The Black Mirror Pill: Propranolol and the Science of Forgetting

Some readers may recall the 2014 Black Mirror episode ‘The Entire History of You’. An implant ‘remembers’ everything we see and do, allowing us to access these memories in complete detail as many times as we like (not far off from replaying that particularly embarrassing thing you did in middle school when you can’t sleep at 2am). Driven mad by the fact that his wife cheated on him, the main character uses a blade to cut the implant out of his brain — effectively erasing any memories he hadn’t stored in his own mind. Albeit not an implant, propranolol, the medication prescribed for heart pain, migraines, and anxiety, could be used to do something similar. Propranolol works by dimming the body’s biological response to adrenaline and norepinephrine (the chemicals the body releases in response to stressful stimuli). In people using it to medicate anxiety, it lowers the heart rate, making breathing easier and calmer. 

When the body releases norepinephrine and adrenaline during moments of stress, it can ‘over-solidify’ the memory of that event in our minds. This often causes the body to react to triggers resembling the original event as if reliving it. Picture a sole survivor of a car crash avoiding cars of the same make or taking detours around a specific stretch of road. Experiments in the therapeutic use of propranolol have shown promising results in weakening the emotional intensity of traumatic memories, thus also lowering the intensity of the body’s response to recalling the memory.   

Gradually softening the emotional strength of the memory makes it easier to ‘forget’ it in the kaleidoscope of other memories we hold. In participants living with PTSD, the drug reduces their physical reactions to recalling a traumatic memory. Interestingly, the effects of the drug appear to strengthen with time instead of hitting a ceiling — a finding which has significant implications for propranolol’s potential as a course of medication. It also loosens the intensity of the first impression the memory makes; indeed, one 2013 study found that participants who ingested propranolol before watching a gory video struggled to clearly remember the details of the video. More recently, in 2021, a study found that the drug was effective in helping participants unlearn and, crucially, resist redeveloping a specific fear response. Indeed, the vast majority of research thus far promises propranolol to be a promising treatment for people living with severe and complex trauma, as in PTSD or phobias.   

That being said, propranolol is only the latest in a line of memory-altering drugs, and the debate around the importance of authentic memories has raised several questions. In his 2011 article in Nature, neuroethicist Adam Kolber argues that the adverse reaction to memory-altering drugs is exaggerated, premature, and, most importantly, stalling further research which charts a path to the problems at the centre of the debate. 

Are the emotions we feel when recalling our past an evolutionary mechanism to keep us from repeating our mistakes? How crucial are our memories to our core identity? Indeed, maybe the right question is not whether we would like to forget instead of remember, but whether we can be trusted to live without our ghosts.      

Image by Wikipedia Commons