A thread regarding behavior under different types of alcohol got me thinking if the same was true about weed. Some people claim that red wine makes them sleepy and beer makes them sloppy when in reality alcohol is alcohol and its our mind trying to fulfill the stereotype. I admit that setting has a lot to do with it as well. THC is THC right? How can different strains make you different types of high? I ask this because industry behind it is huge, and if THC is the chemical that gets you high how can different strains effect you different if its all just THC even though they make visually look different?
Yes and no.
THC is THC. But dosage and concentration can cause wildly different qualitative experiences. There is also the issue of taste and circumstances. Different strains of pot have different appearances and flavor. Some is brown, harsh and tastes like dirty ashes. Some is bright green with red hairs, smooth and tastes like a Christmas tree. Surrounding yourself with friends and music is likely to cause different feelings than smoking pot alone in front of the tv. It is no different than alcohol in that respect: alcohol is alcohol, but flavor, concentration and environment will introduce a wide variety of different subjective experiences.
Sure, THC is THC, but what about all the other stuff you’re combusting along with it that could vary plant to plant?
Well, just of the top of my head, there’s no way of measuring THC concentration without lab equipment, and that can vary a lot between strains. So for someone who doesn’t read High Times religiously, different plants would give you different highs, as self-evidently as red wine and Everclear get you different kinds of drunk.
Also, Wiki sez that marijuana contains multiple psychoactive cannabinoids, so it’s still possible there’s something to it, even if you had an effective way to control the dosage.
Synthesized THC (tradename marinol) supposedly doesnt give the same effect as getting it from a plant, so there’s more going on than just THC. Its kind of like drinking different types of coffee or different types of liqour. Sure, its all caffeine or alcohol but the reaction people get is not strictly one based on concentration.
For instance, we know chocolate has sugar which gives us a slight buzz but we also know it has theobromine which is a stimulant and perhaps even a mild aphrodisiac. If you just fed someone sugar then they would not get the same effect.
Stoner here. There are more than one hundred different psychoactive compounds in Marijuana, each with a different effect. They can be present in different ratios in different strains. Some weed will put you to sleep, some weed will make you feel more alert, etc. All weed is different. Just part of the fun. 
There is cannabis sativa, which is what most people in the US and Mexico smoke, and cannabis indica, which I understand is common in India, Europe, and the Middle East. Sativa will make you tired and lethargic if you smoke too much of it, while indica will give a “clearer” and longer lasting high. I don’t think it’s a question of THC content, the high you get from each type is similar, but different enough that someone who knows his weed can tell what type it is just by smoking it.
There are many different strains of each type, but the difference between the two types is greater than the variation between different strains of the same type.
I saw an interesting documentary on BBC America, called “Should I smoke pot?” or something like that. It featured a female reporter interviewing scientists of varying types about marijuana, and also a trip to Amsterdam where she sampled several different kinds on camera, and reported her experiences. She had different reactions to different types of pot. She liked the less potent varieties better, as it made her happy/giggly. The stronger stuff knocked her socks off, and may have scared her a bit.