Human beings have been selectively growing and genetically manipulating the cannabis plant for nearly three thousand years, perhaps longer, which makes it one of the first plants to be cultivated by humanity. In that time it has been bred into thousands of strains with a nearly infinite array of cannabinoid and terpene profiles. Cannabinoids are what make the cannabis plant unique, they are a set of chemicals with vast medicinal potential for human beings, animals, and the cannabis plant itself. Terpenes are the flavor and scent chemicals that give everything in the world its own unique smell and taste. There are only a few dozen terpenes, so the scent/flavor of something is created by a blend of various terpenes in varying amounts to create the scent/flavor profile for the particular strain of cannabis. Terpenes are related compounds to cannabinoids, and like cannabinoids they too have medicinal properties which they impart to their host plants and whoever ingests them.
The cannabinoid and terpene profile of a strain matters because that is what makes it unique; if Sour Diesel didn't have a lot of THC, CBG, myrcene, limonene, pinene, and caryophyllene it would not be Sour Diesel. Flavor-wise, the myrcene and limonene impart a sweet fruitiness which is balanced out by the more acrid, chemically combination of the pinene and caryophyllene. Myrcene has been shown to weaken the blood-brain barrier to cannabinoids, raising the potency of high amounts of THC already present in Sour Diesel. Pinene is a bronchodilator, which increases the effectiveness of the lungs and bronchial passages allowing the user to smoke or vaporize more Sour Diesel without irritating their lungs. This is what the Entourage Effect looks like in action; there is a strain with lots of THC, which has the psychoactivity and medicinal effects boosted by the terpene myrcene, and the overall effectiveness is improved by pinene soothing the lungs.
By paying attention to the cannabinoid and terpene profiles that work for them, patients can better know what sort of medicine to get in the future because they will know what worked in the past. For those who are not using cannabis medicinally, profiling matters because it lets you know what a strain will taste like and how high it will get you. The current research on cannabis supports the idea of using entourage-based therapies which take advantage of whole-plant medicine and using the combined, synergistic medicinal effects of the dozens of cannabinoids and terpenes present in the cannabis plant. One notable example is the use of CBD to calm the psychoactive effects of THC while preserving its beneficial medicinal effects on pain, nausea, and a host of other conditions.
All medicine is trial and error, even with pharmaceuticals there are no silver bullets where a drug will be guaranteed to work for everyone. That is entirely true for cannabis as well, there is no one-size-fits-all. Many people try to make generalizations about indica and sativa strains where often indicas are described as strains to make you sleepy and sativas are those that energize you, but these anecdotal views are not grounded in current science. Rather than talking about your cannabis in terms of it being indica or sativa dominant you are better off talking about the cannabinoid and terpene profile of that strain. Indica and sativa say more about what a plant looks like when it is growing than what its effects will be when consumed.
Every cannabinoid and terpene profile will have different effects on the user, potentially psychoactive but also potentially not if the strain is higher in THCa or CBD. Strains with higher amounts of cannabinol, CBN, will produce a heavily sedating effect; this could be responsible for the couch-lock feeling that some strains have. Every cannabinoid and terpene profile will produce different results and we are getting a better understanding of these results every day. Profiles that are heavily dominant in CBD, THCa, and CBG have been shown to be helpful to people suffering from epilepsy and other seizure conditions like Dravet or Doose Syndrome. As I have mentioned in previous posts, a balanced ratio of CBD and THC is ideal for anyone suffering from all types of pain, because both THC and CBD work to reduce pain through different mechanisms. CBD lowers the amount of pain felt and THC helps you forget that you are in pain; that means less pain signals are transmitted to your brain and when they are they feel less severe. People suffering from mood disorders such as PTSD, anxiety, or depression can see benefits from varying ratios, ranging from all THC to all CBD.