This week on r/science, the community coalesced around a throughline: clear public-health wins coexist with new, behavior-linked risks, while social strains among younger generations intensify against a backdrop of polarization. At the same time, fresh evidence continues to overturn comfortable assumptions—from the neurobiology of aging to the peopling of the Americas.
Public health: clear wins, evolving risks
Decades of policy are paying dividends. A century-spanning hair analysis confirms that phasing out leaded gasoline and paint dramatically curtailed human exposure, a signal success story in protecting brain development. In parallel, prevention is still the biggest lever: a massive global study estimates more than one-third of cancers are attributable to modifiable risks, led by tobacco and alcohol—underscoring the gap between evidence and public awareness on alcohol’s role.
"What an incredible success story, even though it also involved a lot of politics and avoidable suffering." - u/ThoughtsandThinkers (2285 points)
The week also surfaced less obvious externalities and emerging mechanisms. Danish registry evidence suggests a “crime externality” following diagnosis, with a 14% rise in offending after cancer that robust safety nets appear to blunt—reframing healthcare support as public safety. And biomedical frontiers are shifting: researchers linked a common eye bacterium to neurodegeneration, as Chlamydia pneumoniae was found in the retina and brain alongside inflammatory pathways tied to Alzheimer’s, hinting at infectious triggers and retinal imaging as a noninvasive screen.
"All I get from these studies is that inflammation is the real killer." - u/FenderFan05 (1637 points)
Generational wellbeing under pressure
Indicators of distress are migrating younger. Drawing on more than half a million responses, data spanning 15 years show a marked rise in depression symptoms among U.S. college students—steepest after 2016 and especially for women, racial minorities, and those under financial strain. Even in high-happiness nations, the cohort split is stark: a Swedish national survey finds young adults lonelier, more anxious, and less financially secure than older groups, despite older Swedes’ thriving skewing national averages upward.
"Something else happened in 2008 that a lot of people with a certain ideology REALLY didn’t like and caused a huge rift between political ideologies … I juuuust can’t put my finger on it though." - u/K1ngofnoth1ng (6938 points)
Macro- and micro-dynamics meet here: polarization is not an abstraction when a long-term analysis charts a 64% rise in U.S. political and social polarization since 1988, with most of the increase concentrated after 2008. Even everyday social scripts reflect shifting norms, as research on post-date texting suggests the “next morning” message best balances interest with autonomy, illustrating how small behavioral cues can either buffer or amplify ambient uncertainty.
Evidence that unsettles assumptions
Two threads challenged popular priors. In neuroaging, a study of adults aged 40–77 associated cannabis use with larger brain volumes and better cognitive performance, with caveats about product composition and causality—an invitation to refine, not finalize, our models of dose, age, and modality.
"Clovis who? It really is a shame that so many good scientists were blackballed in the late 90’s/early 2000’s for even HINTING at human habitation prior to Clovis." - u/Hipcatjack (217 points)
And in deep time, archaeology delivered a jolt: 14,000-year-old mammoth ivory tools in Alaska push credible human activity north of Clovis, strengthening a Beringia-to-interior migration arc while leaving room for even earlier arrivals. The throughline matches the week’s mood: let the data revise the story, whether the subject is brains, behaviors, or beginnings.