LOL it's just pot, not heroin.
Maybe try some one day you might like it. Vaporize it, that's how we do it these days, better for your lungs.
Remember, cannabis is one of God's plants. There is no artificial substances involved. You are consuming a natural herb and getting a bit high that's all. Not dangerous in moderation. Sugar is worse.

OMG.why isn't Mason doing jello shots, drinking beer , and reading his Bible like NORMAL Texas kids?
That marijuana makes you WEIRD.

But I am curious as to why Mason as an individual takes them. Are we meant to understand why? It is never elaborated on. Perhaps it is his unstable family background, or the type of people he mixes with? Is he trying to fit in, or fill an empty hole in his life? Or does he just think it's cool?
Maybe he smokes pot because he likes the way it makes him feel?

@highland_lassie, I completely whole heartedly agree. Not of the fan of the movie like I thought I would be however, the choices that the fictional kids made is a little sad and does send out a wrong message to the real world

yeah, basically Mason is an everyday-cliche-boring-rebellious american teenager that we've seen a lot in American movies. Taking drugs, smoking, courting girl, out-of-wedlock sex whatsoever. I dont even know if this culture or style of life is real or just exist in their movie.
THRILLER IS MY FOOD!

thumbs up

I might be late to the party, but most people smoke pot because to make it easier to put up with the ignorant ramblings of people like Highland Lassie.
"I have Mountain Dew or crab juice."
"My god! That's disgusting! How could you even offer that to me! I'll take a crab juice."

This. If he'd been shooting heroin or snorting coke, I could see the OP's point. But drinking a beer and smoking some pot here and there should not be shocking to anyone, nor does there have to be some major life trauma behind it happening. It's fairly standard teenage behavior, at least where I come from (New York). I got drunk for the first time at 14, in the presence of my father, although without his initial knowledge; I was sneaking wine on the sly during a family vacation. Eventually it became obvious by my behavior that I was a little tipsy and I was found out, and the adults, including my father, actually found it rather amusing. (I doubt, however, that they would have been so amused had I come home in that state, rather than it happening in a safe place surrounded by family and friends.)
I was also 14 when I smoked pot for the first time. It was just what was being done. In my later teenage years I hung with some kids who did much more hardcore drugs, including heroin and PCP, and observing them and their experiences was enough to keep me from ever touching those substances. It was only ever weed for me at least until my 20's, when I experimented with hallucinogenics and cocaine; the whole "gateway drug" thing is drug war propaganda, nothing more. Plenty of people who smoke pot never do anything else. It's just a recreational drug - like alcohol, only with far fewer negative effects or consequences.
The further a society drifts from the truth, the more it will hate those that speak it.

I think you're a little out of touch with reality. Marijuana is on the fast track towards legalization. The out dated rhetoric aside, its still cool with kids, and its not a gateway to anything.
Mason's recreational marijuana use is really no big deal, even his mom agrees.
I thought that might have been a peyote button Mason chomped down on there at the end, after all, they were in Big Bend county.

OP:
Which kind of leads me on to something else.when Mason is an older kid, he seems to choose friends that are not that nice, and his first serious girl friend, Sheena, turns out to be shallow and bitchy. Whereas he is generally a good guy, less rebellious than his sister, and polite and responsive to his new step mum and her parents, like when they give him a Bible for his birthday even though it's not the type of book he'd normally read.
If you paid real close attention to Mason's responses to many situations, he often said OK to whatever it was in a lack luster sort of tone. By that I mean he wasn't really excited or into anything, he just drifted along with the flow. He was a space cadet, dreamer and deep thinker long before he toked his first doob. He was like everyone else growing up in the sense that he saw or heard something and wondered how it worked or why it happened. Sometimes he made an assumption other times he asked someone for an answer.
Remember too that at the very first his mom picks him up from school he is already a product of a broken family. We don't know why his parents were divorced or if he was traumatized because of anything he saw and remembered during those years from age 6 backwards. It must not have been something viscous because she seemed to get along with her ex enough to allow him to come into her house and pick up the kids. Never mind whatever the court decree stipulated as far as visitation and child support payments as that usually causes trouble.
My response to your question about him choosing friends may be that they chose him. Remember he was a new kid in town a few times. Maybe they were bored with their lives and wanted to see what the new kid brought to the table. In this case it seemed to be nothing. But because he just went along quietly and was agreeable so he was accepted.
Think about the sorority girls Sheena pointed out and talked about pledging. That was what she really wanted. Mason didn't know what he wanted other than to create art with photography. His guidance from his blood father was basically just the fun stuff and he never had to deal with the day to day homework and chore issues that the two step fathers and mom did. That is the way many kids are raised in these modern times.
The bigger issue is why did the mother seem to keep picking drunks as lovers and later marrying them. No one knows what is in the mind of anyone so we all have to think about our needs of someone with a job to pay bills vs our wants for a good looking sex partner. And if a woman has kids, the replacement dad has to be given some leeway as far a discipline is concerned. Mason senior hit the nail on the head when he said women are never satisfied. He didn't say ALL, but implied it and ALL is almost never true. Many men seem never satisfied as well. Both replacement dad's seemed to be bored with the mom and their lack of importance in her or their own day to day lives. Maybe they had their moment of clarity before she had hers.
Your point about his gift bible not being a book he would normally read, they said it was his first bible. Mason and his sister went to church with the new in laws of there dad's after he got the gift. It was not shown if his mom ever attended church with them. So maybe he did not have any real moral standards to go by and thus missing the quality friends you believe he should be meeting.
Maybe the mom had already discovered that there is plenty of hypocrisy within church going people she knew growing up, it is just shown.

