It's in the Genes. And the Milk. 

If you're breastfeeding, you shouldn't be using marijuana.

While that's long been the stance of the American Academy of Pediatrics, it's now supported by science. Researchers at the University of California San Diego School of Medicine released a groundbreaking study this month showing that cannabinoids — the active compounds, including THC, found in cannabis — can pass through a mother's body and into her breast milk for up to six days after her last reported use.

The study tested breast milk samples from 54 women who reported using marijuana either daily, weekly or sporadically, and found that 63 percent of the samples tested positive for THC and other cannabinoids, which bound to the fat molecules in the milk. While the research makes clear that these cannabinoids would then pass into the system of a breastfeeding child, it does not quantify the potential impacts, saying only that the data raises neurodevelopmental concerns.

"We found that the amount of THC that the infant could potentially ingest from breast milk was relatively low but we still don't know enough about the drug to say whether or not there is a concern for the infant at any dose, or if there is a safe dosing level," explained Christina Chambers, the study's principal investigator and a professor in the department of Pediatrics at UCSD School of Medicine, in a press release.

While the benefits of breastfeeding are now widely accepted — it's associated with reduced risks of obesity, asthma and sudden infant death syndrome, to name a few — this study now gives pediatricians something to point to when breastfeeding mothers ask about the safety of using marijuana.

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Another groundbreaking study released this week provides further evidence of an undeniable link between cannabis use and schizophrenia, though it stops well short of establishing a causal connection.

Published in Nature Neuroscience, the study saw geneticists analyze DNA samples from more than 180,000 people — the largest grouping to date for a study of this kind — and found that people who are genetically at risk of schizophrenia are more likely to start using cannabis.

Using a variety of tests, the geneticists found 35 different genes associated with cannabis use, with many of them already associated with other habits, personality traits and mental health conditions, including schizophrenia.

"That was not a big surprise, because previous studies have often shown that cannabis use and schizophrenia are associated with each other," the study's lead author, Jacqueline Vink, a researcher at Radboud University in the Netherlands, said in a statement. "However, we also studied whether this association is causal."

The researchers reported finding some evidence that being genetically vulnerable to schizophrenia made people more likely to use cannabis, potentially as a way to self-medicate and cope with their condition. Other studies have found that cannabis use early in life increases one's risk of schizophrenia, and Vink and her crew were careful to say their study doesn't disprove this theory but rather shows the relationship is complicated and warrants further study.

Interestingly, the geneticists also used their research to calculate that genetic variations alone may account for 11 percent of the differences in people that determine whether they smoke cannabis.

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With the 2017-2018 legislative session coming to a close Aug. 31, there has been a flurry of activity in Sacramento as lawmakers push to get their bills on Gov. Jerry Brown's desk before they are relegated to the dust bins of history. Amid the whirlwind of activity, a number of cannabis-related bills have been passed in recent days.

The state Senate passed Assembly Bill 1793, which would require the Department of Justice to comb through its database for cannabis convictions in cases from 1975 to 2016 for conduct that would now be deemed legal under Proposition 64 to systematically expunge records and reduce sentences. If the bill is signed by Brown, the state's district attorneys would have one year to challenge any retroactive action proposed by the Department of Justice. It is estimated the law would require the review of more than 215,000 convictions.

On Aug. 27, the state Assembly passed North Coast Sen. Mike McGuire's bill that would expand the statute of limitations for illegal conversions of timberlands for cannabis cultivation to three years from the time of their discovery, which McGuire argues will enable more prosecutions. The bill is supported by a host of environmental groups, as well as the California District Attorneys Association.

Also on Aug. 27, the Legislature passed a bill that would require the California Highway Patrol to track and report how many motorists pulled over on suspicion of impaired driving are allegedly under the influence of marijuana. The bill is intended to quantify the impacts of cannabis legalization on California roadways.

Finally, the Assembly passed another bill Aug. 27 that would allow some parents to give their children medical marijuana on school campuses. The legislation — which allows local districts to opt out — would allow minors with medical marijuana prescriptions to take the medication on campus, so long as it comes in a non-smoking or vaping form, such as capsules or oils.

Thadeus Greenson is the Journal's news editor. Reach him at 442-1400, extension 321, or [email protected]. Follow him on Twitter @thadeusgreenson.