More than 47,000 Americans died by suicide in 2017, twice as many as by homicide, according to the latest federal count, and another 1.4 million attempted to take their lives. The nation's suicide rate has been rising since 2000 among nearly every age group, particularly adolescents, young adults and middle-aged men. Researchers cite a variety of theories for the increase, including undiagnosed or untreated mental health problems, fallout from the opioid crisis, economic pressures, easy access to guns and increased use of social media by the young. New drug and psychological therapies offer some hope of effective treatment for those at risk of suicide, but experts say health care providers, suicide counselors, family members and others need better ways to spot signs of suicide risk. Some researchers are looking to artificial intelligence and machine learning as potential tools. Meanwhile, a new treatment based on the old party drug ketamine is being tested as a rapid-acting treatment for severe depression.