Adultery is commonly defined as engaging in sexual intercourse between a married person and a person who is not their spouse.

Based on data from the National Opinion Research Center survey in 2014, 17 per cent of women in marital relationships have committed adultery compared to 25 per cent of men.

In the Barometer of modern morals published by the Pew Reserach Center, a whopping 88 percent of repsondents deemed adultery, or cheating on one's spouse morally wrong, and something they consider far worse than cheating on taxes, alcoholism, smoking marijuana, and abortion, among other things.

And yet, it continues to happen, which leads to the question: why do married couples enage in adulterous acts? 

An article from Divorce Statistics explain that women who commit adultery are often seeking an emotional connection that they feel is lacking from their partner while for the men who enter into extramarital relationships are more inclined towards the sexual aspect of the affair.

Even economic depression was cited as a trigger for this behavior , according to analysts. 

Interestingly, one study found that men are more likely to feel guilt over a sexual affair, while women feel more guilt over emotional adultery.  The common factor, however, was feelings of guilt.  

The leader of the study, Maryanne Fisher, a professor at St. Mary's University in Halifax, Canada, feelings of guilt were diminised among those who were more motivated to cheat in the first place.

"In these instances, people seem more capable of justifying their actions to themselves, which reduces feelings of guilt," she said. 

Whatever the justification the guilty parties can come up with, there are negative emotional consequences.  

While committing adultery may seem right at the time it is being committed by the married individual, family planning specialist Dr. David Gelvin warns in an article on Netdoctor that there is a negative psychological impact to be had.

Some of the resulting issues are:

• Intense guilt or depression. These feelings, according to Dr. Gelvin will affect the person who has committed adultery, which brings a lot of emotional baggage into the marriage. Couples counseller Brett Kahr even suggests that the cheater may in reality actually want their adultery to be found out, similar to a cry for help.
• Deep distress and distrust in the 'betrayed' partner. Learning that your spouse has been unfaithful causes anguish and grief and disharmony in the relationship. An OnlyMyHealth post also said that infidelity leads the aggrieved party to question themselves and results in insecurities about their supposed failings in the relationship.  It can take years to rebuild the trust that has been broken.
• A futile cycle of blame or vengeance.  Instead of facing up to the underlying causes and part that both partners may have played in the breakdown of the relationship, writes relationship expert Kate Figes.  Similarly Figes says it's important that the injured parties do not have knee-jerk reactions as this can encourage the unhelpful formation of a victim vs. villain dynamic that pushes both sides into defensive positions and makes it harder for the real issues to be addressed.
• Violence. Dr. Gelvin warned that there are still reports of spouses killing cheating partners, otherwise known as crimes of passion.  
• Marriage break-up. In some cases, relationships do not survive infidelity as trust is completely lost in the relationship.
• Unhappiness in the couple's children. Emotional distress is not just limited to the husband and the wife. For those who have children, this also affects them psychologically.

Based on a study, conducted by clinicians in 1989, children feel it when their parents are expending emotional energy outside of their family even if they are not able to prove it, leading to a sense of rejection. The lingering sense of fear and anxiety also makes them prone to having an affair when they get married.

Dr. Annette Lawson, a sociologist formerly affiliated with the Institute for Research on Women and Gender at Stanford University said of the study: "It was something the parents apparently did not care to confront."

She added: ''Even though they may swear they will never do the same, it appears to become a patterned reponse learned in childhood."