Joel’s medical condition in the HBO show is actually canon thanks to The Last of Us Part 1 Remake

gamesradar.com:

Joel's medical condition in episode 6 of The Last of Us HBO TV show does have some grounding in game canon – even though it might not feel like it. 

Warning! This article contains minor spoilers for The Last of Us episode 6 .

In episode six of the HBO show, Joel shows clear signs that he's having a panic attack in two separate scenes. They seem to be associated with his growing relationship and care for Ellie, as he explains later to his brother Tommy after their reunion. 

Now, these panic attacks are not something that are explored in the game at all, so fans of the series like myself will no doubt have scratched their heads a little at the deviate from the source material. However, it turns out there is a history of Joel having anxiety issues when you take a look at the recently released The Last of Us Part 1 Remake. 

Right in the opening hour, you take control of Sarah as she looks for her dad just as the outbreak starts. She's looking round the house for any sign of him, and if you take a detour into Joel's bedroom you can go into Photo Mode and zoom in on the bedside cabinet. 

It's here you'll see a little pill bottle that you can see above reads "anti-anxiety medication tablets" – a little clunky sounding, sure, but clearly an indication that the HBO Show isn't taking Joel's panic attacks completely out of nowhere. 

Elsewhere in Episode 6 we also get a flash of who we assume is Dina – a character who plays a pivotal role in Ellie's life in The Last of Us Part 2. Plus, there's also an early introduction to Shimmer, who becomes Ellie's horse companion also in The Last of Us Part 2 (sob). 

Check what other big changes episode 6 has between The Last of Us TV show and game