Marc Lewis Ph.D.

Addicted Brains

The Rise and Fall of Craving

We can outsmart the relapse tendency if we know how it works.

Posted Dec 14, 2017

A couple of years ago I came across a paper in Addiction Biology called "Recent updates on incubation of drug craving: a mini-review." The studies it summarized show that drug craving has a distinct timetable. I want to review and comment on these findings. They can be immensely valuable if you're trying to stay recovered.

The paper reviews research on rats as well as humans. And why not? We're all mammals and we share a lot of the same neural hardware. But while we have a similar "motivational brain," humans have other problems that make rodent life look like easy street. We have this enormous cortex (linked to a hippocampus that fills it with zillions of explicit memories), and so the cues that trigger craving often come from, and are magnified by, our own ruminations. That can be a real drag.

Most of the studies in this review involve rats. In a typical study, rats get themselves addicted to cocaine, meth, or heroin (with considerable help from humans), and then their supply is cut off. After the withdrawal period is over, the rats are given cues that are associated with the drug they were on. These are called "conditioned stimuli" in Pavlovian conditioning. Then the experimenters measure how much the rats crave the drug  (based on how often they take it, or how much they hang out in the place where it gets delivered) in the days and weeks that follow. The craving goes up, not down, as time goes on. And then finally it peaks and diminishes several weeks later.

The first thing to note is that the craving is always "cue-induced." It is literally triggered by a sight or sound (a green light or a buzzer) that previously meant "Come and get it!"

The second thing to note is that the incubation period (the period of increasing craving) is longer than we might like, but it's not forever. Typically 10 days to a few weeks for rats. For humans, undoubtedly longer (in one study, it peaked at 60 days abstinence for alcoholics; in another, it peaked at three months for meth users).

It's very important to realize that craving in the absence of cues decreases much more quickly, often beginning almost immediately after quitting. That's a great rationale for hanging out on your uncle's farm in Idaho for a few months after quitting.

Berridge lab, with permission
Source: Berridge lab, with permission

What's going on in the rat's brain that makes it vulnerable to cue-induced craving? The amygdala is the main culprit, and the nucleus accumbens is its partner in crime. The amygdala registers emotional significance. If something is emotionally meaningful, whether the emotion is fear, anger, desire, or whatever, the amygdala will increase its firing. This is where the cue starts the process of emotional arousal and readiness. Then the nucleus accumbens takes over (stoked by a tide of dopamine). The nucleus accumbens is the part of the brain that produces an urge go after a goal: it narrows attention to the goal, gives you that feeling of "I really want it", and then activates behaviors...like prancing to the part of the cage where the coke gets dispensed, if you're a rat, or picking up the phone and calling your dealer, if you're a human.

If you're a rodent, that's all it takes. Craving is a learned emotional response. You've learned that something felt really nice, and it might be available, and because your brain is efficient and determined, you're going to go after it. By the way, rats on a high sugar diet show very much the same response once they're cut off. So we're not just talking about drugs.

But what if you're a human? I assume you are if you've read this far. Then you've got a whole other set of problems. The initial cue can be the hands on the clock, telling you it's about that time. It can be a mental image, a rumbling in your gut, the ragged touch of rising depression, an image on TV. It can be a baggie, an email, a neon sign, a dream. So far, you're just a very intelligent rat. You just got a surge of dopamine to your nucleus accumbens; you're alert, wanting, wishing...but you're also thinking, and that's where things get much worse.

Musee Rodin, by permission
Source: Musee Rodin, by permission

You're thinking that the day feels so empty without it. What am I going to do with my time? Thinking that there's really nothing that can fill that gap. Thinking maybe that you deserve it, or you deserve how shitty you're going to feel tomorrow, or both. One thought leads to another leads to another, and these thoughts fill your head. The amygdala and accumbens both connect to many many parts of the cortex, and they literally unleash these thoughts, which then trigger other related thoughts through direct synaptic connections. That's rumination — the pathway to craving.

The problem is that the habit you've developed isn't just a learning and feeling habit; it's a thinking habit. And until you start to become accustomed to living without that thing, those habits have little to replace them.

So, it would be ideal to avoid cues, but that's just not entirely possible since they can come from anywhere (including your own brain). In which case, you have to work on your thinking habits until thought patterns readjust and the cue-trigger starts to lose its force (this can take weeks or months for humans).

But how do you work on those ingrained habits of thought? There are many ways. Two come to mind immediately:

1. Shift your thinking as soon as you start to ruminate. Don't even wait ten seconds. You can turn off cascades of thinking far more easily before they build momentum.

2. Fill your days with other attractive, compelling activities. Provide your day with contour: a beginning, middle, and end, so that the rumination habits don't have so much traction.

LakeView Health, with permission
Source: LakeView Health, with permission

But there's one more highly valued strategy, and in this, you're no different from a rat: Get connected to others when you quit. Cue-induced craving is greatly reduced by "environmental enrichment" for rats and for humans. Remember Rat Park? Interpersonal, social activities are incredibly powerful cues for humans as well as rats, and they can drown out the cues connected to drug-taking.

And one more thing: Be brave.

References

Li, Caprioli, & Marchant (2014). Recent updates on incubation of drug craving: a mini-review. Addiction Biology, vol. 20, pp 872–876.  

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