Marijuana legalization in many U.S. states is having a predictable effect: Many people now consume THC and CBD products recreationally and for health and well-being – to help with sleep, anxiety or nausea, for instance. But commercialization was done with relatively little understanding of the health effects of cannabis.

Wayne State University neuroscientist Hilary Marusak surveys the mounting research showing the damage THC and CBD can cause during periods of rapid development, including on pregnant women and teens. “People often assume there’s no risk when using cannabis or cannabinoids during vulnerable periods of life, but they’re basing that on little to no data,” she writes.

Recent headlines about the bird flu, which has now infected mammals, are not reassuring, particularly with spring migration coming. A group of University of Colorado Boulder virologists explains why scientists are closely watching the spread of H5N1, which has led to the destruction of millions of commercially raised birds and is harming wild birds and other animals. Their article also details what it would take at the molecular level to spread to humans.

The biggest news related to science this week was the release of the U.N.’s latest assessment report on climate change – this article recaps the key points while this one explains why embracing speed and innovation is critical to making progress on climate. Another big environmental story over the past week was the release of proposed federal regulations for so-called forever chemicals known as PFAS. A water quality scientist writes that there’s a strong need for limits, but complying will be expensive and likely face legal challenges.

Also this week science news:

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Marijuana use by the mother can affect a baby’s brain development. John Fedele/Tetraimages via Getty Images

Mounting research points to health harms from cannabis, THC and CBD use during pregnancy, adolescence and other periods of rapid development

Hilary A. Marusak, Wayne State University

Studies show that smoking marijuana during pregnancy can lead to premature birth, lower birth weight and psychological problems in the newborn.

Bird flu is transmitted mainly by wild birds, like these snow geese in Ruthsberg, Md., in January 2023. Photo by JIM WATSON/AFP via Getty Images

As bird flu continues to spread in the US and worldwide, what’s the risk that it could start a human pandemic? 4 questions answered

Sara Sawyer, University of Colorado Boulder; Emma Worden-Sapper, University of Colorado Boulder; Sharon Wu, University of Colorado Boulder

Avian influenza viruses have evolved to infect birds, but the current H5N1 outbreak is also infecting a wide range of mammals. This suggests that it could mutate into forms that threaten humans.

Wildfires are becoming a greater risk in many countries as the landscape dries. Michael Nigro/Pacific Press/LightRocket via Getty Images

Climate damage is worsening faster than expected, but there’s still reason for optimism – 4 essential reads on the IPCC report

Stacy Morford, The Conversation

The final report in the IPCC’s sixth assessment series says countries will have to cut their greenhouse gas emissions 60% in the next 12 years to keep global warming in check.

Voice deepfakes are calling – here’s what they are and how to avoid getting scammed

Matthew Wright, Rochester Institute of Technology; Christopher Schwartz, Rochester Institute of Technology

Powerful AI tools available to anyone with an internet connection make it easy to impersonate someone’s voice, increasing the threat of phone scams.

Water in space – a ‘Goldilocks’ star reveals previously hidden step in how water gets to planets like Earth

John Tobin, National Radio Astronomy Observatory

Astronomers have long known where water is first formed in the universe and how it ends up on planets, asteroids and comets. A recent discovery has finally answered what happens in between.

3 reasons the Willow Arctic oil drilling project was approved – it’s the latest battle in a long fight over Alaska’s North Slope

Scott L. Montgomery, University of Washington

Biden vowed ‘no more drilling on federal lands,’ but Russia’s war on Ukraine and pressures at home are hard to ignore.

A friend who’s more boss than BFF may be harmful for teens’ mental health

Hannah L. Schacter, Wayne State University; Adam Hoffman, Cornell University; Alexandra Ehrhardt, Wayne State University

Friendships are important, but are they always healthy? New research finds that teens who feel dominated by their friends experience lower self-esteem and more symptoms of anxiety and depression.

Those seeds clinging to your hiking socks may be from invasive plants – here’s how to avoid spreading them to new locations

Megan Dolman, Boise State University

Invasive species cause billions of dollars in damage across the US every year. Hikers and backpackers can take simple steps to avoid spreading seeds and making the problem worse.

Why does time change when traveling close to the speed of light? A physicist explains

Michael Lam, Rochester Institute of Technology

Your experience of time is relative because it depends on motion – more specifically, your speed and acceleration.