How Common Is Incest? A Close Look at the Statistics [2024]

We did our research and gathered some interesting facts on how common incest is: its history, its types, risk factors, and psychological harms. Read on:

Sex is one of the most powerful and formative aspects of the human experience. While it can be empowering and euphoric under the right circumstances, it can also be devastating and painful under the wrong ones. 

That’s why most of us tend to keep sex outside of the family. Family members who engage in sexual activity with each other are committing an act called incest, and in most cases, it’s nonconsensual and psychologically scarring. 

We did our research and compiled a wealth of data on the prevalence, laws, history, and effects of incest. 

Here are some highlights from the available data on incest:

• Stepdaughters are over 8 times more at risk of sexual abuse by stepfathers than by biological fathers.
• Incest is legal between consenting adults in the states of New Jersey and Rhode Island, but marriage is illegal. 
• Colorado has the highest maximum fine for incest of any state – $750,000, in addition to 2 to 12 years in prison.
• In one study, 93% of women who had been incestually abused by their fathers developed eating disorders. 100% experienced depression. 
• Single-mother families with another man living in the home (not the father) are three times more at risk for father-daughter incest. 
• Mother-son incest is the least common type of incest reported. 

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What Is Incest?

You’ve probably heard of incest, but it may be a little different than you think. While the term incest might invoke images of redneck weddings or goofy stepfamily porn, in most cases, it’s much more serious than that. 

In most cases, incest involves the abuse of children or other family members. 

Incest – also called intrafamilial sexual abuse – is defined as sexual activity with a person in one’s immediate family. 

In simple terms, incest is sexual activity between family or close relatives. This typically includes blood-related people but can include relations from marriage, stepfamily, adoption, or lineage.

Incest is a common form of child sexual abuse. Most instances occur between older male relatives and younger female children in families of all demographics.

Sources: Patient, RAINN, Feminist

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How Common Is Incest?

One of the most difficult things to determine about incest is how often it actually occurs. Not every victim is willing to report their abuse, and results vary wildly depending on region and culture. 

Here’s the best data we have on the prevalence of incest worldwide:

The prevalence of child sexual abuse (not always incestual) is difficult to determine, and one study found it was between 6 and 62% for female children.

The prevalence of abuse depends on the definition. The broadest terms include extra-familial child sexual abuse (no incest), sexual abuse with or without physical contact, with or without violence, etc. 

Depending on culture, source of reporting, and location, the results of studies on the prevalence of incest range from 5% to 62%.

75% of perpetrators in the study were blood relatives (consanguineous), and 25% were not (stepfamily, adopted family, etc.). 

Mother-son incest was the least common type reported. 

One study of 296 incest cases involving father-daughter incest had the following results: 

Result

296 Incest Case

70

Perpetrators were the biological fathers of the victim.

87

Were biological relatives such as grandfathers, brothers, sisters, or cousins.

73

Were stepfathers. 

1.8% of female high school students in Istanbul, Turkey, reported being victims of incest.

One study found that sibling sexual abuse (SSA) is the most common form of sexual abuse within families.

One study found that the prevalence of intrafamilial (incestual) child sexual abuse was 18% for girls and 8% for boys.

One study pulled data from 217 publications and millions of participants; it estimated that overall, self-reported studies had a child sexual abuse prevalence of 127 per 1000 cases (12.7%), and informant studies had a prevalence of 4 per 1000 cases (0.04%).

 

Females

Male

 

Self-reported child sexual abuse was more common for

Females

18%

Male

7.6%

The highest rates of child sexual abuse

Percentage

For girls in Australia

21.5%

For boys in Africa

19.3%

This study is not specific to incestual child sexual abuse; while many instances in the study are incestual, some are not. 

Grenada noticed an increase in incest in 2020. From January to December 2018, they had 6 cases. During the same period in 2019, there 8 cases. As of September 2020, there were 56 incest cases.

