Obesity, drug addiction, and dopamine

Eating junk-food can be addictive, and apparently, it causes brain changes that look eerily similar to drug addiction. That’s the message not only from the rapidly fattening waistlines of Americans everywhere, but also from the Johnson and Kenny labs at the Scripps Institute.

Food and drug addiction

The idea that obesity is caused by a compulsive pattern of eating, and that there could be a similarity between such compulsive eating and drug addiction isn’t super new. In fact, Dr. Volkow from NIDA seemed to make research into this association her goal when taking  the helm of the addiction research kingdom.

When you think about it, the notion isn’t far-fetched: Drug addicts continue to take drugs, in increasing amounts, even though they’d often like to stop (at some point) and in the face of negative consequences and the common loss of other important life functions (like family, work, etc.). Obese individuals are quite the same, eating more and more food regardless of their desire to adopt a healthier diet and in-spite of ridicule, low self-esteem, and decreased functioning that often accompanies extreme weight gain.

The research by Johnson and Kenny examined whether exposure to the kind of high-fat, super high-calorie foods that floods the junk-food market are responsible for creating food-addicts in a similar way to drugs that alter the brain in ways that make stopping more difficult.

Dopamine, reward, and junk-food

The study took three groups of rats and gave them either the regular chow diet lab animals are used to or the worse kind of birthday party food: bacon, sausage, cheesecake, pound cake, frosting and chocolate. You can imagine the party going on in the rat cages that got to eat that! Of the two groups that got to eat the crazy-fat food, one had unlimited access while the other got to binge for only one hour a day.

The bottom line: Only the rats that got unlimited access to the fat-party food developed compulsive eating habits that resulted in roughly twice the weight gain of the other two groups and the ability to continue eating even in the face of signals for punishment (a light that they were trained to associate with shocks).

When the researchers looked deeper, they found that the brains of these rats suffered a significant reduction in the density of a specific kind of dopamine receptor (D2) in a brain part known as the striatum, the same kind of reduction common in drug addicted people and obese individuals. This receptor type is often thought to be important for regulation of impulses, both physical and otherwise. It therefore makes sense that losing this type of function would cause uncontrollable eating or drug taking.

Are drug- and food-addictions the same?

While this research isn’t saying that compulsive eating, or obesity, are the same as drug addiction, it does strongly suggest that there are common mechanisms in both. More importantly, it reveals a common process that unfolds when over-exposure to the reward, in this case food, occurs. This tells us that there can likely be common pathways to these different addictive disorders, though whether any specific person ended up a food- or drug-addict because of this kind of process is still an open question. I wonder if we’ll see something like this with sex addiction soon…

Citation:

Johnson and Kenny (2010) Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats. Nature neuroscience, 13, 635-641.

Helping Addicts with medications for cravings

If we could make it so drug addicts could stop craving the substances that have brought them to their knees, would relapse rates drop and addiction-treatment success rates soar? I sure hope so!

Medications that stop cravings?

I’ve already written about a study by the renowned addiction researcher Barry Everitt showing that medications could be used in treatment to help addicts who are struggling with strong cravings and the effect of triggers (see it here). Still, in that study the researchers used a drug that blocked pretty much all memory formation and my original idea had to do with using a very common drug, one being used every day for hypertension, and more recently, in the treatment of PTSD.

Well, a study recently completed revealed that indeed, propranolol, a common beta-blocker, may be useful in greatly reducing the amount of time needed to overcome the sometimes crippling effect of triggers on behavior.

How this trigger to cravings study worked

The researchers trained rats to take cocaine, and after they were well trained, allowed them to press a lever for a light that had previously been associated with the drug. This is a common method to test the way animals react to triggers that have been associated with the drug. Even though the animals are no longer getting any cocaine when the light goes on, the fact that it had been previously associated with the drug makes the animals press the lever, like an addict triggered by something they’ve associated with their drug use.

The animals that were given propranolol immediately after every session took half as long to stop pressing for the drug-associated light. It took multiple administrations of propranolol (seven to be exact), but the effect was clear. The next step is to see if the same effect can be observed in people.

Helping addicts transition to outpatient substance abuse treatment

I’ve been claiming for the past few years that if we look in the right places, we can find many ways to help struggling addicts who are having a hard time quitting using currently available methods. I think that the notion that sticking to the “best method we have right now” is unwise given the fact that science has progressed quite a bit in the past 20-30 years. I agree, and am thankful, that the system works for some, but there’s no question that many still have trouble recovering from addictions that devastate their own lives and the lives of many close to them. I think these medications can offer some serious help.

The thing is, that if we could seriously reduce the impact of cravings on relapse rates, it’s possible that addicts would be ready to move from residential to outpatient substance abuse treatment  more quickly. Indeed, the main reason for keeping people in residential treatment is the thinking that they’re not ready to be in the world given the influence of triggers. My guess is that this is true for some addicts, but if we could provide an intervention, like propranolol, that would significantly reduce the influence of triggers, outpatient substance abuse treatment, which is a cheaper option, will be useful for many more. This would mean more people in treatment that truly works for them for less money. Sounds good to me.

Citation:

Ashley N. Fricks-Gleason & John F. Marshall (2008). Post-retrieval ß-adrenergic receptor blockade: Effects on extinction and reconsolidation of cocaine-cue memories. Memory & Learning, 15, 643-648

Drug use memories and relapse: Can medication provide addiction help?

About a year ago, while sitting in a lecture on learning and memory, the idea that certain drugs can affect the emotional responses to memory long after the memory itself has been formed came up. As someone interested in addiction research, the implication for treatment immediately came up in my head:

Could we reduce the effect of triggers by giving people a pill?

In one word – Yes! But, the answer is not, in fact, that simple. Even in the studies already done in PTSD patients, the memories have to be re-triggered and the drug given at exactly the right time to be effective. In fact, in humans, some of the best work has been done in PTSD patients immediately after the traumatic event.

Addiction help through relapse prevention

Still, a recent study in animals suggests that the theory is sound. By interfering with the activity of a neurotransmitter important in the formation of memories, researchers were able to stop animals trained to self-administer cocaine from doing so. The animals, which had been trained to push a lever for cocaine when a light went on, reduced, or even stopped responding after a single dose of a substance that blocked memory formation. Essentially, the researchers prevented the animals from relapse. Again, this only worked if the drug was given while the light (as in the drug-trigger) was presented at the same time.

More recent studies, using repeated doses of the drug propranolol, have been shown to have an even more promising effect. Check out my coverage of that research here.

Given the powerful role of triggers in relapse, this avenue of research has some promising possibilities for future treatment of drug addiction.