"I was having crazy anxiety and having to show up for things that I didn't feel equipped to show up for," she continued. "But I know I need to do it, and when I take a Klonopin, I can do it."
According to WebMD, Klonopin (Clonazepam) is a benzodiazepine used to treat seizures, panic disorders, and anxiety.
The "Girls" star said the drug made her feel like the person she was "supposed to be."
"It was like suddenly I felt like the part of me that I knew was there was freed up to do her thing," Dunham said.
The actress, who's been open with her struggle with OCD and anxiety in the past, explained that she started abusing Klonopin by taking it more frequently.
"It stopped being 'I take one when I fly,' and it started being 'I take one when I'm awake,'" she said. "I didn't have any trouble getting a doctor to tell me, 'No you have serious anxiety issues, you should be taking this. This is how you should be existing.'"
Dunham went on to explain how she increased her dosage after also being diagnosed with PTSD from past sexual trauma.
"I was diagnosed with pretty serious PTSD," she recalled. "I have a few sexual traumas in my past and then I had all these surgeries and then I had my hysterectomy after a period of really extreme pain. It stopped feeling like I had panic attacks and it started feeling like I was a living panic attack. The only thing that was notable was the parts of the day where I didn't feel like I was going to barf and faint."
"If I look back, there were a solid three years where I was, to put it lightly, misusing benzos, even though it was all quote unquote doctor prescribed," she said.
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When Klonopin stopped working for her, Dunham realized she needed to wean off the drug. However, she was worried how much "worse" she would get without it. Having other health issues like endometriosis, Dunham has been on her "fair share" of painkillers, but said that the withdrawal from Klonopin was so severe to the point that the smell of prescription pill bottles now makes her sick.
"Nobody I know who are prescribed these medications is told, 'By the way, when you try and get off this, it's going to be like the most hellacious acid trip you've ever had where you're f--king clutching the walls and the hair is blowing off your head and you can't believe you found yourself in this situation," she said. "Now the literal smell of the inside of pill bottles makes me want to throw up."
The Golden Globe winner said that she speaks about her past addiction because she knows that she's "not alone." Although she's now 6 months sober, Dunham explained that she is still recovering.
"I still feel like my brain is re-calibrating itself to experience anxiety," she added. "I just feel literally on my knees grateful every day."