Sometimes we struggle to discover why we're the way we are.
There are people who believe they're naturally caring or miserable or just sensitive -- whatever that might mean.
Now a scientific study has come along to explain, at least to some extent, why people are moody.
It seems to be quite simple: those born in the winter tend to be placid, friendly, lovable adults. Those born in the summer, however, are allegedly prone to be the moody snivellers whom we tolerate at our own peril.
This, at least, is how the Telegraph reports a piece of research from Hungary.
It quotes the gloriously named Xenia Gonda, lead researcher on this project, as saying: "Biochemical studies have shown that the season in which you are born has an influence on certain monoamine neurotransmitters, such as dopamine and serotonin, which is detectable even in adult life. This led us to believe that birth season may have a longer-lasting effect."
Gonda, a professor in the Department of Clinical and Theoretical Mental Health at Semmelweis University in Budapest, declared: "We can't yet say anything about the mechanisms involved. What we are now looking at is to see if there are genetic markers which are related to season of birth and mood disorder."
I wanted to see whether Gonda was the moody type, as this might have affected the way she presented her findings. I could only discover that she was born in 1976. I contacted Gonda, who was thankfully in the mood to explain a few things (she did admit that she's a little moody and that she was born in March).
Firstly, she told me that the effects are much more visible at the population level than the individual level.
She explained just how the seasons might affect humanity: "Season of birth determines several influences which effect the fetus in the mother's womb during gestation while the central nervous system develops and also during the first few months after birth which are also crucial. Season of birth and season during each of the trimesters determines -- and used to determine especially up to the last century -- what foods and nutrients were available, how much physical activity the mother had, what pathogens were in the environment, temperature, light which strongly influences circadian rhythm, which in turn influences a range of phenomena and is thought now to play a key role in depression."
There may be genetic factors at play too.
"Season of birth does not only determine a vast array of environmental effects but may also be related to genetic factors related to mood. Very simply, take seasonal affective disorder, which has been linked say to a polymorphism in the serotonin transporter gene with a small effect," Gonda told me.
"Those parents who have SAD are more depressed during late autumn and winter, therefore hypothetically less likely to procreate during late autumn and winter. Which means that since they may also pass proneness to SAD and also this gene variant onto their kids, these kids will be more likely to be conceived from spring through early autumn therefore to be born from mid winter to early summer. This was actually found in another study by another group," she continued. "So you won't get SAD because you're born in summer but you may be born in summer because your parents had SAD and you are more likely to have SAD because your parents also had it."
Life is, indeed, more complicated and more logical than one had feared. Gonda also mentioned to me that there is evidence that schizophrenics are more likely to be born in late winter to early spring.
You will surely be tempted to examine those around you to see if there might be some substance in the researcher's conclusions.
To get you started, I looked at the birth dates of famously placid people. Cuddly Brad Pitt was born on December 18. The serene goddess of a good life Oprah Winfrey was born on January 29. Pope Francis was born on December 17. So there you have it, the research has been vindicated.
There again, Steve Jobs was born on February 24, Christian Bale's birthday is January 30, Ann Coulter's is December 8 and Rasputin was born on January 24.
Should we conclude that all these people were or are, in fact, not moody at all?
What about the children of summer? Jon Stewart was born on July 22. Oh, so he's not all that much fun, is he? Larry David? July 2. Tom Cruise? July 3. Should we reassess the man who seems nice all the time, Tom Hanks? Well, he's a July 9 baby.
President Barack Obama was born on August 4, Fidel Castro on August 13. Could they have a meeting of (bad) moods, if not minds?
At heart, we don't often know what people are really like. The moods they express in public aren't all there is. So many factors seem to contribute to our being the way we are and feeling the way we feel.
Time can alter our behavior, even our feelings. Other people, too, can calm us and steer us.
Fortunately, I'm always sweetness and bliss, having been born on February 1. And if you believe that, you'll believe every piece of research ever performed.
Updated 734am with comments from Gonda.