Some say that if you hold in cannabis smoke for 5 seconds you will absorb 95% of the THC—they say 7 seconds for the CBD. They claim that after 5-7 seconds your lungs are absorbing the tar in the smoke… But is it true?
This question comes up frequently in cannabis forums across the Internet. Some will say that the longer you hold in the smoke, the stronger the effects; others will say that it makes no difference. Neither side has evidence to support their argument.
But here is another way to think of it. First, it is important to remember that what determines the strength of the effects depends on how big of a hit you take, not how long you hold it in. When you take a hit, cannabis smoke passes through your alveoli, and then cannabinoids are diffused into your bloodstream. The deeper you inhale, the more smoke that passes through. More smoke means more cannabinoids. Holding in the hit is secondary; holding in your hit will help expand your lungs.
Second, our lungs were not meant for smoke. Any type of smoke is harmful to our lungs. Besides the cannabinoids in cannabis smoke, there are tars and plant matter. Although it is in extremely small amounts, your lungs still absorb the plant matter and tar.
Now, Instead of smoke, imagine if it was vapor. Vapor is comprised of 100% cannabinoids, no plant matter or tar; the vapor that you exhale represents all the cannabinoids that you lose. The longer you hold in the vapor, the more cannabinoids you will absorb.
For the most part, the same goes for cannabis smoke. The longer you hold the smoke in, the more time there will be for the cannabinoids to pass through your alveoli and diffuse into your bloodstream. When you exhale. You breathe out smoke full of cannabinoids, cannabinoids that could have enhanced your smoking experience.