The This Is 40 star joined Twitter on January 3 shortly after being the subject of an online death hoax, joking at the time: "I'm incredibly late to the party but I'm here nonetheless, so what now?"
She closed the account several days later and announced on Facebook that she likely will never be a major proponent of social media.
Fox spoke to Access Hollywood at the Golden Globes on Sunday (January 13) about quitting Twitter, citing her newborn son as the motivating factor in her decision to take time away from social media.
"I gave in to see what it was all about - I don't have the time to keep up with Twitter," she explained.
"I have a baby that I need to take care of and I don't ever want my son to look at me and ask why I'm always on the computer or always on the phone and my answer to be that I'm 'social networking'. So, he's my priority and it's just not for me."
Fox added: "Some of the fans made me laugh a lot - some of them are really funny - and I'll miss interacting with them."
The actress and husband Brian Austin Green welcomed their newborn baby Noah Shannon Green in September.
Watch a trailer for This Is 40 below:
Photo Gallery: Golden Globes Press Room
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