Is it true that it takes 21 days to form a habit

Whatever it is you’ve resolved to do in the new year — floss! Become an a.m. exerciser! Stop the late-night snacking! — the conventional wisdom is that it’ll take 21 days to make the new behavior a habit. Even Jay-Z and Beyonce believe it; it's what their December adventure in veganism was based on.

It would be really nice if on Jan. 21, after three faithful weeks of skipping dessert, the idealistic behavior became automatic. But scientists who study habit formation say it’s not that easy. There isn’t a magic number — and even if there were, it would be more like 66 days, according to one recent study, which means getting out of bed early to go for a run isn't going to come easy until March at the earliest.

On average, it took people 66 days for a new healthy habit to feel automatic — things like eating a piece of fruit with lunch, or drinking a glass of water after breakfast, found the 2010 UK study, led by University College London research psychologist Pippa Lally. The data was self-reported, which means there’s a chance the people weren’t totally accurate, or honest. And the time it took for the habit to form varied widely: For some people, the healthy habits felt automatic after just 18 days — for others, it took 254 days.

“So this does not mean it always takes 66 days, but it does mean that it is usually much longer than 21 days,” Lally said in an email to TODAY Health.

The “21 days to form a habit idea” seems to have come from a 1960 self-help book by cosmetic surgeon Dr. Maxwell Maltz, called “Psycho Cybernetics, A New Way to Get More Living Out of Life,” says Wendy Wood, a University of Southern California psychologist who studies the way habits guide our behavior. “He recommended that people practice self-affirmations and positive behaviors for 21 days to make them habitual,” Wood says. “He thought that it would take about 21 days of practice for an old mental image of ourselves to dissolve and a new one to ‘gel’ (in his words).”

In the decades since the book was published, the “21 days” idea has been repeated so often that it’s become accepted as fact. But to make a new habit, you're really asking your brain to learn a new behavior, and it takes more time to learn some tasks than others.

“To understand how silly it is to target a number like 21, consider the variety of behaviors that become habits,” Wood said in an email. “Some are complex, like keyboarding and reading, and these can take years of practice to develop proficiently. Others are quite simple, such as using a new coffee maker you got for the holiday.”

Forming a habit is simple — but that doesn't mean it's easy. Here's some advice and insight from the experts:

1. Time and place are key. Repeat the same action at the same time and the same place, until it becomes automatic. “So, if you practice going for a walk every evening when you get home from work, then after a while, when you enter your house, thoughts of going for a walk spring to mind,” Wood says. “Any evening, you can always decide not to go, but usually, given how tired and distracted we are, it’s easier to carry out the response in mind than to make a decision to do something else.”

2. Figure out your cue. Maybe you eat ice cream on the couch every night, and you'd really like to stop. Rather than trying to quit cold turkey, try to figure out what's triggering the ice cream. "It's being not just aware of the behavior, but understanding what things happen before that that might put your unconscious mind into that state where it's going to go to the refrigerator. Is it a particular television show, or a particular time of night?" says David Neal, a social psychologist who has studied habit formation and habit breaking. "In a way, the behavior is not the problem; the cue is the problem."

3. It's easier to form a new habit than break an old one. It's really hard to stop late-night snacking, but it's easier to replace that behavior with something else. David Neal suggests replacing it with another activity to occupying your hands: "Like knitting ... although, people don't knit anymore, do they?"

Bonus 2014 resolution idea: Take up knitting.

From daily tooth-brushing to the 11am coffee, we all have dozens of habits that get us through our daily routine.

Some are great - weekly gym visits are often encouraged - others not so much, like smoking a pack a day, or dialling the number of the pizza place way too often.

Because we recognise our habits as useful or detrimental behaviours, we often strive to shape them accordingly.

There's no shortage of apps out there designed to help you form a habit, and many of those are built on the assumption that all you need is 21 days.

This number comes from a widely popular 1960 book called Psycho-Cybernetics by Maxwell Maltz, a plastic surgeon who noticed his patients seemed to take about 21 days to get used to their new faces.

However, according to a 2009 study, the time it takes to form a habit really isn't that clear-cut.

Researchers from University College London examined the new habits of 96 people over the space of 12 weeks, and found that the average time it takes for a new habit to stick is actually 66 days; furthermore, individual times varied from 18 to a whopping 254 days. 

The take-away message here is that if you want to develop a new behaviour, it will take at least two months, and you shouldn't despair if three weeks doesn't do the trick - for most people that's simply not enough.

Stick with it for longer, and you'll end up with a habit you can keep without thinking.

But what about trying to break an unwanted habit? 

It turns out the two - habit forming and breaking - can be quite closely linked.

As psychologist Timothy Pychyl explains to Alison Nastasi at Hopes and Fears, they're two sides of the same coin: "Breaking a habit really means establishing a new habit, a new pre-potent response. The old habit or pattern of responding is still there (a pattern of neuron responses in the brain), but it is less dominant (less potent)."

"It's much easier to start doing something new than to stop doing something habitual without a replacement behaviour," says neuroscientist Elliot Berkman.

"That's one reason why smoking cessation aids such as nicotine gum or inhalers tend to be more effective than the nicotine patch."

Experts agree that there's no typical time frame for breaking a habit, and the right recipe is going to be a mix of personality, motivation, circumstances, and the habit in question.

"People who want to kick their habit for reasons that are aligned with their personal values will change their behaviour faster than people who are doing it for external reasons such as pressure from others," says Berkman. 

According to psychology professor Susan Krauss Whitbourne, sometimes a habit can be broken quickly: "In extreme cases, the habit can be broken instantly, such as if you happen to become violently ill when you inhale cigarette smoke or nearly get hit by a bus when texting and walking."

But in most cases it's going to take longer than that, and you should probably allow for at least two months.

To successfully break a habit, you need to think of your strongest motivation, which will drive you along.

Think of a 'replacement behaviour' for the habit, but make sure it's a positive one - replacing smoking with snacking is a common trap, for example.

And be patient. The longer you've had a habit, the longer it will take to get rid of it.

"Longtime habits are literally entrenched at the neural level, so they are powerful determinants of behavior," explains Berkman.

"The good news is that people are nearly always capable of doing something else when they're made aware of the habit and are sufficiently motivated to change."

So stay strong, you can do it. 

A version of this article was first published in September 2015.

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