The actor, who played Sabrina Spellman's love interest Harvey Kinkle on the Nineties show, discussed the conditions on Twitter. He quoted a message message from a fan who said they loved Richert growing up and wondered why he didn't appear in more works in the following years.
"Anxiety and subsequent depression were my major game stoppers," Richert, now 40, said.
"Took a decade to learn how to cope and overcome.
"Back then, all I knew was something was wrong with me, that I was broken and unworthy; all that fantastic BS anxiety likes to ruin your life with. But it didn’t."
Richert was a regular cast member in the first four seasons of the sitcom, before making a few appearances in season five.
He returned as a regular for the sixth and seventh seasons, until the show's finale in 2003.
His character has been reinvented in Chilling Adventures of Sabrina, Netflix's reboot of the Archie Comics franchise, in which Kinkle is played by Ross Lynch.
Richert, a native of St Paul, Minnesota, played in the short film H-e-n-r-y in 2006.
He appeared in the movie Gamebox 10 in 2004, as well as in the drama The Sure Hand of God.
In September this year, the actor explained on Twitter that he has held a number of day jobs in addition to his acting career.
"I’m currently a maintenance man, a janitor, a carpenter, and do whatever random jobs I can get to pay the bill," he wrote.
Richert said he has been "extremely lucky to have had any success at all", adding: "Actors so very rarely have job security or consistent work, quality healthcare, a reasonable retirement.
"We are actors anyway because it is who we are at the core, for the love and need to bring the words on the page to life and to make you feel them (God, I love to make you laugh!)"
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