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How do THC and CBD relate to cannabis potency?
Please note, this article was written in 2008 and some of the information may be outdated. For the latest research and information that growers need to know about THC, CBD, and other cannabinoid levels in your marijuana, so you know exactly when to harvest, click here.
Updated Article: How Do THC, CBN, and CBD Relate to Cannabis Potency?
The two main components in the marijuana plant (that we know of) which cause its effects on humans are THC(Δ9-tetrahydrocannabinol) and CBD(Cannabidiol). Some people only pay attention to THC when talking about marijuana "potency" but the story is actually a little bit more complicated than that. As we are studying cannabis, we're learning that CBD actually plays a much bigger role in the overall cannabis experience than we originally thought. A recent study indicates that cannabis buds which are high in CBD do not cause the memory impairment which is normally cited as the biggest side effect of smoking or using cannabis. This is big news for patients who would like to use cannabis but do not want any memory side effects. It's becomming apparent that in order to understand the whole picture about the effects of cannabis, we will need to learn about both THC and CBD.
THC is the main psychoactive component in marijuana buds. THC appears to help relieve pain and is neuroprotective(helps keep brain from degenerating over time). THC mimics the action of anandamide, which is a naturally occurring cannabinoid in the brain. THC is thought to be the cause of the following effects of cannabis: relaxation, euphoria, altered space-time perception and appetite stimulation. What does it mean when marijuana buds are "17%" THC? It means that of all the cannabinoids present in the plant, 17% of them are THC. Having a high THC content by itself does not necessarily mean that the marijuana is great. It's important to look at the whole experience caused by the plant which includes another substance known as CBD. You want to find a strain and prepare your plants to cause the effects you're looking for.
CBD was once thought not to affect the subjective affect of marijuana, but further studies have shown that it actually does have an affect. CBD appears to relieve convulsions, some types of inflammation, anxiety, and nausea. CBD has also been show to help stop the growth of cancer. CBD is also effective as an anti-psychotic for people suffering from schizophrenia. Marijuana buds that have a higher amount of CBD are associated with a more sedative or calming effect. Cannabis buds that contain high amounts of CBD are a perfect treatment for insomnia or for treatment late at night.
The best results seems to come from using marijuana that has a mix of both THC and CBD. When used by itself, THC can cause disorientation and anxiety. CBD seems to prevent these effects. In fact, a new drug, Sativex, was recently released which contains 50% each of THC and CBD. Sativex seems to be very well tolerated so far and doesn't have many of the side effects associated with Marinol, which was made of 100% THC.
The cannabis strain that you're growing will largely determine the amounts of THC and CBD produced. The genes of a plant play a big role so it's very important to find a strain which has the effects that you are looking for. More and more seed banks online are offering information about both THC and CBD.
While not related to CBD, it is important to note that THC degrades into CBN, which does not have the medical benefits of CBD, but greater levels of CBN will help prevent some patients from getting anxiety, paranoia, and other "head-high" effects of high levels of just THC. While you cannot really affect CBD with the righ harvest time, you can affect the levels of CBN.
Some people prefer both kinds of cannabis and will harvest half the plant at one point in it's flowering stage, and then harvest the rest of the buds a few weeks to a month later. Some people like cannabis with high THC because it can be more 'up' or 'trippy' and therefore always harvest their buds on the earlier side.
The picture above shows a close-up of the trichomes of a White Rhino cannabis bud. The trichromes are a mix of clear and milky/white in this picture. You can also see that there are lots of new white pistils/hairs. Some people might like to harvest at this point. Personally, I would wait another month or so for the buds to mature before harvesting. I'm looking for at least some amber trichomes and all brown hairs. Buds which are harvested later (3-4 monthes into flowering) tend to have higher levels of CBN (NOT CBD) and are better medicine for relaxation and treating insomnia.
This page has more information about how to check the trichomes of your cannabis plant, as well as general harvest information.
I personally use cannabis for anxiety, and therefore I like to have high CBD & CBN levels in my buds. I always choose high-CBD strains and allow my plants to run their whole course before I harvest.
I strongly recommend doing some experimentation with different strains and harvest times to see what suits you best. I can only offer a general guide, but everyone's individual experience is going to be different.