Grist: Killing weeds with toxic chemicals might be making farmers clinically sad. A study of more than 700 French farmers and farmworkers found that those who used herbicides were more likely to be treated for depression than were those who avoided the stuff. From Reuters: [W]hen the researchers took into account factors linked with depression, such as age and cigarette smoking, they determined that those farmers exposed to weedkillers were nearly two and a half times as likely to have had depression....