When thinking about midlife crises, it's not uncommon to imagine silver-haired men riding a Harley home to their much younger partner. But this time period, which we believe to be marked by self-doubt and emotional hardship, may be a complete illusion, according to a recent study published in the journal Developmental Psychology.

Happiness tends to increase with age, thanks to better health, job security, and marital bliss, the study authors from the University of Alberta (UAlberta) argue. It doesn't follow a U-shaped curve in life, but rather it continues to slope upward even through midlife. Harvey Krahn, sociology professor at UAlberta, said in a press release that "if you want to see how people change as they get older, you have to measure the same individuals over time." Previous studies, meanwhile, have only measured participants' happiness at the time they were being observed.

Krahn and his colleagues, however, followed a total of 1,500 Canadians who were split into two cohorts: high school seniors who were followed for 25 years until age 43, and university seniors who were followed for 14 years until age 37. The goal of the study was to measure individual happiness over time, so participants were asked the same question at different ages: "How happy are you with your life?" Other questions focused on the state of participants' health and whether they were married or unemployed, among others.

The findings revealed happiness levels among both groups increased well into their 30s. Overall, participants were happier in their early 40s than they were at age 18 — even if the high school group started to experience a slight drop around age 43.

The researchers suggested happiness increases from a person's adolescence to midlife, because some young adults have difficulty finding work and getting their life on track. While earlier years may be filled with uncertainty, these issues tend to be solved by middle age. What's more, as many people age, they also achieve certain life milestones, such as obtaining better health, job security, and marriage.

Aside from the aforementioned factors, happiness is also contingent on an individual's mental attitude. A 2013 study found extraverted, emotionally-stable young adults were more likely to be happier in retirement than those who kept to themselves or experienced emotional ups and downs in early adulthood. This suggests personality characteristics in youth have an enduring effect on well-being decades later.

It's important to remember these are just tendencies; better health, job security, and marriage can influence our outlook on life, but this is subjective. It's all about figuring out what makes us happy and being positive we can improve the less-than-thrilling aspects of life.

Sources: Galambos NL, Fang Sm Krahn HJ et al. Up, not down: The age curve in happiness from early adulthood to midlife in two longitudinal studies. Developmental Psychology. 2015.

Gale CR, Booth T, Mottus R et al. Neuroticism and Extraversion in youth predict mental wellbeing and life satisfaction 40 years later. Journal of Research in Personality. 2013.