• Sexual offenses increased overall during the Covid-19 lockdown period. 
• Police officials in Grenada expressed serious concern about the prevalence of incestual abuse toward children aged 13 to 16. 

One Swedish study looked at all child abuse in a specific area over a period of years and found the following data: 

Victims Gender

Percentage

Girls

85%

Boys

12% 

Involved Boys and Girls

3%

Sexual penetration occurred in 54.5% of cases. 

72% of perpetrators were well known to the child (i.e., relatives, family friends, etc.)

Biological relatives, family friends, or household members are significantly more likely to commit severe violations (sexual penetrations) than strangers. 

Sources: Zeitschrift fur klinische Psychologie, Psychopathologie, und Psychotherapie, Medical Science Monitor, Child Abuse & Neglect, Frontiers in Psychiatry, Evolutionary Psychology, Patient, Child Maltreatment, Now Grenada, Archives of Sexual Behavior

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History of Incest

While pre-historic humans may have found incest necessary for reproduction in some cases, the agricultural revolution and gravitation toward permanent settlement rendered the practice obsolete. 

Here’s a look at some of the incestual trends throughout history:

45,000 years ago, humans lived in communities so small that it was difficult to find someone to reproduce with who was not a relative.

In a study of the genetic makeup of 1,785 ancient humans, only 1 was found to have first-degree relatives (siblings or parent-child) for parents.

The royal families of ancient Egypt, Peru (Inca), and Hawaii engaged in incest to some extent.

Ancient China did not allow first cousins with the same surnames to marry; however, first cousins with different surnames could marry.

Several Egyptian kings married their own siblings.

• Arsinoe II married her younger brother, becoming the first in the Ptolemaic royal family to have a full-sibling marriage. 
• Tutankhamun married his half-sister and was himself a child of incest. 
• The Ptolemaic royal family was known for incest. For example, Cleopatra VII married two of her younger brothers, and her parents were also siblings. 

Greek law allowed marriage between siblings if they had different mothers.

In the first two centuries A.D., commoners in Roman Egypt engaged in brother-sister marriages frequently.

Sources: History of Yesterday, Nature Communications, The Journal of Sex Research, Sexual Life in Ancient China, Oxford University Press, Hellenic World Encyclopaedia

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Incest in the U.S.

Incest in the U.S. seems to have been largely overlooked as a problem before the 1980s. Incest is very closely tied to child sexual abuse, and most of the data on both subjects only comes from the past few decades. 

These data points highlight the extent of the incest problem in America:

In 1975, one text asserted that the rate of father-daughter incest in the U.S. was as low as 1 in a million families. Further research, however, revealed that it was much more common.

By 1986, another source estimated that father-daughter incest was as common as 1 in 20 families with a biological father and 1 in 7 families with a stepfather. 

Studies indicate that 160,000 women per million in the U.S. have been incestuously abused as children, and 45,000 per million were victimized by their fathers.

Data suggest that 1 in 3 girls, and 1 in 7 boys, are sexually abused before they turn 18 in the U.S.

Percentage

Sexually abused before they turn 18

14%

Of these victims are under the age of 6.

80%

Of these victims are incestually abused by family members

19%

Are abused by trusted adults.

Men are far more reluctant to admit abuse than women, so the percentage of abused boys may be much higher. 

Other studies estimate child sexual abuse may be as common as 54% of girls and 16% of boys. 

Sources: Psychiatric Times, U.S. Department of Justice, Medium, Journal of Spiritual Formation & Soul Care

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Types of Incest

There are different types of incest depending on the family members who perpetrate it. While there is consensual incest between related adults, most of it occurs when one or both individuals involved are underage. 

Here’s a breakdown of the different types of incest and their characteristics:

The most commonly reported form of incest is between adults and children. This is known as child incestuous abuse.

One study of adult women in San Franciso found that about 17% had been abused by stepfathers and 2% by biological fathers. 

