This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

Women experience higher stress, more chronic disease, more depression, more anxiety and are more likely to be victims of violence. Women earn less than men, and in many countries they don’t have the same human rights as men.

Despite the social inequality women experience, they live longer than men. This is the case without a single exception, in all countries.

For instance, in the U.S. in 2015 female full-time workers made only 80 cents for every dollar earned by men, indicating a 20 percent gender wage gap. Yet, life expectancy for women in the U.S. is 81.2 years compared to 76.4 for males.

Even in countries with larger wage gaps or extreme gender inequalities, women live longer than men.

As a researcher who studies cross-country and gender differences in health, I am always fascinated by how the intersection of these factors influences health. So why do women live longer, despite their lower social rank and worse health?

Is it basic biology?

Gender refers to social aspects of being a woman or a man such as social stress, opportunity and social expectations.

Sex, on the other hand, refers to biology. Biology can contribute to this difference in life expectancy. Women have biological advantages that let them live longer.

For instance, estrogen benefits women because it lowers low-density lipoprotein cholesterol (or LDL, what you may know as "bad" cholesterol) and increases high-density lipoprotein cholesterol (or HDL, the "good" cholesterol), which reduces cardiovascular risk.

Testosterone, on the other hand, increases blood levels of the bad cholesterol and decreases levels of good cholesterol. This puts men at greater risk of hypertension, heart disease and stroke.

When it comes to chronic diseases, women tend to have more of them. But there is a caveat here. Men and women have different types of chronic disease. Women have more nonfatal, chronic conditions, while men have more fatal conditions.

For example, women have more arthritis, which does not kill, even if disabling. In contrast, men are at higher risk of chronic diseases that are leading killers. Heart disease starts 10 years earlier in men than women.

So, biological differences play a role in this life expectancy gap, but gender, I argue, plays a bigger role.

Women are more health aware

Studies have shown that, in general, women are more health conscious, and they have higher awareness of their physical and mental symptoms. These all result in healthier lifestyles and better health care use. Women also communicate better about their problems, which helps the process of diagnosis.

Being a man means delayed initiation of treatment of any kind. Men are less adherent to treatment.

These issues collectively cause males to be vulnerable to therapeutic failure.

Masculinity is a socially learned construct, and it can have unhealthy effects. Many men define unhealthy and risky behaviors as masculine, while they see health care use and health-promoting behaviors as feminine.

Risky behavior and sensation-seeking

Testosterone puts men at risk biologically, but it also puts men at risk behaviorally. It increases aggressiveness, and, in a cascading effect, results in higher death rate from accidents and homicide.

My colleague and I followed more than 250 youth and found that baseline testestrone predicts future violent behaviors.

Women systematically overestimate risk of any type, while men consistently underestimate it. This pattern has been observed regardless of the context. These include examples ranging from crossing a road to perception of risk of volcano, smoking or a terrorist attack. Among pedestrians, males violate more rules than females. Among drivers, men more commonly break the rules.

Accidents, like motor vehicle crashes, are far more common among men than women. This is due in part to men’s greater risk-taking, underestimation of risk, sensation-seeking, and tendency to be more impulsive.

This difference extends to almost any task in real life. This in part explains why women internalize and men externalize (which requires low perception of risk).

Substance use is also more common among men than among women. While that gap is narrowing, according to a 2011 study, men were 2.2 times more likely to abuse drugs than women, and 1.9 times more likely to have drug dependence.

Among those who have drug use problems, men tend to have more severe problems, defined by frequency of use, using more than one substance and risky behaviors such as injection drug use. Men with drug use problems seek care later than women do. Men also drive under the influence of drugs and alcohol more frequently than women. Men are responsible for four out of every five cases of driving under the influence of a drug or alcohol.

So why do men have a higher tendency to abuse illicit drugs and alcohol than women?

This is in part due to sensation-seeking, which makes some men search for experiences and feelings that are varied, novel, complex and intense. Higher acceptability for men of risky behaviors, peer pressure and gender roles also have a role. Although some of this may be due to testosterone levels, a considerable part of it is due to learned gender roles.

In addition to higher sensation-seeking, men have more impulsive traits and have higher thresholds for punishment.

And our previous research has shown that masculinity plays a role for depression and alcohol use.

Suicide

In most countries, men are more likely to die by suicide. In the United States, for example, men are 3.5 times more likely than women to die from suicide. This is mainly because men use more lethal methods for suicide, such as firearms.

In the U.S. most suicides are white men. In fact, suicides among this group are one reason why mortality for middle-aged white American men is increasing.

One reason behind the high suicide rate among men is the high stigma about psychiatric disorders as well as mental health care use. So when men experience stress they are at higher risk of mental health problems such as depression than women, possibly because they do not talk about their emotions and they do not seek care. Such a tendency to avoid mental health care is directly related to masculinity, gender norms and social expectations for men.

Unemployment is a major cause of suicide globally and in the U.S. Unemployment may have a bigger role as a cause of suicide for men, as it results in a larger "human capital loss" among men than women.

Thinking about gender

Our gender can determine how our parents treat us, which in turn make us learn to behave in a certain way, as dictated by societal beliefs, values, attitudes and examples. Boys and girls start facing social norms that define "masculine" and "feminine" for them from an early age.

Gender differences in mortality are mainly behavioral and thus preventable, as they are learned in society and manifested in behavioral and psychological ways. Although our brain is involved, it is not in our genetics. It is learned socially and it can be unlearned.

Gender differences are rules rather than exceptions. While in many factors, women do worse than men, in the case of life expectancy, men do worse. Theese are mainly due to a wide range of social, psychological and behavioral factors such as sensation-seeking, risk-taking traits, stigma, masculinity, worse health care use, and a tendency for externalizing behavior. Males require more self-control, stigma reduction (by mass media) and incentives to seek and use professional care.

Shervin Assari, Research Investigator of Psychiatry and Public Health, University of Michigan

This article was originally published on The Conversation. Read the original article.