Marijuana use dramatically increases risk of dying from heart attacks and stroke, large study finds

[Bernardo de La Paz]

79. Decarboxylation. For best results, decarb before cooking, to ensure decarb, though some cooking methods don't need it

Decarboxylation proceeds faster at higher temperatures, but there are practical limits to that. Likewise, longer time is more complete than shorter time, but there is little or no benefit to exceeding certain times.

The plant produces THC-acid (THCA) and a bunch of other cannabinols and related compounds. The plant form has carboxylic acid -COOH in the molecule. Heat over time makes it give up CO2, leaving a hydrogen where the COOH was. The result (THC) is the potent form.

A good starting point might be 40 minutes at 250 F, or 50 minutes at 240F. Interestingly that fits well with brownie cooking temperatures and time, bearing in mind that heat penetration does not equal the oven temperature. One site wrote up an (amateur scientist) experiment they did with ground cannabis in various oils in closed containers in boiling water baths (212 F) for four hours, with no prior decarb. They sent the results out to independent labs for assays. Spoiler - Olive oil, avocado oil, and clarified butter all did about the same with olive oil in the lead. They also did a batch boiled in a bath for 8 hours, double, and found no increase in THC.