A study published in the journal Pharmacoepidemiology & Drug Safety (PDS) examined trends in prescription opioid use in the United States from 1999 through 2000, and from 2013 through 2014, and results were compared. Specifically, this study looked at long-term opioid use, which was defined as the use of prescription opioids for 90 days or longer. In 1999-2000, 4.1% of adults were taking prescription opioid medications, and from 2013 through 2014, 6.8% of US adults were taking prescription opioids. The increase was mostly driven by an increase in the long-term use of prescription opioids, which increased from 1.8% of adults to 5.4%. Long-term use of opioids correlates with many negative health consequences. Long-term use of opioids is associated with worse physical health, a higher incidence of benzodiazepine use, and higher rates of heroin addiction. Therefore, the study concludes, it is essential that doctors carefully weigh the risks and benefits of long-term opioid use in their patients before prescribing it. A CDC study from 2017 reported that the sharpest increase in the likelihood of long-term dependency on prescription opioids came just five days after the initial prescription. Another spike in dependency was seen after one month. In general, however, the longer a prescription, the greater the risk of long-term addiction. Long-term opioid use was also associated with other types of addictions. For example, the study published in PDS found a higher risk of alcohol abuse and heroin abuse among people who had been prescribed opioids for long periods. A 2016 study published in Addiction Science & Clinical Practice reported that alcohol misuse among people in medication-assisted addiction treatment for opioid use disorder was common and was associated with a greater risk of death.