For those struggling to shake the memories of some awkward teenage years, take heart, because it looks like your body isn't the only thing to undergo massive changes through adulthood - your personality can shift dramatically too.

The longest running personality study ever has revealed that our personality changes so much from youth to old age, on paper, you might look like a completely different person from when you were 14 and 77 years old.

Researchers from the University of Edinburgh in the UK analysed the results from a 1947 study that recruited 1,208 teenagers in Scotland aged 14, and got their teachers to assess their personality. 

The teachers were asked to fill out six different questionnaires that assessed the students on six traits: self-confidence, perseverance, stability of moods, conscientiousness, originality, and desire to excel. 

These results were then condensed into an overall rating for a single underlying trait called "denoted dependability" - a trait comparable to conscientiousness. 

Now, more than six decades later, the University of Edinburgh team managed to contact 635 of the original students, and 174 agreed to have their personalities tested once more.

At an average of 76.7 years old, the group was asked to rate themselves on the six personality traits, and nominate a close friend or family member to do the same. 

This time, the group completed seven personality scales and tests, and had their mental health assessed. The results were once again condensed into a single "dependability" score.

When the researchers compared the results at 77 years to those at 14 years, they found no notable correlation.

"[T]here were no positive correlations strong enough to achieve significance between adolescent and older-age characteristic ratings or dependability," the team concludes.

"We hypothesised that we would find evidence of personality stability over an even longer period of 63 years, but our correlations did not support this hypothesis, appearing inconsistent with previous results."

Even when the team ran the data through a more complex model that took into account the effects certain 'raters' could have had on the results, they found only a "fairly low" correlation from 14 to 77 in the conscientiousness and stability of moods traits, and no correlation between the other traits.

The results were a surprise, because previous research has found personality stability in people tested from childhood to middle-age, and from middle-age to older age.

But the researchers suggest that because we undergo many small changes in personality over a lifetime, studies that only asses personality traits over part of a lifetime could miss the bigger picture.

As the team explains:

"As a result of this gradual change, personality can appear relatively stable over short intervals - increasingly so throughout adulthood. However, the longer the interval between two assessments of personality, the weaker the relationship between the two tends to be.

Our results suggest that, when the interval is increased to as much as 63 years, there is hardly any relationship at all."

There are some hefty caveats that need to be pointed out here, including the fact that the sample size is very small, and not very diverse, and the original study did not allow the participants to rate themselves, so the results relied solely on their teacher's opinion of them. 

There are also problems in general with studies that involve self-reporting, or any kinds of assessment that could be influence by bias - either by the teacher towards the student at 14 years old, or the friend or family member at 77 years old.

And the researchers were only looking for links between personality results, not the causes that could affect why our personality traits might change throughout life, so further research is needed to help us make sense of all of this.

But the results support the findings of a 2014 study of more than 23,000 individuals in Germany that revealed the personality of older people can change at a similar rate as that in young adults.

That study found that up to 25 percent of the study participants underwent a dramatic personality change after the age of 70.

"Unlike among young adults, the personality changes in older individuals did not follow a recognisable pattern," said one of the team, Jule Specht from Freie Universität Berlin, in 2014.

More studies are needed to figure out what's going on here, and if we can confirm this personality change over the majority of a human lifespan, we need to figure out why it's actually occurring.

But it could be the first sign that it's not just our cells that are being constantly replaced throughout life - the way we think, behave, and emote might not be as set in stone as we once thought.

The research has been published in Psychology and Ageing.