You Can’t ‘Erase’ Bad Memories, but You Can Cope With Them

The film Eternal Sunshine of the Spotless Mind pitched an interesting premise: what if we could erase unwanted memories that lead to sadness, despair, depression, or anxiety? Might this someday be possible, and do we know enough about how distressing memories are formed, stored, and retrieved to make such a therapy possible?

Cognitive behavior therapy (CBT) is a common treatment for anxiety disorders. The basic idea of CBT is to change the fear-eliciting thoughts that underlie a client’s anxiety.

Imagine, for instance, a person who has a dog phobia. They are likely to believe that “all dogs are dangerous.” During CBT, the client is gradually exposed to friendly dogs to cognitively reframe their thoughts or memories into something more realistic—such as the belief “most dogs are friendly.”

CBT is one of the most scientifically supported treatments for anxiety disorders. But unfortunately, a recent U.S. study indicated around 50 percent of patients saw fear memories resurface four years after CBT or drug treatment. Put another way, the old fear memories seem resistant to being erased through therapy or drug treatment.

Why Distressing Memories are Difficult to ‘Erase’

Fear memories are stored in the part of the brain called the amygdala. Having a healthy dose of fear keeps us safe from dangerous situations that might reduce our chances of survival.

Permanent storage of dangerous information is adaptive. While we might learn some things are safe sometimes, like encountering a lion in a zoo, we also need to be aware that those same things may not be safe in other times, like meeting a lion in the wild.

This permanent storage of a fear memory explains why relapse occurs. During therapy, a new memory—most dogs are friendly—is formed. But this new safe memory is bound to a specific context—friendly dog in the therapy room. In that context, the rational part of the brain, the prefrontal cortex, puts a brake on the amygdala and tells it not to retrieve the old fear memory.

But what happens when a patient encounters a new context, such as a dog in a park? By default, the brain retrieves the fear memory that “all dogs are dangerous” in any context, except the one where the new safe memory occurred. That is, old fear memories can be renewed with any change in context.

This default has helped humans survive in dangerous environments throughout our evolutionary history. However, for anxious clients whose fear is unrealistic and excessive, this default to distressing memories is likely one important basis for the high rates of anxiety relapse.

So Is Erasure Ever Possible?

There are a few instances that suggest “erasure” is sometimes possible. For example, relapse is not seen early in life with animals. This may be because of the brake signals from the prefrontal cortex to the amygdala mature late in development. As there are no brakes, perhaps fear memories are erased instead.

By extension, this suggests early intervention for anxiety disorder is important as children may be less likely to relapse. However, the jury is still out on whether erasure of fear memories occurs at all in children and, if so, at what age.

So, given the high rate of relapse, is there a point to pursuing treatment at all? Absolutely. Having some respite from anxiety allows for significant moments of sunshine and improves quality of life, even if it is not eternal. In these moments, the typically anxious person might attend parties and make new friends or handle a stressful job interview successfully—things they would not have done because of excessive fear.

One way to reduce the chances of relapse is to confront irrational fear at every opportunity and create new safe memories in many different contexts. Anticipating contextual factors that are trigger points for relapse, such as changing jobs or relationship break-ups, can also be adaptive. Strategies can then be used to manage the re-emergence of distressing thoughts and memories.

While erasing negative memories may be the goal of the characters in Eternal Sunshine, the film also emphasizes the importance of these memories. When processed rationally, stressful memories motivate us to make better decisions and become resilient. Being able to look back on unpleasant memories without excessive distress allows us to move forward with greater wisdom and this is the ultimate goal for all therapeutic frameworks.

Carol Newall is a senior lecturer in early childhood at Macquarie University in Australia. Rick Richardson is a professor at UNSW Sydney. This article was first published on The Conversation.