The National Center for Victims of Crime reports that a staggering portion of rapes in the U.S. are perpetrated by a family member:

Percentage

National Center for Victims of Crime

46%

Children who are raped are victims of family members.

61%

American rape victims are raped before the age of 18. 

29%

All rapes occurred when the victim was under age 11. 

11%

Rape victims are raped by fathers or stepfathers; 16% are raped by other relatives. 

Sibling abusive incest happens commonly in families where one or both parents are either absent or emotionally unavailable. Incest is used by one sibling to assert power over the other. 

Absent fathers are a significant factor in cases where a female child is sexually abused by a brother. 

Female Victims

Depression

Substance Abuse

Eating Disorders

Female Victims

Brother-abused

Father-abused

Depression

100%

100%

Substance Abuse

56%

50%

Eating Disorders

80%

93%

Some parts of the world consider relationships between first cousins to be incestual, while other parts tolerate it.

First and second-cousin marriages are less than 1% of all marriages in Western Europe, North America, and Oceania.

• They are about 9% of all marriages in South America, East Asia, and Southern Europe.
• They’re about 50% of all marriages in the Middle East, North Africa, and South Asia. 

Sources: Rutgers School of Social Work, Psychology Today, Child Abuse & Neglect, Paediatrics and Child Health

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Risk Factors for Incest

Certain factors have been shown to increase the risk of incest in families. One of the most troubling risk factors is generational abuse. When perpetrators go unpunished, and victims go untreated, incest is likely to continue in a family through generations. 

The highest risk factor comes from unrelated fathers. Single mothers should never, ever invite a man to live at home with their daughter until they are absolutely sure he does not have abusive intentions. 

Here’s a look at the most prevalent risk factors for incest. 

Stepdaughters are over 8 times more at risk of sexual abuse by stepfathers than by biological fathers.

Disturbed family relationships create a shift in expectations or responsibilities that can lead to incest.

Percentage

Fathers (both biological and step)

34%

Fathers who sexually abuse their daughters are only likely to be present in the home during the daughter’s early childhood.

70%

Compared to non-abusive fathers.

Some studies suggest that incest “runs in families,” as incestual offenders are likely to have been sexually abused as children.

Risk factors for father-daughter incest include the following: 

• Families with parents who engage in verbal or physical fighting are five times more at risk of father-daughter incest. 
• Families with accepted father-daughter nudity are at increased risk. 
• Singe-mother families with another man living in the home (not the father) triple the risk of father-daughter incest. 
• The likelihood of father-daughter incest increases if a girl’s mother never or rarely hugs, kisses, or shows affection toward her. 

Sources: Patient, Postgraduate Medicine, Evolutionary Psychology, Clinical Psychology Review

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Incest and the Law

Incest is, predictably, illegal in all U.S. states when a child is involved and illegal in most states between adults. 

That being said, the laws and punishments vary by state. Here’s the data:

Incest is illegal in the majority of U.S. states, but punishments vary.

New Jersey and Rhode Island have legal incest so long as it occurs between adults. Marriage, however, is illegal. 

Here’s a breakdown of incest laws by state in the U.S., including the prison sentences and applicable fines:

