Like all good things, the potency of a cannabis product will eventually come to an end. THC is a perishable compound, and factors such as light, temperature, and air contribute to its rate of degradation.  Even if you don’t understand why, you have probably heard that cannabis should be stored in a cool, dark place. We’ll get into the science behind that in a moment, but in general, that is the right idea when it comes to protecting the integrity of your cannabis plant’s cannabinoid content.

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No matter how well it is stored, THC levels will eventually decrease.

A 1999 study found that over time, THC levels decreased while CBN levels increased in properly stored cannabis plants. The study placed dried plant material in closed barrels contained in a ventilated, dark vault. The temperatures were relatively stable, fluctuating between 68 and 71.6℉. To measure the rate of degradation, researchers collected samples from the barrels annually over the course of four years.

Cannabis loses thc while in storageThe study found that after one year, THC content decreased from its original amount by an average of 16.6%. After two years, it decreased from its original amount by an average of 26.8%. After three years, it decreased from its original amount by an average of 34.5%. After four years, it decreased from its original amount by an average of 41.4%. These percentage changes suggest that THC degradation is most extreme in the first year, but tapers off to an annual decrease of about 7% in the following years. The results also seemed to implicate high THC levels have a quicker degradation rate—the more THC in the cannabis sample, the quicker it degraded in the first two years.

Given this research, you should expect your flower to eventually lose its punch. Of course, there is not a universal rate of degradation since every cannabis strain, flower, and storage environment are different. Some flower may last much longer than others.

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This is especially true if the storage environment is cool, dark, and dry (not arid, but not mold-friendly either).

The 3 Fastest Ways to Degrade THC

If you want to protect the integrity of the THC content in your cannabis product for as long as possible, do not follow these steps. In fact, exposure to heat, light, and air is the quickest way to transform your aromatic medicine into bland waste.

1—Place it in direct sunlight.

Direct sunlight causes thc degradationAs with temperature, light instigates a biosynthetic process in a cannabis plant that results in the deterioration of its cannabinoid levels. Since 1971, the scientific community has been aware of light’s effect on the degradation of THC. A study published that year concluded that the best storage method for cannabis was under nitrogen and in the dark. A few years later, 1976 research examining cannabinoid stability over the course of two years found that light exposure was the most effective variable at depleting all cannabinoid levels, including THC’s.

This was particularly apparent in samples of cannabis oils, a form of the plant that is more volatile than cannabis flower.

2—Leave it out in the open.

The air we breathe contains a number of oxidizing agents, oxygen being the most prevalent of them. When cannabis is exposed to oxygen, a reaction at the molecular level causes the plant’s cannabinoid structure to change. 

The same 1999 study that determined the ate of THC degradation over a 4 year period found that the deterioration of THC correlated with an increase in cannabinol (CBN) levels. That’s because when oxidized, THC converts to CBN. The study found that after one year, the ratio of CBN to THC increased by 2.5 percent. After two years, it increased by 6.7 percent. After three years, it increased by 9.4 percent. After four years, it increased by 14.2 percent.

CBN is a non-psychoactive cannabinoid that, while indicative of old weed, has some therapeutic utility. In fact, CBN is believed to play a significant role in the sedative effect cannabis has on users. This makes it a viable treatment for insomnia. Additionally, CBN exhibits antibacterial, anti-inflammatory, appetite-stimulating, analgesic, and glaucoma relieving attributes. Given that the only way to get CBN is through the oxidation of THC, this may be the one incentive you have for actually expediting THC’s degradation process.  However, CBN is far less potent than THC and CBD, both of which possess similar therapeutic abilities and can achieve them in smaller dosages.

3—Expose it to high temperatures for a long period of time.

Don't expose your weed to heat for extended periods of timeIronically, heat is also an essential ingredient in the synthesis of THC. Raw cannabis flower does not contain THC.  Instead, it is loaded with THCA, the acidic, inactive precursor to THC. THCA does not produce the cerebral effect that THC does. While it is possible to get high by consuming raw weed, it would take an exorbitant amount to do so.

THCA synthesizes to THC during the process of decarboxylation, or the exposure of weed to heat for a certain duration of time. Cannabis and Cannabinoid Research published a 2016 study investigating the precise length of time and temperatures for the most efficient decarboxylation processes. According to that research, all THCA was synthesized to THC after the raw cannabis had been heated at either 110℃ for 30 minutes, 130℃ for 9 minutes, or 145℃ for 6 minutes. However, as soon as decarboxylation was completed, THC levels began to degrade.    

In 2004, the Journal of Analytical Toxicology published a study analyzing the effect of temperature on THC’s stability over time. The study used THC-spiked and authentic urine samples to gather its results. The researchers found that when stored in temperatures over 4℃, THC levels initially increased between 2 and 15 days. This is likely because the temperature caused THCA to synthesize into THC. However, after 15 days of storage in 20℃, THC levels began to taper off.

The study suggests that the best temperature to store cannabis in is at about 4℃ (39℉). However, never freeze cannabis flower. Once frozen, the resin-rich trichomes become brittle and can break off.