Just try to stay alive and see what the next minute brings.

There need not be some hidden issue the pot smoker is trying to deal with.
Exactly, the OP seems to believe the propaganda of public service films or what ever else they were taught about pot smoking as a gateway drug. Choosing not to participate in any social activity is fine if you think it is wrong or risky to your future.
I agree with all of the other folks who have said that his observation of others who have smoked and their behaviors lead him to believe it was not that big of a deal.

Just try to stay alive and see what the next minute brings.

Yeah, doesn't really change what I typed.

You do realize this movie was made by the director of Dazed and Confused, right?

lots of teens smoke pot for no reason other than to feel good. There need not be some hidden issue the pot smoker is trying to deal with. They see and hear other kids talking about feeling good from it and they are curious.
His character didn't look like he was abusing pot or alcohol at all, just a pretty typical American teen experience.

If she didn't care, she woudn't have asked him. She cares, but she was not interested in making a scene.
She says "talk in the morning."
Here is the scene, btw:

All the above reasons plus, his mom at least (who he lived with most of the time) didn't seem to care. She had some event at her house, maybe it was the Thanksgiving get-together, when she asked him if he'd been drinking and smoking, and he said a little to each question, and she just let it go.
www.freerice.com

"What makes me curious though,is why Mason in particular took drugs (I know he wasn't a regular drug addict or anything), but why he experimented with them..Peer pressure? His family problems? Or that HE thought it was cool, or was a bit of a rebel?"
Why does it have to be something like that? He did it for the same reason(s) any teen does. He was curious, he isn't strong enough to say no, he doesn't feel like it's a big deal, he likes it. This was not an exciting movie. It wasn't adventures and big moments. It was a normal kid having a pretty normal life. At least a little pot is a part of that for a lot of kids. That's all there was to it.
Bucka bucka, Enzo wife yucka.

I'm not sure why seeing Mason getting high is so surprising. I think I'd be surprised if they tried to push him off as a straight-laced kid who didn't experiment. Why do most kids, teens, adults, etc. get high, wasted, or whatever? More often than not, to escape reality, numb out the pain, as a social relaxant, etc. Mason had very little consistency as a child, and he was rather reserved. Those factors, in addition to many others, are often associated with substance abuse. Mason was all about experience, living in the moment. He was an artist.

What makes me curious though,is why Mason in particular took drugs (I know he wasn't a regular drug addict or anything), but why he experimented with them..Peer pressure? His family problems? Or that HE thought it was cool, or was a bit of a rebel?
I know a number of teenagers do experiment with drugs, so I'm not saying that showing teen drug use in a film of somebody's life is in itself unrealistic. But I was left a little confused as to why Mason did it. I'm thinking perhaps it was his troubled background, but I could be wrong.
When he mingled with adults, e.g. when his mum invited friends over, and when Mason Snr took him to meet the new in-laws, Mason Jnr was always polite and accepted their kindness. And he didn't bitch or laugh about them behind their backs. He just takes it all in his stride, like when Mason Snr's in-laws give him a Bible for his birthday. Not the kind of book he would normally read, but he politely accepts it as their way of being nice.
So he's not an out-and-out rebel, obnoxious or delinquent. But his pre-university friends as a teenager (bar Tony) are loud-mouthed and brash. I think the two seniors at the camping night are bullies and degrading towards women. Then the guy who drives him home just before his 15th birthday (the same guy from the camping night?) starts mouthing off and getting balshy, and then hands Mason what we know is more than just a standard cigarette.
I noticed at the camping night that Mason is relatively quiet when the other boys brag about their sexual exploits and pick on Tony. I'm just wondering why he seemed to choose really rough friends in high school. I went to a number of different schools due to my parents moving about, and even in the not-so-good schools you had at least a minority of kids who weren't rough.

Also, up until his girlfriend bailed, she genuinely seemed to care about him. The dumping scene caught me offguard. She did become a shallow bitch but a little too fast IMO. MJ had his heart broken which sucks no matter what age you are, but inevitably we all fall in love again as Mason Sr. points out correctly.

MJ was already an occasional toker before the brownie scene, bit not a 'pothead'. Weed aside, I think the end showed he had acquired the best of both parents. He was bright, grounded, caring, passionate, talented, had a sense of direction.

Smoking weed or having tried it is pretty normal these days. Just like alcohol which is actually way more harmful than cannabis.

It's legal in my state, have about half a dozen pot stores within walking distance of the house. It has the opposite affect of what You'd think.I don't see how the places stay open.

I agree with the OP. The recreational drug use by the character without any context just normalizes the behavior and sends out a bad message. Actually, the recreational activities of a lot of the kids' behavior sends a lot of bad messages and speaks more about the directors thoughts about the world which isn't the most responsible.