Monday, September 7, 2009

Reward and punishment in anorexia nervosa

A recent review article titled "Theoretical perspective on anorexia nervosa: The conflict of reward," has to be one of the most fascinating scientific reads I've had for a long time (and my Facebook friends can confirm that I read a lot!). The gist of the paper is that many of the behaviors of AN, such as food restriction and excessive exercise, are initially rewarding, they eventually become punishing. An overlap in the neural circuits that process reward and punishment enables these two factors to become all knotted up, or "contaminated."

The author, Charlotte Keating, begins her argument with the concept of anhedonia, or an inability to experience pleasure, which is central to both major depression and a clinical feature of AN. Moreover, excessive exercisers tend to report greater levels of anhedonia, perhaps because exercise is being misused as a mood elevator. Initially, exercise and food restriction are very rewarding, which may be partly why people with AN become entrenched in these behaviors in the first place. Not eating feels better. Exercising feels better. Continued food restriction and excessive exercise only reinforces the reward, leading to the expectation that not eating and over-exercising will make the person with AN feel better.

The problem, says Keating, is that food restriction and excessive exercise are ultimately rather punishing behaviors. So how can punishing behaviors simultaneously be rewarding? The answer appears to lay in the anterior cingulate cortex, which (among many other things) is involved in the processing of reward, punishment, conflict, empathy, and other rational cognitive behaviors. In people with AN, the ACC doesn't process reward the same way; whether ultimately derived from dopamine circuits, reward is blunted in people with AN.

Writes Keating:

"...it may be that hypoactivity in ACC (which reflects the bulk of literature investigating this region in AN) reflects an impaired ability to adjust maladaptive behaviors which may also lead to illness maintenance."

Thus reward-punishment contamination means that the AN sufferer has a greatly reduced capacity for motivation to change, and to regulate his/her pathological behaviors. Furthermore, a low motivation for change only increases the neural "blurring" between reward and punishment.

The ultimate goal is not only to improve motivation to change by decreasing the blurring between reward and punishment in AN sufferers, but also to target "the mechanisms that may be responsible for bringing about behavior modification."

(cross posted at ED Bites)

2 comments:

Nancy said...

I am not entirely sure how I found your articles but they are amazing. Please tell me the best way to continually receive them.

My question is: what is the treatment for bringing about behavior modification in the blurring of reward and punishment and to treat what Keating discusses "...it may be that hypoactivity in ACC (which reflects the bulk of literature investigating this region in AN) reflects an impaired ability to adjust maladaptive behaviors which may also lead to illness maintenance."

What is the most succesful treatment for the depression controlling ED and other maladaptive behaviors paired with ED and influenced by depression?

Carrie Arnold said...

Nancy,

The best treatment for AN is food (you can see the video by Dr. Tim Walsh where he says this here. CBT has been found to decrease relapse after weight restoration in AN- I can probably dig that study up if you want me to.

If you have a blog reader, you can subscribe that way (I use Google reader, you can sign up at reader.google.com and read all your blogs that way). I will add a feature tomorrow to the blog where you can have new posts emailed to you automatically.

Hope this helps. I'm not allowed to do much in the way of exercise right now, so PubMed is my favorite new sport! LOL