Causes and Risk Factors of STDs

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In This Article

Sexually transmitted diseases are caused by intimate contact with an infected partner. According to the U.S. Centers for Disease Control and Prevention, more than 2 million cases of sexually transmitted diseases are reported each year in the United States.

The more sexual partners you have, the more likely you are to be exposed to an STD, but there are other risk factors as well. The type of sex and sexual partners you have, whether you practice safe sex consistently, previous history of an STD, and age all contribute to your risk of contracting an STD.

Common Causes

STDs are infections that primarily spread through sexual contact. There are a number of different STDs, such as herpes, chlamydia, gonorrhea, HIV, and HPV. Some infections are due to a viral infection and others are caused by a bacterial infection.

Rates of STDs are on the rise, the CDC reports. Between 2013 and 2017, cases of syphilis increased by 76%, gonorrhea by 67%, and chlamydia by 22%. New cases of HIV, however, declined between 2010 and 2016, with 38,700 new cases reported in 2016.

STDs are spread through body fluids, including blood, saliva, semen, vaginal secretions, and breast milk, or transmitted by direct skin-to-skin contact. Consistent use of condoms and other barriers can prevent STDs transmitted through body fluid, such as HIV and chlamydia, but may not offer protection against herpes and other diseases spread through skin-to-skin contact.

Your odds of contracting an STD depends on a number of factors, including:

  • How you have sex (manual, anal, vaginal, oral)
  • How many partners you have
  • What type of encounters you have
  • Whether you practice safe sex
  • How consistently you use condoms or other barriers
  • If you use barriers for intercourse only or oral sex as well
  • Whether you use lubricants and what kinds you use
  • Whether your partner has an STD and, if so, what type
  • The severity of your partner's infection (as measured by viral load and other factors)
  • Your overall health and the health of your immune system
  • Whether you have breaks in your skin, infections, or other STDs that make you more susceptible to infection

Lifestyle Risk Factors

There are many things that you can do to protect yourself against STDs. By being aware of the main risk factors that you can control, it's possible to stay healthy without having to resort to abstinence.

Here are common lifestyle risk factors for STDs and what you should know about each. 


People who are under the age of 25 are far more likely to be infected with STDs than older people for several reasons.

First, young women are more biologically susceptible to STDs than older women. Their bodies are smaller, and they are more likely to experience tearing during intercourse. Their cervixes also aren't fully developed and are more susceptible to infection by chlamydia, gonorrhea, and other STDs.

Finally, young people are more likely to engage in sexual risk-taking, particularly if they've been drinking alcohol, and are more likely to have multiple partners.

Alcohol Use

Drinking can be bad for your sexual health in many different ways. People who use alcohol on a regular basis, particularly in social situations, may be less discriminating about whom they choose to have sex with.

Alcohol also lowers inhibitions. It may also make it more difficult to convince a sexual partner to use a condom or to use one condom correctly.

Birth Control Pills

For many people, the biggest worry about having sex isn't STDs, it's pregnancy. Many heterosexual couples choose birth control pills as their primary form of contraception. However, once protected from pregnancy, some people are reluctant to use condoms as part of their sexual routine. This can be because they are afraid of implying their partner has a disease. Or they may just not like using condoms. Dual protection – using both birth control pills and condoms – is the best option.

A History of STD

Having one STD frequently makes you more susceptible to infection by other STDs. Skin that is irritated, inflamed, or blistered is easier for another pathogen to infect. Having an STD is also an indirect reflection of your risk of new infection. Since you were exposed once already, it suggests that other factors in your lifestyle may be putting you at risk.

Illicit Drug Use

People who have sex under the influence of drugs are more likely to engage in risky sexual behaviors, such as having sex without a condom or other form of protection.

Drugs may also make it easier for someone to pressure you into engaging in sexual behaviors. Furthermore, injection drug use, in particular, is associated with an increased risk of blood-borne diseases such as HIV and hepatitis.

Multiple Partners

It's pretty straightforward math: The more partners you have, the more likely it is that you will be exposed to an STD. Furthermore, people with multiple partners tend to have partners with multiple partners, which compounds the risk.

Serial Monogamy

Some people only date one person at a time but still date a large number of people each year. This is referred to as serial monogamy.

The danger for people who practice serial monogamy is that each time they are involved in an "exclusive" sexual relationship, they are likely to be tempted to stop using safer sex precautions. But monogamy is only an effective way to prevent STDs in long-term relationships where both of you have been tested.

Since some tests aren't reliable until you've been infected for some time, many serially monogamous relationships don't last long enough for that to even be a viable option.


Homosexual and bisexual men, or other men who have sex with men, are disproportionately impacted by syphilis, HIV, and other sexually transmitted diseases (STDs).

In 2017, more than two-thirds of reported syphilis cases in both men and women were traced to men who have sex with men, the CDC reports.

According to a 2011 study published in the American Journal of Public Health, unprotected anal intercourse (for both men and women) increases the likelihood of contracting an STD because rectal tissue is more rigid and fragile than vaginal tissue. This makes anal tissue more susceptible to tearing, upping the risk of becoming infected. 

Trading Sex for Money or Drugs

People who trade sex for money or drugs may not be sufficiently empowered to negotiate for safe sex. And partners acquired in this manner are far more likely to be infected with STDs than people in the general population.

Note: Some sex workers, particularly those who have made an informed choice to enter their professions, are highly conscientious about safe sex and prevention. Risk varies according to individual behaviors, just as it does for people who don't engage in commercial sex.

Unprotected Sex

Although using a condom or other barrier method of birth control isn't a guarantee you won't become infected with a sexually transmitted organism, it's a highly effective way to protect yourself.

Even viruses like the human papillomavirus (HPV), which condoms are less effective against, have reduced transmission rates when condoms are used.

Other than abstinence, consistent condom use, which means using a condom every time you have sex, is the best way to prevent STDs.

Risk Reductions

Abstaining from all sexual contact is the number one way to prevent getting a sexually transmitted disease. However, that may not be practical.

You can reduce your risk of infection by getting regular STD screenings and talking to your partner before you have sex. Having this information can help you make smarter decisions about your sexual play. You can also reduce your risk by reliably practicing safe sex.

How to Reduce Your Risk

  • Use condoms correctly and consistently.
  • Have fewer sexual partners.
  • Discuss STDs with any sex partner you have.
  • Explore mutual monogamy.
  • Get vaccinated for HPV and hepatitis B.
  • Get tested for STDs and seek treatment if infected.
  • Encourage your sex partners to get tested.
  • Consider abstinence.

A Word From Verywell

Safer sex isn't a one-time thing. Ideally, it means using a barrier method every time you engage in sex, whether vaginal, anal, or oral. Barrier methods such as condoms or dental dams are not 100 percent effective. They do, however, dramatically decrease your risk of contracting an STD.

Only having sex within the context of a mutually monogamous relationship can also improve your odds of remaining STD-free. That's particularly true if both you and your partner continue to be regularly screened for STDs and have open communication about your test results.

Finally, remember that using a contraceptive may protect against pregnancy, but contraceptives don't necessarily protect against infections. Oral contraceptive pills and IUDs are great pregnancy protection, but they need to be used with barriers to protect against STD transmission. 

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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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