Mid-life crisis
Midlife crisis is a term used to describe a period of dramatic self-doubt that is typically felt in the "middle years" of life, as people sense the passing of youth and the imminence of old age.  Sometimes, transitions experienced in these years, such as aging in general, menopause, the death of parents, or children leaving home can trigger such a crisis. The result may be a desire to make significant changes in core aspects of day to day life or situation, such as in career, marriage, or romantic relationships.
Academic research since the 1980s rejects the notion of midlife crisis as a phase that most adults go through. In one study, less than 10% of people had psychological crises due to their age or aging. Personality type and a history of psychological crisis are believed to predispose some people to this "traditional" midlife crisis. People going through this suffer a variety of symptoms and exhibit disparate behaviors.
Many middle aged adults experience major life events that can cause a period of psychological stress or depression, such as the death of a loved one, or a career setback. However, those events could have happened earlier or later in life, making them a "crisis," but not necessarily a midlife one. In the same study, 15% of middle-aged adults experienced this type of midlife turmoil.
Some studies indicate that some cultures may be more sensitive to this phenomenon than others. One study found that there is little evidence that people undergo midlife crises in Japanese and Indian cultures, raising the question of whether a mid life crises in mainly a cultural construct. The authors hypothesized that the "culture of youth" in Western societies accounts for the popularity of the midlife crisis concept there.
Researchers have found that midlife is often a time for reflection and reassessment, but this is not always accompanied by the psychological upheaval popularly associated with "midlife crisis".

# Occurrence
For the approximately 10% of middle aged adults who go through an age-related midlife crisis, the condition is most common ranging from the ages of 35-50 (a large study in the 1990s found that the average age at onset of a self-described "mid-life crisis" was 46). Mid life crises last about 3-10 years in men and 2-5 years in women.
A midlife crisis could be caused by aging itself, or aging in combination with changes, problems, or regrets over:
- work or career
- spousal relationships
- maturation of children
- aging or death of parents
- physical changes associated with aging
Midlife crisis seems to affect men and women differently. Researchers have proposed that the triggers for mid-life crisis differ between men and women, with male mid-life crisis more likely to be caused by work issues.
Some have hypothesized that another cause of the male mid-life crisis is the imminent menopause of the female partner and end of her reproductive career. This renews the need for the man to attract younger women.

# Characteristics
Individuals experiencing a mid-life crisis are said to have some of these feelings:
- search of an undefined dream or goal
- a deep sense of remorse for goals not accomplished
- desire to achieve a feeling of youthfulness
- need to spend more time alone or with certain peers
They are said to exhibit some of these behaviors:
- abuse of alcohol
- conspicuous consumption -- acquisition of unusual or expensive items such as clothing, sports cars, jewelery, gadgets, tattoos, motorbikes, etc.
- depression
- paying special attention to physical appearance

# Theoretical Basis
Although mid-life crisis has lately received more attention in pop culture than serious research, there are some theoretical constructs supporting the notion. Jungian theory holds that midlife is key to individuation, a process of self-actualization and self-awareness that contains many potential paradoxes. Although Carl Jung did not describe midlife crisis per se, the midlife integration of thinking, sensation, feeling, and intuition that he describes could, it seems, lead to confusion about one's life to date and one's goals. Later, Erik Erikson held that in life's seventh stage, middle adulthood, people struggle to find new meaning and purpose to their lives; their questioning, he believed, could lead to what we now call a midlife crisis.

# Criticism
Some people have challenged the existence of mid life crises all together. One study found that 23% of participants had what they called a "mid-life crisis," but in digging deeper, only one-third of those -- 8% of the total -- said the crisis was associated with realizations about aging.
The balance (15% of those surveyed) had experienced major life experiences or transitions such as divorce or loss of a job in middle age and described them as "midlife crisis." While there is no doubt these events can be traumatic -- the associated grief reactions can be indistinguishable from depression -- these upheavals aren't unique to middle age and aren't an age-related midlife crisis.
University of California - Davis researchers Carolyn Alwin and Michael Levenson presented the current view of midlife crisis in a 2001 article:
Costa and McCrae (1980) found little evidence for an increase in neuroticism in midlife ... While they did find that some people were likely to experience such crises, ... these individuals were likely to experience crises in their 20s and 30s, and these experiences were not unique to midlife.
...Robinson, Rosenberg, and Farrell (1999) reinterviewed (500) men. Looking back over their midlife period, it became evident that while not necessarily entailing crisis, it was a time for reevaluation."
Wrapping up their review of men's midlife crisis, Alwin and Levenson wrote that "... Given the bulk of the data, it is likely that, for most men, midlife is a time of achievement and satisfaction. For a certain proportion of men, however, the passage is not at all smooth." They found a similar pattern when they reviewed research on what are commonly thought to be triggers for women's midlife crisis: menopause, children leaving home, the "sandwich" of caring for both parents and children. Most women navigated those periods without a traumatic psychological "crisis."
The enduring popularity of the midlife crisis concept may be explained by another finding by Robinson et al. As Alwin and Levenson summarize: "... younger men, now middle-aged Baby Boomers, used the term "midlife crisis" to describe nearly any setback, either in their career or family life."
Levinson's findings were research about the possible existence of a mid-life crisis and its implications. Whereas Levinson (1978) found that 80% of middle-aged participants had a crisis, and Ciernia (1985) reported that 70% of men in mid-life said they had a crisis (Shek, 1996) others could not replicate those findings including Shek (1996), Kruger (1994), and McCrae and Costa (1990). The debate of whether or not there is a mid-life crisis is being answered through recent research that attempts to balance such things as response bias and experimenter effects in order to establish internal validity. The above mentioned research does not support Levinson's model of a single age in the middle years that is a designated time of transition and potential "crisis."
For the most part, at all ages researchers in Positive Adult Development have found improvement or at worse stasis for most of the population.