‘This Is Us’: Chris Sullivan Teases Toby's 'Backstory' of Secret Struggle (Exclusive)

The NBC hit will dive deeper into Toby's history with depression on Tuesday's episode.

This Is Us fans are in for a ride with Tuesday's episode. 

The NBC hit will dive deeper into Toby's backstory this week, as his struggle with depression comes center stage. 

"If you're going off your medication without consulting a doctor, it's probably not a good idea," Chris Sullivan teased of his character's arc this season, to ET at the show's premiere last month, noting that exposing Toby's dark secret made for a "beautiful" episode. 

"It's nice to see Toby's backstory, [to] see a little bit of history [and] figure out why he's developed into the person he is today," he continued. "I think that will only bond the audience to him."

According to Chrissy Metz, Toby's mental health struggles could have enormous effects on his relationship with her character, Kate. Fans saw earlier this season that Toby was willing to do anything to give Kate the baby she so desperately wants -- including, secretly flushing his antidepressants down the toilet. 

"You see that Toby is continuing to sacrifice for his relationship, and for the love of Kate, which is so beautiful but could be very detrimental to himself," she noted while speaking with ET earlier this month. 

Also struggling a bit this season is Sterling K. Brown's Randall, who is trying to run for office. For the actor, however, it's the tough times that have had a big impact on him as a person. "The heart of the man is so pure," he recently told ET. "Like, playing Randall makes me a better person." 

This Is Us airs Tuesdays at 9 p.m. ET/PT on NBC. See more on the show in the video below.