One study in the research we highlighted here found that less than a quarter of middle-aged respondents experienced what they felt was a midlife crisis -- and for many of those, the crisis was not associated with aging. More detail is in this article, where one of the researchers emphasized that an age-related midlife crisis is not that common -- but midlife challenges are: »more»

A relatively old (1999) Washington Post article reports on several large studies that found midlife to often be a period of "smooth sailing" with an "increased sense of control." Among the findings: the stereotypical "midlife crisis" is often associated not with age, but with significant life events that just happen to occur between youth and old age: »more»