&gt;  Is there any legitimate research into this?<p>Tons - there are over 70 cannabinoids last I checked (which was several years ago, and we&#x27;ve discovered more since). They all have different effects. Some aren&#x27;t even psychoactive at all.<p>The indica vs. sativa is a rough way of describing the relative ratios of the various cannabinoids. Not all indicas and sativas are the same, and some sativas might be more sleep-inducing than some indicas, but it&#x27;s easier than enumerating chemical compounds which have rather unfriendly and unmarketable names.<p>&gt;  How do you know which is which?<p>Ask the person growing or selling it to you. If you live in a medical or recreational state (Colorado, California, etc.), they will be labeled as pure indica&#x2F;sativa, or a hybrid (and if a hybrid, which one is dominant).