The 32-year-old comedian has persisted with her signature style of waistless dresses, space buns and Mary Jane shoes because she loved being a "six year old" and she still likes to be that person.
In an essay she has written for InStyle, she said: "I was everything I'd ever wanted to be (formidably adorable), everywhere I ever wanted to go (my bedroom) and hanging with the hottest company in town (my parents). So, like the high school quarterback who can't stop milling around the football field well into middle age, I have just continued to dress like a full-scale baby."
When Lena began to achieve mainstream success with her hit HBO show 'Girls' she was pressurised by people in her life to change her style and grow up but she resisted because it was not in keeping with her personality.
She explained: "When my career began to take off, I felt enormous pressure from parents, publicists, and pundits to start looking and acting like a real, live grown-up. The same thing I was celebrated for - my honesty and sense of self - was lambasted by those who felt celebrity (especially for women) meant a duty to appear camera-ready and probably sex-ready too."
Lena - who recently split from Jack Antonoff - insists her clothes can make her feel happy and reassured and her child-like style has helped her cope with many tough times in her life.
As well as the break-up, Lena had to undergo a hysterectomy to treat painful endometriosis, a procedure which means she cannot have children.
She said: "Through massive personal shifts, like my body's betrayal and a desperately public breakup, my baby clothes stood by me.
"Before my hysterectomy, I wandered the halls of the hospital in a frilled purple lounge set. I spent my first night alone in stretch mustard shorts and a T-shirt that read, 'I'm a very complicated child.'
"Being an adult is hard. You might as well go back to when your look soared as high as your youthful heart."