People are most depressed in middle age, research on two million people from 80 nations finds.
In the US, the risk of depression peaks at around 40-years-old for men and around 50-years-old for women.
In the UK, the highest probability of being depressed is at age 44.
The causes of mid-life depression are hard to explain, as they happen to all kinds of people.
For example, it doesn’t seem to be related to marriage, divorce or having (or not having) children.
Professor Andrew Oswald, study co-author, explained:
“Some people suffer more than others but in our data the average effect is large.
It happens to men and women, to single and married people, to rich and poor, and to those with and without children.
Nobody knows why we see this consistency.”
The researchers found a U-shaped curve between happiness and age.
In other words, people were happiest when they were young and old, but their happiness dropped in between.
Professor Oswald said:
“What causes this apparently U-shaped curve, and its similar shape in different parts of the developed and even often developing world, is unknown.
However, one possibility is that individuals learn to adapt to their strengths and weaknesses, and in mid-life quell their infeasible aspirations.
Another possibility is that cheerful people live systematically longer.
A third possibility is that a kind of comparison process is at work in which people have seen similar-aged peers die and value more their own remaining years.
Perhaps people somehow learn to count their blessings.”
Professor Oswald said that those living to 70-years-old and beyond could look forward to feeling as happy as a 20-year-old, on average:
“It looks from the data like something happens deep inside humans.
For the average person in the modern world, the dip in mental health and happiness comes on slowly, not suddenly in a single year.
Only in their 50s do most people emerge from the low period.
But encouragingly, by the time you are 70, if you are still physically fit then on average you are as happy and mentally healthy as a 20 year old.
Perhaps realizing that such feelings are completely normal in midlife might even help individuals survive this phase better.”
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The study was published in the journal Social Science & Medicine (Blanchflower & Oswald, 2008).