Physical Effects

The study found that a number of brain disorders and behaviors predicted accelerated aging, especially schizophrenia, which showed an average of 4 years of premature aging, cannabis abuse (2.8 years of accelerated aging), bipolar disorder (1.6 years accelerated aging), ADHD (1.4 years accelerated aging) and alcohol abuse (0.6 years accelerated aging). Interestingly, the researchers did not observe accelerated aging in depression and aging, which they hypothesize may be due to different types of brain patterns for these disorders.

Large-scale, longitudinal studies of humans whose mothers smoked marijuana once or more per week and experimental work on rodents exposed to cannabinoids in utero have yielded remarkably consistent intellectual and behavioral correlates of fetal exposure to this drug. Some exposed individuals exhibit deficits in memory, cognition, and measures of sociability. These aberrations appear during infancy and persist through adulthood and are tied to changes in the expression of multiple gene families, as well as more global measures of brain responsiveness and plasticity. Researchers currently consider these perturbations to be mediated by changes to the endocannabinoid system caused by the active compounds in cannabis. 

The importance of the published findings and the emerging research regarding the potential negative effects of marijuana on brain development are a cause for concern despite the limited research and are the basis for the following recommendations:

1. Women who are considering becoming pregnant or who are of reproductive age need to be informed about the lack of definitive research and counseled about the current concerns regarding potential adverse effects of THC use on the woman and on fetal, infant, and child development. Marijuana can be included as part of a discussion about the use of tobacco, alcohol, and other drugs and medications during pregnancy.
2. As part of routine anticipatory guidance and in addition to contraception counseling, it is important to advise all adolescents and young women that if they become pregnant, marijuana should not be used during pregnancy.
3. Pregnant women who are using marijuana or other cannabinoid-containing products to treat a medical condition or to treat nausea and vomiting during pregnancy should be counseled about the lack of safety data and the possible adverse effects of THC in these products on the developing fetus and referred to their health care provider for alternative treatments that have better pregnancy-specific safety data.
4. Women of reproductive age who are pregnant or planning to become pregnant and are identified through universal screening as using marijuana should be counseled and, as clinically indicated, receive brief intervention and be referred to treatment.
5. Although marijuana is legal in some states, pregnant women who use marijuana can be subject to child welfare investigations if they have a positive marijuana screen result. Health care providers should emphasize that the purpose of screening is to allow treatment of the woman’s substance use, not to punish or prosecute her.
6. Present data are insufficient to assess the effects of exposure of infants to maternal marijuana use during breastfeeding. As a result, maternal marijuana use while breastfeeding is discouraged. Because the potential risks of infant exposure to marijuana metabolites are unknown, women should be informed of the potential risk of exposure during lactation and encouraged to abstain from using any marijuana products while breastfeeding.
7. Pregnant or breastfeeding women should be cautioned about infant exposure to smoke from marijuana in the environment, given emerging data on the effects of passive marijuana smoke.
8. Women who have become abstinent from previous marijuana use should be encouraged to remain abstinent while pregnant and breastfeeding.
9. Further research regarding the use of and effects of marijuana during pregnancy and breastfeeding is needed.
10. Pediatricians are urged to work with their state and/or local health departments if legalization of marijuana is being considered or has occurred in their state to help with constructive, nonpunitive policy and education for families.

They also discovered that prenatal marijuana use was associated with a 50 percent increased chance of low birth weight regardless of tobacco use during pregnancy. “Growing evidence suggests prenatal cannabis exposure has a detrimental impact on offspring brain function starting in the toddler years, specifically issues related to attention deficit disorder,” Crume said. “But much of the research on the effects of prenatal cannabis on neonatal outcomes was based on marijuana exposures in the 1980s and 1990s which may not reflect the potency of today’s cannabis or the many ways it is used.”

Even after less than six years of smoking the drug, the ill effects were already being seen on their breathing, according the research presented at the British Thoracic Society (BTS) winter meeting.
 
"It is vital that young people understand the dangers of both cigarette and cannabis smoking since these habits can start having a serious impact on their lungs at an early stage."
 
