Potency

The evidence presented in this review allows us to conclude that Δ9-THC and CBD produce biphasic, dose-dependent effects on several physiological responses. The biphasic nature of cannabinoid effects highlights the need for a careful analysis of the dose ranges separating therapeutic from unwanted effects. Besides, Δ9-THC produces dependence and harmful effects, while CBD does not.
The available pharmaceutical formulations of these phytocannabinoids and related molecules have clear therapeutic effects; however, more research is needed to assure their efficacy and safety since their effects are complex. Several additional potential therapeutic applications, mainly for CBD, are being proposed which, however, still lack sufficient clinical and preclinical support. For this reason, caution is advised when using or prescribing cannabinoids.
Additional consideration deserves the fact that the ECS participates in the development of the central nervous system98. Therefore, the use of cannabinoid-based formulations for the medical treatment of children and adolescents experiencing brain developmental changes must be carefully examined, balancing the pros and cons of prescribing cannabinoid-based medications in every single case. Cannabis research field is expanding with the identification of new molecular targets, the characterization of undescribed phytocannabinoids, and novel findings related to the ECS99. In addition, consumption of synthetic cannabinoids as drugs of abuse represents a new challenge in addiction research100.

If you're smoking a joint to enjoy the psychoactive effects of THC, then you might want to know how much of the potent cannabinoid is in a typical smoke. Here you'll learn how to calculate the amount of THC in a joint and understand what percentage of the cannabinoid your body is actually processing. 
The weight of the joint (in milligrams) multiplied by potency/THC percentage equals total milligrams of THC. 
One gram = 1000 milligrams. 
Example: The difference between a half gram and full gram joint of the same 20% THC flower:
1 gram: 1000 mg x 0.20 = 200 mg
Half gram: 500 mg x 0.20 = 100 mg
If you'd rather skip the math equations, a modern joint may contain between 60 to 150 mg of THC or more, representing a sharp increase from the approximately 10 mg common in the 1970s. 
The above formulas tell us how much THC is in a joint, but they tell us nothing about how much your body is absorbing from the joint. According to Rae, this number will depend on several factors that differ among individuals. These factors include:

• Composition of the joint, i.e., ratio of THC to CBD
• How much THC is wasted in sidestream smoke which wafts off at the end of a joint without being consumed, unlike mainstream smoke which is what you directly inhale and exhale
• Smoking topography, aka your puff technique
• Bioavailability (the proportion of THC that is able to activate the brain, after being introduced into the body and entering the bloodstream)

Rae elaborated on the key components of mainstream and sidestream smoke, saying, “The ratio of mainstream to sidestream smoke produced by a joint is highly variable because of differences in puff techniques. There are several factors in an individual puff. The volume of smoke per puff is typically about 35 milliliters but can be as big as 55 milliliters (for context, the volume of a shot glass is about 40 milliliters). This volume is determined by the force and amount of time a person inhales.”
Mainstream smoke is also affected by the frequency of inhalations, as Rae said, “Puffing more frequently increases the amount of THC consumed in mainstream smoke, and thus diminishes the amount of THC wasted in sidestream smoke.”
Ultimately, bioavailability is calculated by measuring the THC in the blood, and comparing that to how much THC you started with in the joint. Referencing research published in 2007 in the journal Chemistry & Biodiversity, Rae added, “Bioavailability is highly variable for inhalation: experiments in humans show that it ranges from 2% to 56% depending on the person.”
To illustrate bioavailability, Rae provided the following examples using one gram joints and half gram joints.

• One gram joint = 200 mg THC. On the low end, 2%: 200 x 0.02 = 4 mg. On the high end, 56%: 200 x 0.56 = 112 mg.
  The bioavailable THC in a 1 gram joint with 20% THC is between 4  and 112 milligrams.
  Half gram joint = 100 mg THC. On the low end, 2%: 100 x 0.02 = 2 mg. On the high end, 56%: 100 x 0.56 = 56 mg.
  The bioavailable THC in a half-gram joint with 20% THC is between 2 and 56 milligrams

[1]. In 2018 Michigan legalized the use of marijuana for adults. Since this law took effect, increased availability and use of cannabis have led to an increase in emergency department (ED) visits, as well as complaints about the drug's neuropsychiatric effects [2]. High doses of cannabis can be associated with undesired effects such as paranoia, psychotic-like symptoms, and panic attacks, depending on the content of its principal active constituent, D9-tetrahydrocannabinol (THC), and that of cannabidiol, a constituent with anti-anxiolytic properties [3]. Higher concentrations of THC relative to cannabidiol, as demonstrated in many commercial products, are associated with increased incidence of psychotomimetic symptoms [4,5]. Various studies in adults with acute THC exposure have shown a dose-related reduction in performance at laboratory tasks measuring memory, divided and sustained attention or concentration, reaction time, and tracking and motor function [3,6-9]. Less is known regarding the acute effects of THC in the pediatric population, and much of the

data that currently exist involve retrospective reviews of large, coded data sets [10-12]. The purpose of this study was to describe the prevalence, clinical features, and disposition of cannabis neuropsychiatric toxicity in a community-based study.

