When a beloved TV series comes to a finish, it’s common to hear fans say they’re “grieving” the ending of a story they’ve watched and kept up with, sometimes for years. But what is the reasoning behind these intense, and often immediate, emotions?

Litsa Williams is a clinical social worker and one of the founders of What’s Your Grief?, an online community focused on grief education and expression. She noted that there are varying degrees of grief (as in, the conclusion of a movie or show is obviously not the same as the death of a person), but many people do experience feelings of loss around different forms of media, such as the ending of a favourite show.

“It certainly is a loss that we’re experiencing,” she said. “It’s a natural reaction we’re going to have.”

HuffPost reached out to more mental health professionals to better understand why exactly TV shows can cause such a strong sense of sadness when they end.

You connect to the stories and characters

The most obvious reason is that you’ve built a connection to the storyline and the characters.

“Even when it’s fantasy, there’s a genuine investment in the outcome of a story and the state of the various characters,” said Brian Kong, PsyD, a Chicago-based psychologist who often explores the intersection of therapy and pop culture.

These connections to fictional stories and characters are why many people share their opinions about the plots and characters’ actions. The connection can be especially strong for long-running series and beloved (sometimes nostalgia-inducing) characters.

As examples, Kong referenced Episode 5 of the final season of “Game of Thrones” (and a certain decision made by main character Daenerys Targaryen), which many viewers did not like, as well as the “Sonic the Hedgehog” movie trailer, which prompted many fans of the video game character to voice their concerns over the hedgehog’s appearance.

“People feel so connected, and in some cases, like they have ownership over something, whether it’s, ‘Sonic isn’t supposed to look like that’ or ‘This is completely inconsistent to how Daenerys’ character has been developing,’” he said. “There’s a real, strong reaction to that.”

Kong added that viewers have a right to share their opinions, both positive and negative, about the media they’re consuming. The feedback simply proves how some TV series can connect with viewers so well.

He said that these connections can also be seen with celebrities and sports teams: “It’s similar to a football fan expressing outrage over a play or trade that they disagree with.”

The show is a form of temporarily checking out

Kristen Diou and Anna Zapata are the licensed professional counsellors behind “Pop Culture Therapists,” a podcast that explores how movies and shows depict mental health topics and conditions. They said that for many people, watching a show regularly can be a form of temporarily checking out of what’s going on in the real world.

“It’s a way we detach from our own issues, our own problems,” Diou said. “We can be more mindless. The thought of giving that up and coming back to our own world is a little frightening for people.”

A TV show can also be something to look forward to every week, and with its ending comes one less thing to anticipate.

“Depending on what else is going on in your life, that can be something really important,” Williams said.

Williams noted that it’s “totally normal to feel a deep sense of loss to something that we value,” but if shows or other forms of media are taking the place of regular relationships, then it’s time to reevaluate their role in your everyday life.

The length of the series is a way of looking back on your life

For a series like “Game of Thrones,” which has been on since 2011 and famously made fans wait several months for new episodes, the series can feel like a large part of viewers’ lives.

“‘Game of Thrones’ is a really long-running show,” Williams said. “It causes us to reflect on how our life has evolved for how long the show has been on.”

Kong agreed that in a span of eight years (the length of “Game of Thrones”), seven years (the length of “Veep”) or even only five years (the length of “Breaking Bad”), people can experience many life changes. Having a constant like a TV show is often a way to reflect on what’s happened over the years.

“It reminds us of the passage of time and where we were and who we watched it with,” he said.

You’re going to miss the experience of watching (and talking about) it

The actual experience of watching the show ”• whether it involves the same group of people, centres around a certain meal, or focuses on another viewing party tradition ”• can also add to those feelings of loss once the series ends.

“It becomes a ritual for people,” Zapata said. “It’s a loss not to have our favourite Sunday night ritual.”

Kong said that the post-episode conversation, especially for a show that becomes a “social phenomenon” like “Game of Thrones,” can also serve as something to be missed.

“It’s a shared collective experience, like the Super Bowl or the moon landing,” he said. “We watch it in groups, and even if we don’t, we still theorize and speculate together.”

While it’s normal to feel emotional over the ending of a long-running series, if viewers are having a deeper sense of loss, it’s important to acknowledge what function the show served in the viewer’s life.

If it served as a social component, viewers can connect with friends to come up with another weekly ritual or watch another show to be a part of its community. If the series played a larger role and the post-episode emotions are a sign of something more serious, it might be time to talk to someone.

“It could be an indication you should reach out to other people,” Kong said.