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Actually, It Doesn't Take 21 Days to Form a Habit — A Neuroscientist Explains

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May 2, 2021
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Some behaviors are easier to develop than others, but there's this pervasive idea that it takes 21 days to form a habit. The notion can be traced back to a book published in 1960 by cosmetic surgeon Maxwell Maltz, M.D.—and after selling over 30 million copies, the observation practically became gospel.

But according to communication pathologist and neuroscientist Caroline Leaf, Ph.D., BSc, the ideal length of time isn't 21 days—it's actually triple that. "Habits don't form in three weeks; they form in nine weeks," she declares on the mindbodygreen podcast. Below, she describes what really goes on in the brain when you're integrating a new practice.

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Why it takes nine weeks to form a habit.

Don't scratch the 21-day time frame completely! It's not totally random: The three-week mark is, in fact, significant when it comes to habit formation—it just represents the beginning stages.

"It takes three weeks to get gamma peaks in the brain, which means that we can reconceptualize [thoughts]," she explains. Imagine these brain waves as smaller tides on a beach—they're important, as they allow for new connections to flow, but they're fleeting.

So these gamma peaks are an important start, but the brain needs more time. Leaf sums it up this way: "In order to make [the waves] strong enough to impact behavior change, we need another 42 days."

She has the research to back it up, too. She conducted a clinical trial on millennial anxiety and tested their brain waves on Day 1, Day 21, Day 63, and points in between. "Some of our [participants] who were clinically depressed had a totally flat, blue brain at the beginning of the study—which means very low, like a flat line in the sea," Leaf explains. "Once they had mind management, the brain had gone gray within three weeks, which means the waves were flowing properly." By the end of nine weeks? "It was sustainable."

Leaf isn't the only expert to regard anxiety as a habit—it can be mindless, after all, and it may take some awareness to break the pattern. Theoretically, the same science can apply to any other bad habit, not just those anxious thoughts swirling through your brain. However, she notes another vital—and encouraging—aspect to remember when it comes to habit formation: You might not consciously realize the effects in the beginning.

"You may not feel the changes happening in you as you're doing mind management at first," she says. "But the research shows that your non-conscious mind and your body know before you do, so the changes will happen in your brain." You'll just have to trust the process for a time—well, nine weeks, to be exact.

The takeaway.

While 21 days marks an important step for forming a new habit, according to Leaf, a full nine weeks is the key to making sustainable change. If you are looking to introduce a new practice into your life or, perhaps, let go of something that no longer serves you, don't feel alarmed if it's not smooth sailing by the three-week threshold. It may just take a little more time for the new habit to stick.

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