabis with clear trichomes is know in the industry as dud-bud, because it hardly ever gets anyone high.
But here is the tricky part, and where experience in growing comes in handy - you have to know your plants well enough to know when to flush them with de-ionised water, to leech all the chemical nutrients out of it, or this poses a toxic hazard to the body and will do more hamr than good. You see, the three main chemicals that the plants need are Nitrogen, Phosphorous and Potassium. no one wants those in their body, nuh uh... so the flush is necessary... the flush basically means replacing the water based feed with plain de-ionised water for two weeks to ensure all the nutes have been leached from the plant.
So let's say your friend managed to track down a good medical strain (for example - the White Russian), managed to set up his grow space and got all the equipment (this is not cheap) and the feeds (go organic) and managed to flower the white russian, and then catch it in flush as the trichomes were still clear, and then chopped it down - he will now have to dry it. Once dried (anything from 4 to 14 days dependant on temperature and humidity) he will now have to prepare it for medicinal use... now here is the really complicated part.
Real medical marijuana comes in oil form. he will have to do an ISO extraction, which involved using butane (highly inflammatory) to extrant the trichomes out of the cannabis, and then he will have to go thru the process to make it usable... if he can manage to go thru all this, and he ends up with some oil, he can now use this on his toast, or as a tincture (one drop is more than enough as it is ultra concentrated) ... this will provide very effective pain relief without affecting his mind.
Now, everything I have written here is a very brief summary of how to get true medical grade cannabis that does not get you high... but there is really, a lot more to it. I just touched on the main points. If I was to go into detail, I would approach a publishing house first.
If you have any questions, go ahead
Scimi