Noted

Alex Eben Meyer

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Since the 1960s, scientists have known that a cascade of climatological events could create a “snowball Earth”: a planet entirely covered in ice. The Earth entered lengthy “snowball” states at least twice during the Neoproterozoic era (720 to 635 million years ago).

Explanations for what precipitated these global glaciation periods have been inconclusive, but recent findings by a Yale-led research team support the idea of an asteroid strike as the culprit. The study was published in Science Advances.

Using computer models based on a known asteroid strike from 66 million years ago, researchers simulated its impact under various conditions. They determined that if a similar strike occurred during the frigid Neoproterozoic era, it could have triggered the snowball effect by ejecting material into Earth’s atmosphere sufficient to block out the sun’s rays—thus tipping Earth’s system into runaway cooling.

Analyzing data from the 2019–20 National Health and Resilience in Veterans Study, a Yale-led team found that 7.9 percent of veterans screened positive for probable generalized anxiety disorder (GAD), in line with 7.6 percent of US adults overall. GAD is characterized by persistent and excessive anxiety that can disrupt everyday functioning. Researchers also estimated that almost one in four veterans likely experience mild anxiety disorders.

Vets with probable GAD had higher rates of past-year suicidal ideation and lifetime suicidal attempts, compared with groups that had mild anxiety or no GAD. But even mild anxiety symptoms are associated with elevated rates of co-occurring psychiatric and functional difficulties, as well as suicidal thoughts and behaviors. Researchers suggest that brief screening measures to assess both mild and severe anxiety symptoms could increase veterans’ access to care.