Doctors are more likely to prescribe opioid painkillers at the end of a full day of appointments, or if they are running late, a discovery that may help address the nation’s crisis with the addictive pills. A University of Minnesota researcher hopes her new finding will warn doctors that the stresses of hectic days can influence their prescribing judgment.

“You can imagine that when physicians are under more time pressures, later in the day, or when they’re running behind schedule, their decisions might change,” said Hannah T. Neprash, a U public health researcher who led the study.

Neprash reviewed 678,319 U.S. clinic appointments in 2017 involving patients who hadn’t received opioids before. During the first three appointments of the day, doctors prescribed opioids to 4% of patients complaining of migraines or joint or back pains. By their 20th appointments, doctors prescribed opioids to 5.6% of patients, a 33% jump.

Similarly, opioid prescribing rose by 17% when appointments were an hour or more late.

Results of the study, published in the JAMA Network Open online medical journal, did not address why doctors’ prescribing changed. One theory is that sicker patients come to clinics later in the day, but the study didn’t find a comparable increase over time in the amount or dosage of opioids prescribed.

Another theory is that doctors try to make up for lost time, whether they realize it or not, by forgoing labored conversations with patients about trying alternatives to opioids first. “It takes cognitive effort to push back against a patient who is demanding opioids if they’re not appropriate for that patient,” Neprash said. “It might take more to muster that ... effort when you’re rushed or it’s later in the day.”

The study also didn’t address whether the opioid prescriptions were appropriate., although the U.S. Centers for Disease Control and Prevention has determined that opioids should not be first-line therapies for chronic pain.

The study comes amid efforts to reign in a national epidemic of rising addictions and overdose deaths.

Neprash’s finding concurs with a smaller 2018 study by Mayo Clinic researchers that found that opioid prescriptions were more likely at appointments after 2 p.m.

Her finding was specific to opioids. Neprash found no increase in ordering of physical therapy or more common NSAID painkillers during afternoon appointments. “It’s consistent with the common narrative that opioids might be a quick fix,’’ she said.

Solutions include spreading out appointments or requiring documentation of shared-decisionmaking discussions that prevent doctors and patients from rushing into opioid prescriptions.