Deaths from opioid overdoses have increased by 87% since 2009, national data shows. Medics say that the epidemic has reached a "new level of crisis".
A study of nearly 4 million intensive care unit patients in 162 hospitals in 44 states has found that about 22,000 patients were admitted for opioid overdoses between the start of 2009 and the end of 2015.
Patients admitted for an overdose required increasingly intensive care, according to the study, which is published in the Annals of the American Thoracic Society.
Overall, admissions for overdoses increased by almost half, from 45 patients per 10,000 to 65 per 10,000. Average mortality among those who overdose rose steadily by about 0.5% every month through the study period – meaning that people admitted were increasingly likely to die due to the severity of their condition.
Throughout the first years of data studied, the increase in overdose deaths rose steadily, but then that quickly changed.
"The real uptick came after 2012. The study from 2009 to 2015, but it's really quite a J-shaped curve," Jennifer Stevens of the Beth Israel Deaconess Medical Centre and Harvard Medical School told IBTimes UK.
The study was based on billing data from the hospitals, showing how much it was costing to treat overdose patients. This limited the detail the researchers could go into about the nature of these patients' illness.
In a large-scale study such as this, the researchers expected mortality to decrease over time, as hospitals become more proficient at quickly and effectively treating patients.
"The fact we saw mortality going up ran against our initial hypothesis and was really quite troubling," said Stevens.
"This is just a marker of exactly how severely ill this patient population has become."
The findings come in the same week that a study has found that 1 in 8 Americans have received a clinical diagnosis of alcoholism. Previous studies have also found that heroin use in the US is at an all-time high, increasing five-fold in just one decade.