There is little evidence of a so-called midlife crisis between the 1930s and 1970s.
"Middle-age is the time of growth that requires a process of adjustment," said Professor Nick Hissallam of the University of Melbourne.
Scientific studies have shown that older people choose middle age, as a stage they prefer in their lives.
"There is no middle point for life and crises, which can happen at any other time," he said. "It's hard to say when the midlife crisis should occur, since age concepts are flexible and change as we get older.
Evidence suggests that life is more positive in middle life, as personality becomes more stable.
A Swiss study, published in Gerontology in 2009, showed that with age, the middle-aged crisis increased among participants.
Psychologist Elliott Jack, who coined the term "midlife crisis" in 1965, believes it reflects the perception of death.
Others suggested that the term could be associated with children who were shunted out of the nest and had to take care of elderly parents. However, this situation can be biologically rooted.
One study found that reporting the midlife crisis was not recently associated with divorce, job loss, or the death of a loved one. In general, people go through a positive transition in what they consider their average life, says Professor Hissallam.
Psychological changes during middle age were found to be positive, with personality becoming more stable and self-acceptable, while positive emotion, on average, gradually increased during life.
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