In the classic 80s rom-com Overboard, Goldie Hawn’s spoilt, selfish character suffers a brain injury in a yachting accident. As well as causing memory loss, the accident transforms her personality in positive ways – she becomes caring and considerate and less materialistic.

That a brain injury could lead to this kind of personality change may sound far-fetched, but consider the real-life “Patient 3534”, a woman who had a brain tumour removed at the age of 70, leaving damage to the front of both sides of her brain. According to her husband, who’d known her for 58 years, before her surgery she had a “stern” personality, was highly irritable and grumpy. After the brain surgery, he said that she was “happier, more outgoing, and more talkative than ever before”.

Patient 3534 is not the only one with such a change. There is now evidence that, at least for a minority of patients, beneficial personality changes are a reality, a revelation that is bound to prompt a new perspective on the impact brain damage has on personality.

Although it has long been known that brain damage can change personality, the literature has almost exclusively focused on personality impairments. Take the famous case of Phineas Gage, the 19th-Century railway worker who was described by friends as “no longer Gage” after an iron rod blasted through the front of his brain in a terrible accident. The once shrewd, intelligent man was said to have become aggressive and impulsive (although according to modern accounts, he later overcame these problems and started a new life as a horse carriage driver).

Similar to Gage’s story, there are also many modern published accounts of patients with damage to the front of their brains subsequently exhibiting disinhibited (socially inappropriate) behaviour, or even behavior that appears psychopathic.

 Patients with damage to an area important for emotions, were less prone to depression

But this negative picture “may only capture part of the story” according to a recent study in the journal Neuropsychologia. A team, led by psychologist Marcie King at the University of Iowa, found that out of 97 previously healthy patients who had suffered permanent damage to a specific area of their brains, 22 of them showed positive personality changes afterwards. Of the remainder, 54 had negative personality changes and the rest showed no change at all. These observations were based on asking a relative or close friend to rate 26 aspects of their personality before and after the injury. 

Past research has hinted at ways that damage to specific brain regions can sometimes have positive effects. For instance, a 2007 study of Vietnam War veterans found that those who had suffered damage to the areas thought to play a role in the development of post-traumatic stress disorder (regions involved in emotion and decision making) were less likely to have developed PTSD. Similar research found that patients with damage to an area important for emotions, were less prone to depression.

However, the new study is the first to document more wide-ranging beneficial personality changes in a large group of patients.

 What seemed relevant was a history of a difficult personality

As another example, take “Patient 2410”, a 30-year-old man who needed surgery after suffering a brain aneurysm. Both he and his spouse described how, pre-injury, he was short-tempered and prone to anger, and generally “mopey”. Post injury, by contrast, he laughs and jokes and is “more passive and easy going”. 

So what is going on, how can brain damage have such unexpected effects? The likelihood of a patient showing personality improvements seemed to be unrelated to gender, age, educational background or intelligence. Instead, what seemed relevant was a history of a difficult personality, such as a short temper and other negative traits, combined with a particular pattern of brain damage.

To understand this further, King and her colleagues scanned the brains of all of the patients. They found that those who showed personality improvements were more likely than the others to have experienced damage to the most frontal regions of the brain, the bilateral frontal polar region, which is important for taking other people’s perspective and decision making.

The methods, though, are highly exploratory and so the authors urge some caution. Their approach only allowed them to uncover broad patterns between brain damage and personality outcomes, and future research could help accurately identify which areas are associated with specific personality changes.

Their aim is often to dial-down brain circuits that are thought to be overactive in certain mental health conditions 

Also, while the personality changes for some patients were seen as positive, this shouldn’t be taken to downplay the seriousness of brain injury. Complete recovery from severe brain injury is extremely rare, and even when a patient appears fine on the surface, they may experience lasting hidden challenges, such as difficulty learning new information. Brain injury can also leave a person more vulnerable to further conditions like dementia.

It therefore seems incredible that brain damage can lead to beneficial personality changes. However, it doesn’t seem quite so outlandish when you consider that brain surgery is sometimes used as a last-resort treatment for psychological problems, such as obsessive compulsive disorder. This brings to mind the dark history of “Psychosurgery”, as it’s known, largely because of the overly-zealous use of crude frontal lobotomy by surgeons such as Walter Freeman in the middle of the 20th Century. However, as King and her colleagues note, modern techniques are more careful and refined, and their aim is often to dial-down brain circuits that are thought to be overactive in certain mental health conditions (for instance, there is evidence that depression is associated with excessive connectivity between frontal brain regions and other neural networks involved in cognition and emotions).

That the brain can be purposely tweaked in this way provides a clue as to how brain damage can sometimes lead to beneficial changes. In fact, some of the neural circuits targeted by modern psychosurgery are in the same part of the brain that was damaged in those patients who showed personality improvements in King’s new research.

These new findings also complement research into the neurological basis of personality, including the finding that extraverts are less sensitive to neural stimulation, for instance, or that highly agreeable people show more brain activation in regions involved in controlling negative emotion. It’s logical that by altering these kinds of neural patterns, brain damage might sometimes have paradoxically beneficial outcomes.

Our personalities reflect the essence of who we are 

It’s worth repeating, though, that brain injury (including “mild” concussion) should always be treated extremely seriously. Even in the rare cases of some apparently beneficial side effects, difficulties will nearly always be part of the clinical picture.

And while a positive personality change may seem welcome, remember that our personalities reflect the essence of who we are – it’s likely to be unsettling for patients and their friends and families to adjust to a personal transformation, even a positive one. That said, that a positive personality change is possible, shows that the story of what can happen after brain injury is more complex and surprising than many of us realised.

Dr Christian Jarrett edits the British Psychological Society's Research Digest blog. His next book, Personology, will be published in 2019.

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