Three couples had sex after spending an evening at the pub. The first couple had met for the first time that night. They desired each other sexually, not emotionally; in truth, they did not like each other all that much. The sex they had was physically satisfying and emotionally disconnected. The second couple liked each other very much, having dated for several weeks. The sex they shared that night was their first together and it was caring; they went to sleep that night feeling closer than they ever had before and knowing their relationship had changed. The third couple loved one another deeply and had been married for over a decade. The sex they had that night was physically thrilling, emotionally fulfilling, and psychologically comforting, the product of years of open conversation and practice.

Sex is a big deal. It is the closest two people can ever get to one another physically. The sex drive is the strongest urge we have as humans after our need for food and shelter. Evolution has designed sex to fulfill two purposes: to create new life and to promote emotional and social bonds between partners. Humans are one of a small percentage species that have sex for pleasure, with half of all Americans adults having sex at least two to three times per month (Blanchflower & Oswald, 2004).

Sex and Happiness

Blanchflower & Oswald (2004), a large study of 16,000 Americans, showed that there are strong links between sex and happiness. Unsurprisingly, this study revealed that people who reported having no sex in the past year were not as happy as those who reported having sex in the past year. When the researchers looked at the relationship between number of sexual partners and happiness, they found that the happiness-maximizing number of sexual partners in the past year was one; this means that people with two or more sexual partners in the past year tended to be less happy than those with one sexual partner.


Sex can have serious consequences that are far too easy to forget in the heat of the moment. Pregnancy is the most obvious consequence and it creates new life for a child and changes life forever for the parents. Of course, sex also carries a risk of acquiring a sexually transmitted disease (STD). Given recent advances in medical treatments, it is easy to fool oneself into thinking that STDs are not life changing but this simply is not true for millions of people living with incurable STDs such as herpes or HIV.

The use of contraceptives that reduce the risk of pregnancy and acquiring STDs is fortunately increasing; however, even amongst single adults, condoms are used in only 1 in 3 sexual encounters (NSSHB, 2010), highlighting the need for everyone to seriously consider the physical risks before engaging in sex.

Whereas the physical consequences of sex receive the most attention in public health contexts, the emotional consequences of sex, though often significant, are less commonly considered in discussion of high risk sex. Research shows that the interplay between sex and human emotions can be powerful (Birnbaum, 2006; Péloquin et al., 2013). In fact, two of the three most powerful predictors of sexual satisfaction (i.e., relationship satisfaction and the quality of sexual communication) require a significant amount of emotional connection, security, and commitment (see Péloquin et al., 2013 for a review).

Three Types of Sex

As a marriage and family therapist, I have an ethical obligation to help my clients make informed decisions about their sex lives when they decide to talk about them. Over the years, I have talked with hundreds of people about their sex lives and how to make them as healthy and satisfying as possible. One of the ways I frame these conversations is by talking with my clients about three types of sex. These sex types are distinguished by their degree of health risk and the partners’ level of commitment to one another, not the style of sex itself (i.e., position, duration). In my discussion on the three types of sex, committed couples are defined as those who are sexually monogamous and share an emotional attachment.

Type I.

Type I sex is had between partners who are not committed to one another. One-night stands are one example of Type I sex. The first couple in the vignette had Type I sex. As exciting as Type I sex can be, it carries the greatest risk because partners likely know little about one another: they can be less confident about their partner’s STD status, the devil-may-care nature of their relationship exacerbates emotional distress in the event of an unplanned pregnancy, and their lack of commitment could lead to confusion and heartache if one partner forms an emotional attachment and the other partner does not.

Type II.

Type II sex is had between people who are in a relationship but remain uncertain about their willingness to make a long-term commitment to their partner. Couples who are sexually active in an exclusive dating context are having Type II sex. The second couple in the vignette had Type II sex. When compared with Type I sex, Type II sex is less risky. If partners do not have STDs and remain sexually faithful, they can rest assured that they will not be infected. However, because couples in committed relationships are less likely to use condoms than couples in non-committed sexual relationships, there is an increased likelihood of pregnancy (Corbett et al., 2009).

Type III.

Type III sex is had between people who have made long-term, often lifelong commitments to one another. Sex in the context of marriage is an example of Type III sex. Type III sex has the lowest level of risk because these couples are likely to know their partner's STD status, they are comforted in knowing they are with person they want to raise children with in the event of pregnancy, and they desire strong emotional attachments with each other.

Three Questions

Having an understanding of the pros and cons of the three types of sex helps us make informed decisions about our sexual behavior. Because most of us will place considerable importance on having a healthy, satisfying sex life, we should not enter into a sexual relationship before we take the time to consider the consequences of our actions.

Before any of us engage in sex, we should ask ourselves three questions: (1) Am I willing to create and commit to raising a child with this person? (2) Can I trust that this person is not infected with an STD? (3) Am I prepared to potentially form an emotional attachment with this person? When answering these questions, we should remember that the human psyche evolved long before the invention of the highly effective contraceptives we have today. So although these contraceptives may prevent pregnancy and STD transmission, we may not be spared from the emotional effects of sex. Thus, we should not even consider having sex with someone if we cannot answer yes to all of these questions. These three questions take into consideration the three most important characteristics of sexual health from an evolutionary perspective and remind us that problems seem to crop up when a couple’s physical relationship is more intimate than their emotional commitment to one another.


In my next blog, I continue my discussion of sex by considering factors that distinguish a satisfying sex life from a dissatisfying, dysfunctional one.