(CNN) Kyle Casey was an exceptional athlete, a star baseball player in high school. He had a contagious smile, dark hair and glimmering blue eyes. He stole the hearts of everyone around him -- all while developing a deadly drug addiction.

Last year, Kyle died from a drug overdose. He was 22.

As she reflects on his life, Lisa Sullivan, 56, said she didn't know how long her son Kyle was experimenting with drugs. But after he graduated from high school in Maine, she saw her healthy son spiral into a depressed and sickly young man. She felt helpless.

"In my son's instance, I really feel that he thought he was going through a phase. I don't think he looked at himself as a drug addict. I don't think he felt he was addicted to drugs," Sullivan said.

Over time, the money Kyle made from working up to 70 hours a week as a landscaper was swiftly disappearing, buying opioids at $40 per pill and eventually going toward heroin to snort.

"You try to figure out, being a parent, why was he taken from me? Why, why did this happen? But I really feel that God had a purpose for him and that it was for him to help others," Sullivan said. "Though he couldn't do it on Earth, he's doing it from heaven."

After Kyle died, his heart, liver, two kidneys and intestines were all donated to help people in need of organ transplants -- from a mother in her early 20s to a grandfather in his late 60s, Sullivan said. In her grief, Sullivan now finds solace in the fact that Kyle's tragic death changed lives.

"He helped five people. Not only the five people who got his organs but also all of their families," she said.

'A changing face of organ donation'

Sullivan, a single mother who raised Kyle and his older sister, Stacey, said that far too often, she is learning about young men and women who are dying of similar overdoses. She hopes Kyle's death can raise awareness and make a difference.

While heartbreaking, it turns out that the recent rise in drug overdose deaths -- especially those involving opioids and heroin -- across the country has resulted in an unexpected increase in organ donations.

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"The opioid epidemic is a tragedy that has had an unexpected lifesaving legacy in donation and transplantation," said Alexandra Glazier, president and CEO of the New England Organ Bank

"While this doesn't lessen the tragedy in any way, there is something meaningful happening in saving lives through donation and transplantation that's coming from these deaths. We have seen a changing face of organ donation over the past several years related to the drug epidemic."

Epidemiologists across the country point to heroin and synthetic opioids, such as fentanyl , as the main contributors to the increasing number of drug-related deaths in the United States

From 2001 to 2014, the country experienced a 3.4-fold increase in the total number of overdose deaths from prescription opioid pain relievers, according to the National Institute on Drug Abuse . During that same time period, there was a whopping sixfold increase in the total number of overdose deaths from heroin, the data showed.

"In the last few years, the number of deceased donors has increased fairly significantly, and looking at the reasons for that, the largest group accounting for that increase is in the drug overdose cause of death," said Dr. David Klassen, chief medical officer at the United Network for Organ Sharing

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About a decade ago, Klassen said, drug overdoses accounted for 3% of the donor population. That number is expected to rise to 12% this year.

"The fact that the need for transplantable organs is so great and that, statistically, 22 people die every day for lack of an organ has probably contributed to more transplant programs considering organs from individuals dying from drug intoxication," said Kent Holloway, CEO of Lifeline of Ohio , a nonprofit organization that promotes and coordinates the donation of organs and tissue for transplantation.

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Ohio is one of the five states with the highest rates of drug overdose deaths in 2014, according to the Centers for Disease Control and Prevention ; the other four are West Virginia, New Mexico, New Hampshire and Kentucky.

"When all of this is said and done, what this means to us is that donors, in advance of their passing, or their families made the decision to make something very good come out of a tragic situation," Holloway said. "These donors have saved lives. They have given complete strangers a second chance for a healthy future."

Kyle's choice to save lives

Sullivan remembers the day Kyle registered to be an organ donor. It was a cheery spring afternoon in Maine, she said. Kyle had just gotten a new truck and was getting his driver's license for the first time at 18 years old.

"I remember that day so well because he had waited to get his license, so he was really excited that the day had finally come," Sullivan said.

"When we finally did go to get his license, I mentioned organ donation to Kyle, and he didn't even have to think about it. It was an automatic yes. That's just how Kyle was," she said. "He had such a loving personality. He didn't want anyone to be sad. He wanted everyone to be happy, and that's why I know he's looking down on those people that he saved and smiling. I know he is."

When Kyle registered to be an organ donor, he joined about half of the nation's adult population. More than 130 million adults in the United States have registered as organ donors as of last month, according to the national Department of Health and Human Services.

"That's approximately 50% of the adult population, and we definitely see that reflected in this sub-population" of donors who have died of a drug overdose, Glazier said. "Many of these donors have registered their own decision to be a donor."

Sullivan said she told Kyle's doctors about his decision to be an organ donor on the day he died.

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Kyle was visiting some friends in Massachusetts last year when he overdosed, Sullivan said. It was a cold and snowy day in March, and he was admitted to Lahey Hospital and Medical Center in Burlington. A combination of drugs was found in his system.

When Kyle was brought to the hospital, he was immediately put on life support.

"Kyle was in the hospital for three days," Sullivan said. "When his doctor that was taking care of him stated that there's nothing we could do ... I did say that Kyle, by his own choosing, is an organ donor."

Within a minute or two, Sullivan said, she was placed on the phone with the New England Organ Bank, which facilitated Kyle's organ donation.

Organs after overdoses

Even though people are dying from drug overdoses, that doesn't necessarily affect whether their organs can be donated, experts said.

"Narcotics in and of themselves are not necessarily toxic to organs. You know, narcotics cause people to stop breathing and cause their heart to stop, and in those situations, people become brain-dead within a matter of minutes," said Klassen, of the United Network for Organ Sharing.

"But in fact, their organs are potentially very suitable for plantation, so kidney function, liver function, even heart and lung function can be quite good. People dying of drug overdoses also tend to be younger and healthier," he explained. "It turns out actually the organs that are donated by patients who die of overdoses really can be, from a transplant perspective, really good organs."

When an organ donor dies of a drug overdose, the nation's Public Health Service and CDC categorize them as an "increased risk" donor, Glazier said.

In other words, organs from the potential donor might be at an increased risk for certain infectious diseases -- and to determine such, the donor's family is typically interviewed about the donor's medical and social history and behaviors.

"But I think our understanding collectively in the field of organ donation and transplantation of how to view that risk has changed," Glazier said. The incidence of disease transmission in organ transplantation is estimated to be as low as 1%, according to a 2012 study in the journal Emerging Infectious Diseases.

"The risk of dying waiting for an organ is the biggest risk that many of these patients face and so in evaluating the potential increased risk that comes with an organ from a donor who died of an overdose, it needs to be in that context," she said. "In that context, the bigger risk is the risk of not getting a transplant, versus the potential for a disease transmission."

'His heart's beating in someone else'

Some of the people who received Kyle's organs were facing the risk of not receiving an organ at all -- and now they feel as if they have a new life, Sullivan said.

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The recipient of Kyle's left kidney hopes to connect with Sullivan and her family, she said. Sullivan added that she also wants to meet the 66-year-old grandfather who was the recipient of Kyle's heart.

"His heart's beating in someone else," Sullivan said of her son before falling into a deep sob.

"I'm sorry," she said with a sniffle. "Organ donation ... it just gives you a reason to keep going, to know that something good came out of something so tragic. ... What I'm looking forward to right now is one day hearing Kyle's heart beat again."