This story was co-published with The New York Times.

This much is clear: The public is angry about the skyrocketing cost of prescription drugs. Surveys have shown that high drug prices rank near the top of consumers’ health care concerns.

What’s not as clear is exactly why prices have been rising, and who is to blame.

For the last four months, The New York Times and ProPublica, the nonprofit investigative journalism organization, have teamed up to answer these questions, and to shed light on the games that are being played to keep prices high, often without consumers’ knowledge or consent. Katie reports from the health desk at The Times, and Charles is a senior reporter at ProPublica.

Our reporting journey has turned up some counterintuitive stories, like how insurance companies sometimes require patients to take brand-name drugs — and refuse to cover generic alternatives — even when that means patients have to pay more out of pocket.

Along the way, we’ve asked readers to share their stories about their struggles with high drug costs. We’ve heard from nearly 1,000 people.

In recent weeks, a few stories caught our eye. A woman in Texas, for example, told us that the company that manages her drug benefits, OptumRx, was going to start asking her to pay more out of pocket for Butrans, a painkilling patch that contains the drug buprenorphine. As a “lower cost alternative,” OptumRx, which is owned by UnitedHealth Group, suggested she try painkillers like OxyContin, even though they carry a higher risk of dependence.

A letter sent by OptumRx, a pharmacy benefit manager, to a member in Texas, suggesting she consider switching from the Butrans painkilling skin patch to drugs that carry a higher risk of abuse and dependence. (Letter obtained by ProPublica)

“The whole point of pain management is to take the least amount of medication possible to manage your pain, so that you always have somewhere to go when the pain increases or changes,” she wrote to us. “This is irresponsible and scary ‘cost management.’” She did not want to use her name, saying her employer prohibited her from identifying herself, but she allowed us to share OptumRx’s redacted letter.

Her pharmacy benefit manager, she wrote, is “effectively contributing to the ‘opioid crisis’ with its own policies.”

A spokesman for UnitedHealth, Matthew N. Wiggin, said it takes the crisis seriously and wants to ensure that people with chronic pain get the appropriate treatment.

We’ve closely followed the opioid crisis and efforts to hold various parties accountable, among them drug manufacturers, pharmacies and emergency room doctors.

But these stories — about patients who believed their insurers were placing roadblocks in the way of less risky painkillers — felt new to us.

We followed up with several of the readers, and searched social media to see if other patients were talking about this.

Amid Opioid Crisis, Insurers Restrict Pricey, Less Addictive Painkillers Drug companies and doctors have been accused of fueling the opioid crisis, but some question whether insurers have played a role, too.

Then we asked for documents: billing statements from insurers, denial letters, call logs and doctors’ records. In the case of our lead example, a woman named Alisa Erkes, she also agreed to sign a privacy waiver allowing her insurer, UnitedHealthcare, to comment on her case.

Charles enlisted ProPublica’s deputy data editor, Ryann Grochowski Jones, to analyze data from Medicare prescription drug plans. The results showed that insurers were indeed placing more barriers to drugs like Butrans and lidocaine patches than to cheaper generic opioids.

Insurers say that they are doing their part by placing limits on new prescriptions for addictive painkillers, and that they are also doing more to monitor doctors’ prescribing patterns and to catch abuse by patients. Several insurers said they had seen declines in monthly opioid prescriptions, a sign of progress.

But their behavior has infuriated many patients, who say they want to avoid taking opioids if possible. They argue that insurers are too focused on a drug’s cost, since many of the painkillers with a lower risk of addiction are more expensive.

Our project examining high drug costs is not over. We are already digging into other corners of the prescription drug world, hoping to shed light on more of the hidden forces that are keeping drug costs high. Stay tuned, as well, for more stories that were inspired by our readers.

Have you had trouble paying for prescription drugs? Tell us about it.