In conclusion, our findings confirm previous evidence of the harmful effect on mental health of daily use of cannabis, especially of high-potency types. Importantly, they indicate for the first time how cannabis use affects the incidence of psychotic disorder. Therefore, it is of public health importance to acknowledge alongside the potential medicinal properties of some cannabis constituents the potential adverse effects that are associated with daily cannabis use, especially of high-potency varieties.

Cannabis potency has risen significantly over the past several decades, with available evidence pointing to an increased risk of Cannabis use disorder, psychosis, acute cognitive impairment, and structural brain changes with use of high-potency Cannabis. Clinicians should consider asking patients who use marijuana about potency to better assess risk of psychiatric adverse effects.

Marijuana is typically four-times stronger than it was a couple decades ago. On top of the boosted potency, since legalization, growers have been able to refine their skills to grow strains for unique and specific ailments. Not to mention the exploding market of concentrates and dab culture.

The simple fact that THC is fat soluble. That makes it absorbed in a very different way and much more difficult to relate behavior to, say, [blood] levels of THC or develop a breathalyzer."  The height of your intoxication isn't at the moment when blood THC levels peak, and the high doesn't rise and fall uniformly based on how much THC leaves and enters your bodily fluids, says Marilyn Huestis, who headed the chemistry and drug metabolism section at the National Institute on Drug Abuse.

"We found that frequent use of high-potency cannabis significantly affects the structure of white matter fibres in the brain, whether you have psychosis or not," 
The main psychoactive ingredient in weed, tetrahydrocannabinol (THC), is much more concentrated in modern skunk strains as compared to traditional pot and hash -- up 14 percent as compared to 4 percent.

Marijuana use by kids between the ages of 12 and 17 is 58 percent higher in Colorado than the national average, according to the RHMIDTA. The rate of use among college-age adults is 54 percent above the national average. Drug-related suspensions from Colorado schools jumped 34 percent from the 2005-2009 period to the 2010-2014 period, while alcohol-related suspensions stayed flat.
 "Everything they said would happen has not," says Gorman. "They said alcohol use would go down. Alcohol use went up. They said it would eliminate the (marijuana) black market. We are the black market. The trends show that legalization is not working."
 

The proliferation of foods infused or coated with THC has become a growing concern, even among some marijuana advocates. Several high-profile marijuana crimes and deaths involve consumption of edible THC products.
“When THC is available in food, it’s even harder for people to see it as a drug,” Lewis said. “But it is a drug. It is a depressant, a hallucinogen and an addictive substance that changes chemistry in the brain. Research shows all of the above.”

In old-school dope, levels of THC — the psychoactive chemical that makes people high — were typically well below 10 percent. But in Colorado's legal bud, the average THC level is 18.7 percent, and some retail pot contains 30 percent THC or more, according to research released Monday.
"This shows that marijuana is a GMO product just like other products sold by big business. And just like other industries, now you have a big marijuana industry determined to hide these findings from the public. Where is their outcry? Where are the promises to change the way they do business?" 

Based upon the foregoing evidence, this author has a clear preference for zero tolerance laws to deal with the increasing scourge of DUID.  The increasingly accepted Libertarian view is that such laws criminalize personal choices that cause no harm to citizens other than the drug consumer.  Laws requiring probable cause be first established before requiring a blood sample theoretically alleviate this concern, but are unconvincing to opponents of zero-tolerance laws.  Adoption of New Zealand’s approach is suggested as a means of gaining acceptance of zero tolerance laws without unduly harming Libertarian sensitivities.

The emerging marijuana industry in Colorado is trying to appeal to teenagers by offering cannabis-infused soda, chocolate taffy and jujubes.

The paper points out that the potency of marijuana has increased fourfold since the 1980s and can hardly be compared to the less harmful drug millions of pot smokers used decades ago.
And opponents point to Colorado and Washington, where the passage of medical marijuana in 2000 and 1998, respectively, were followed by the passage of recreational marijuana laws in 2012.

We welcomed in a new industry that knowingly promotes an addictive and harmful substance SO THAT PEOPLE COULD MAKE MONEY. The business of business is to make money and when there is money to be made people will signup no matter how messed up the means are. 
For these businesses to continue making the huge money they are making they will need to do two things: 1) engage new users, 2) convert current users to more frequent users.
Our weed in Colorado is so strong (20-30 percent THC in its smoked form) that we have a strain called “green crack.”
Our concentrates, which are advertised aggressively, are 80-90 percent THC, and are often smoked on a super-heated needle and puts the smoker on their back with one hit.  Our edibles come in gummies, fruit sodas, suckers, candy and yummy looking baked goods that are so potent that a single pot brownie in Colorado comes with a warning that it has to be cut into fourths before consuming.