There is an certain age where people start to do crazy things. Things like cheating on their partners.

Well, there are several ‘certain ages’ but they all have one thing in common.

They’re all birthdays ending in nine. It seems turning 19, 29, 39… really, any age right before a round number causes people to display dramatic, destructive behaviours.

Which is frightening for me, because yesterday I turned 29.

I didn’t really consider it to be a particularly significant birthday. But it seems I was wrong.

Age Isn’t Something to be scared of. It’s a privilege

Proceedings of The National Academy of Sciences has published an article which indicates that just before people enter a new decade, they start reflecting deeply and questioning whether their lives hold appropriate meaning. If they don’t perceive their stage of life to be suitable, the potential for damaging, life changing behaviours is escalated.

“Years 30, 40, 50, they’re psychologically consequential… They seem big, they seem looming and they seem more important to us than the others. They make us step back and think about how things have been going up until then and how we want them to go moving forward.” Hal Hershfield, a research psychologist at UCLA, who co-authored the paper, told the Washington Post.

It all sounded pretty deep to me.

The research included six independent studies, with a total of 42,000 participants from over 100 countries, and analysed emotional and psychological changes in people on the cusp of a round number birthday.

Things like undertaking physical challenges like triathlons ( I have no such plans) cheating on partners (definitely no such plans) or even taking our own lives (no) were all more likely to happen on the cusp of a new decade than at any other life stage.

Using a fitness website which tracks running times, the research found that people "in the nines" are 25 per cent  more likely to run their first marathon, and those who ran multiple marathons tracked faster times than they had in previous years, suggesting they were training harder.

Researchers also used cheating dating website Ashley Madison (which essentially creates a forum for married scumbags to link up with other married scumbags).

They found that men and women who registered on the website seeking extramarital affairs were 18 per cent more likely to be aged 29, 39, 49 and 59.

While I have absolutely no desire to run marathons, have affairs or end my own life, I have spent my 29th birthday reflecting back on my twenties, and just the other day I decided I "needed a change" and lopped off all my hair.

I don't see a haircut as necessarily a way of searching for meaning in my life but part of it was linked with a fresh approach, assessment of where I'm at, and an adoption of a more level headed mentality I'd like to possess as I move into my thirties.

I guess, in my case, Dr Hershfield was right.

What do you think? Have your birthdays ending in '9' been a big deal?