State in the US

Prison Sentence

Applicable Fine

New Jersey

18 months to over 15 years

–

Rhode Island

No criminal prosecution for 16+

–

Alabama

1 to 10 years up

$15,000

Alaska

2 to 12 years up

$50,000

Arizona

1 to 3.75 years 

–

Arkansas

3 to 10 years

$10,000

California

up to 3 years

$10,000

Colorado

2 to 12 years up

$750,000

Connecticut

1 to 5 years

$5,000

Delaware

up to 1 year

$2,300

Florida

up to 15 years

$5,000

Georgia

10 to 30 years 

–

Hawaii

up to 5 years 

–

Idaho

up to a life sentence 

–

Illinois

2 to 10 years

$25,000

Indiana

1 to 6 years 

–

Iowa

up to 5 years

$7,500

Kansas

5 to 136 months 

–

Kentucky

5 years to life 

–

Louisiana

5 to 30 years 

–

Maine

up to 5 years

$5,000

Maryland

1 to 10 years 

–

Massachusetts

up to 20 years 

–

Michigan

up to 2 years

$500

Minnesota

up to 10 years 

–

Mississippi

up to 10 years

$500

Missouri

up to 7 years

–

Montana

up to a life sentence 

–

Nebraska

1 to 25 years

–

Nevada

2 years to life

$10,000

New Hampshire

10 to 20 years

–

New Mexico

up to 3 years

$5,000

New York

10 to 25 years

–

North Carolina

10 to 182 months 

–

North Dakota

up to 5 years

$10,000

Ohio

2 to 6 years

–

Oklahoma

up to 10 years

–

Oregon

up to 20 years

$375,000

Pennsylvania

up to 10 years 

–

South Carolina

6 months to 5 years

minimum $500

South Dakota

up to 15 years

$30,000

Tennessee

3 to 15 years up

$10,000

Texas

2 to 20 years up

$10,000

Utah

up to 5 years

$5,000

Vermont

up to 5 years

$1,000

Virginia

1 to 20 years up

$100,000

Washington

up to 10 years

$10,000

West Virginia

5 to 15 years

$500 to $5,000

Wisconsin

up to 40 years

$100,000

Wyoming

up to 15 years

$10,000

Criminal charges for incest vary by state and on a case-by-case basis:

• Incestual activity toward a child is considered a forcible sex act in all states and a form of child sexual abuse. Perpetrators can also be charged with sexual battery and/or assault. 
• Incest between adults is a felony, punishable by prison time and/or a fine. Incest against children is typically punished with lengthy prison terms. 
• People convicted of incest will likely have to register as sex offenders, especially if any crimes were committed against children. 

Sources: World Population Review, NOLO

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The Genetic and Psychological Harm of Incest

Incest is illegal for several reasons. First, inbreeding deals immense harm to the health of inbred children, and victims of incestual abuse suffer a psychological gauntlet of post-traumatic side effects. 

Here are the most prevalent ways that incest causes harm:

• The closer the two parents are related, the more likely their children will experience negative genetic defects.
• Sibling sexual abuse is often trivialized as normal sexual exploration but has been linked to psychosocial or psychosexual dysfunction.
• Women who experienced sexual abuse as a child have, on average, 16% higher annual health costs.

Victims of incest can experience the following psychological symptoms:

• Deliberate self-harm
• Nightmares
• Sleep disorders
• Aggressive behavior
• Withdrawal 
• Post-traumatic stress disorder
• Poor concentration
• Poor performance at school
• Depression
• Phobias
• Eating disorders
• Precocious sexual behavior with peers

Sources: Thought Nova, Journal of Child Sexual Abuse, Clinical Psychology Review, Patient

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Conclusion

Incest, even when consensual, is not a victimless crime. It’s impossible to talk about incest without tearing up over the epidemic of child sexual abuse because most of the sexual abuse of children is incestual. 

While the prevalence of incest varies around the world, the numbers often rely on victims who are willing to self-report and perpetrators who were caught in the act. Because of this, incest may be far more common than we know.

The risk of incestual child abuse increases when parents fight or are distant from their children. Abused or neglected children can inflict sexual abuse on their siblings. Parents, aunts, uncles, and grandparents also commonly commit incest on children for a variety of reasons. 

First and second-cousin marriages are a common form of consensual incest throughout the world but greatly increase the risk of hereditary diseases and other negative health factors for their children. 

Ultimately, incest is linked to abuse and unhealthy sexual attitudes in most of the people who engage in it. More often than not, it is nonconsensual. Whatever the cause of incest may be in any given scenario, it is always preferable to sleep with someone outside your own family.