 

Everyone should be concerned:  Voters, not medical practitioners or scientists, have been able to determine medical practice.
Beneath it all, however, we must pause to seriously consider the known, detrimental effects of repeated marijuana use on the developing adolescent brain.  We must act accordingly and responsibly in ways that promote the public health and safety, help delay initiation of use, and reduce, not increase, the accessibility of marijuana to this particularly vulnerable population.

Here are just a few of the health effects you may want to know:

• Marijuana use directly affects the brain—specifically the parts of the brain responsible for memory, learning, and attention.
• The compounds in marijuana can affect the circulatory system and may increase the risk of heart attacks and strokes.
• Smoking marijuana can lead to a greater risk of bronchitis, cough, and phlegm production.
• Marijuana users are significantly more likely than nonusers to develop chronic mental disorders, including schizophrenia. Schizophrenia is a type of mental illness where people might see or hear things that aren't really there (hallucinations).
• Eating foods or drinking beverages that contain marijuana have some different risks than smoking marijuana, including a greater risk of poisoning.
• About 1 in 10 marijuana users will become addicted. For people who begin using before the age of 18, that number rises to 1 in 6.
• Some research shows that using marijuana while you are pregnant[288 KB] can cause health problems in newborns—including low birth weight and developmental problems.
• Marijuana use can slow your reaction time and ability to make decisions when driving[271 KB].

“We see specific morphological changes in the brain to important neurotransmitter systems, and individuals who are exposed to THC early in life show greater sensitivity to opiates than others do,” she said. “We know that the brain definitely adapts to marijuana. It is profoundly changing the receptors and receptor signaling that impact gene expression. And the changes it makes last through adulthood and even into the next generation. So we see that there’s something about the ongoing processes in the developing brain that this drug somehow sensitizes—in the cells, the receptors, and in the signaling cascades—that makes kids more vulnerable to addiction and other problems later.”

“There is a lot of optimism for what components of the marijuana plant may offer on a medicinal level but, like all other drugs, the caveat is that you have to know what it does, what population it can be used for, and who could be vulnerable to its effects. We need a lot more research before we can say anything concrete about its future as a treatment.”

Connection between legalization of marijuana and increase opioid addiction.
The effects of marijuana on the brain of an unborn child. Predisposing children for addiction. Here are the studies cited. 

KNOW YOUR A,B,C,D’s   …  Absent, Behavior, Course Grade = Drugs
 

Summary: Cannabis use during pregnancy is associated with abnormal brain structure in children, according to a new study. Compared with unexposed children, those who were prenatally exposed to cannabis had a thicker prefrontal cortex, a region of the brain involved in complex cognition, decision-making, and working memory.

“This is not a war on drugs , it is a defense of our brains!” Dr. Bertha Madras, PhD

"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.

 But at a bare minimum, these findings suggest we should be avoiding recreational cannabis use during pregnancy. 

Given these statistics.... is legalization worth the consequences....
Cannabis has been found to be the most frequently used drug in the U.S. after alcohol, tobacco and caffeine. 
The risk of developing addiction associated with cannabis use has been reported to increase to about 17% among those who start using marijuana in adolescence, and to 25-50% among those who smoke marijuana daily.
The long-term effects of marijuana use include altered brain development and cognitive impairment, including impaired neural connectivity in specific brain regions, decreased activity in prefrontal regions, and reduced volumes in the hippocampus.
Cannabis is most commonly consumed through smoking, a route of drug delivery that predictably has a variety of negative effects on pulmonary function. Smoke from marijuana combustion has been shown to contain a number of carcinogens and cocarcinogens, as well as many of the toxins, irritants, and carcinogens as tobacco smoke.  Additionally, marijuana smokers tend to inhale more deeply and hold their breath longer than cigarette smokers, which leads to a greater exposure per breath to “tar” (the carcinogenic solids in smoke). Regular smoking of marijuana, in the absence of tobacco, produces visible and microscopic injury to the large airways
http://www.asam.org/docs/default-source/publicy-policy-statements/mariju...

In 2014, Gilman published research on 18-to-25-year-olds that showed differences in the brain’s reward system between users and nonusers. Teens who smoked marijuana had significant abnormalities in the areas of the brain linked to emotion, motivation, and decision-making (see diagram above). “I got a lot of hate mail after that,” she says.