How Long Does It Take to Form a Habit? The 'Three-Week' Rule

The impulses firing across synapses, or spaces between certain cells that guide communication in the brain, govern everything we do (and think, for that matter). When we repeat any behavior or pattern enough, the synaptic pathways associated with that pattern get used to being accessed.

As a result, it becomes easier for impulses to travel along those pathways, and the behavior seems "natural." In other words, to the brain, wake-coffee-cigarette, in that order, is practically instinctive. One action triggers the next.

So when someone tells you, as many self-help gurus might, that the habit formation process occurs in three weeks, it's natural to be skeptical. Why specifically three weeks? And how could you form a new instinctive behavior in such a short period of time?

No one is entirely sure where the 21-day rule originated, but a book called "Psycho-Cybernetics" seems to have set forth the idea. It's a self-help book first published in the 1970s, and in it, you find out you can create or break a habit in just 21 days.

The problem is, the evidence supporting the theory is empirical, or based on experience, not clinical, or based on controlled experiments [source: Benefit].

The theory caught on, though, and others have backed it up since then. In 1983, for instance, a woman chronicled her journey to create positive habits — namely to start flossing and stop criticizing — in "Three Weeks to a Better Me," an article for Reader's Digest.

But does it really work for everyone, or are these just the experiences of a couple of individuals?

The reality is that it is easier to form a new habit than it is to break bad habits. If you repeat new behaviors often enough, those synaptic pathways are going to get worn in. The human brain is a very adaptive piece of machinery. But does that take 21 days? Who knows? Everyone's brain is different, and habit forming also relies on aspects of experience and personality.

Breaking a habit is a lot more complicated because while parts of those worn-in pathways can weaken without use, they never go away [source: Rae-Dupree]. The slightest provocation can reactivate them [source: Delude]. If you've ever tried to quit smoking, you already know this. You can go a year without a cigarette, and then give in one time and BAM, the habit comes right back.

The best you can do, then, is to form a new, parallel pattern, like exercising when you feel stressed, rather than indulge in the old pattern, which triggers "cigarette" in response to stress.

So what about these 21 days?

If you've ever tried to break any habit at all, you can get a good feel for the reality of the 21-day rule by examining the following statement made by the "Self Improvement Mentor":

Or in this statement made by the writers of the self-help book "The Secret," referring to a variation of the habit rule that says it takes 30 days:

Wow, really?

Changing a habit is never that simple. If it were, those struggling with food would have healthy habits, alcoholics would never relapse, and everyone would adhere to a healthy diet 100 percent of the time.

For most people, staying away from a bad habit is a lifetime effort, backed up by the fact that those well-worn synaptic pathways never go away. There's no apparent scientific reason why it would take three weeks to break an old habit or make a new habit.

Depending on your unique physical and mental health, it could take a few weeks, it could take five days or it could take nine months.

Building habits is not easy, but there are some steps you can take to increase your chances of success in the endeavor, including:

[source: Newby-Clark]