( CNN ) -- After actress Mackenzie Phillips spoke about her sexual relationship with her musician father , online and telephone calls to an anti-sexual assault hot line surged . Mackenzie Phillips told Larry King that incest survivors are `` incredibly underrepresented . '' Her interviews in the past few weeks brought a spotlight to an uncomfortable topic . Incest , a common but highly stigmatized form of sexual abuse , often leaves the victim ashamed , isolated and unable to tell others what 's happening , because the perpetrator is someone related to him or her , mental health experts said . `` For any survivor of sexual trauma , it 's challenging , and it takes a lot of courage to come forward , '' said Jennifer Wilson , director of the National Sexual Assault hot line . `` With incest survivors , it 's particularly difficult , because not only is there social stigma pressuring them to stay quiet , but also there 's pressure that 's within the family to stay quiet . '' The Rape , Abuse & Incest National Network , which calls itself the nation 's largest anti-sexual assault organization , said it had seen an 83 percent increase in activity on its online hot line and a 26 percent increase on its telephone hot line after Phillips ' interview with Oprah Winfrey aired last week . `` Unfortunately , it 's something we hear everyday in our hot line , so to have somebody speak aloud about it was empowering to a lot of victims and survivors who went through similar situations , '' Wilson said . Phillips spoke about the taboo nature of incest in her interview with CNN 's Larry King . `` There 's very little in this world that is taboo today , but this subject is still , like , shove it under the carpet , sweep it away , protect the abuser , deny the reality . ... You 're just on your own , '' the former child star said . This makes it one of the most under-reported and least discussed crimes , experts said . A U.S. Bureau of Justice Statistics report found that of the 60,000 sexual assault cases reported in 12 states in 2000 , about a quarter were perpetrated by family members . About half of the sexual assault cases with victims younger than 11 involved family members . At times , a victim may feel unable to tell other family members what 's happening . And if he or she tells a relative , that family member may have `` a knee-jerk reaction , '' refusing to believe it . Relatives may try to protect the offender in order to keep the family together or to avoid the shame and stigma , Wilson said . This takes a devastating toll on a victim . `` Their sexual selves are damaged . Their emotional selves are damaged , because 'who do I trust ? ' `` said Debra Laino , a sex therapist and counselor. `` 'My father did this . My mother did this . Who can I trust if I ca n't trust my family ? ' `` Sometimes the reluctance to report the crime comes from the victim , because he or she does n't want to see the family member in jail . Although Phillips called the sexual relationship with her famed father , John Phillips , `` wrong , '' she said , `` I do n't want bad things to happen to him , but I also do n't want bad things to happen to me as a result of this . And I was convinced to let it lie . '' Her father , a co-founder of the Mamas & the Papas , died in 2001 . Father- or stepfather-daughter incest is the most common form , although it also occurs between mother and child , according to the National Center for Victims of Crime . A sexual assault victim could suffer physical effects of the crime such as sexually transmitted infections , genital trauma and urinary tract infections . They could also experience many mental health effects : social withdrawal , isolation , post-traumatic stress disorder and regressive behavior such as bedwetting and thumb sucking . Some become hypersexual and engage in destructive behaviors , experts said . Humans `` have an instinct for avoiding incest or inbreeding , '' said Debra Lieberman , an assistant professor of psychology at the University of Miami ( Florida ) who researches incest . But alcohol , drugs and mental illness may disrupt that instinct . `` Under the heavy influence of cocaine or heroin or whatever else you 're taking , your mental boundaries are skewed , essentially , '' Laino said . The offender 's sexual frustrations could also contribute to inappropriate actions . `` It also depends on his other mating opportunities , '' Lieberman said . `` What is the quality of his current relationship with the female 's mother ? Is she around ? What is the ability for the guy to attract other mates ? '' The perpetrator , frustrated by the absence of suitable sexual partners , may turn to whomever is around -- even if it 's kin . Recovery from incest can occur , but it often takes years . A victim of incest has to understand that it 's not his or her fault and get professional help , Wilson said . `` It does n't make you broken , '' Phillips said . `` It does n't make it so that you ca n't go on and be -- once you deal with honestly and realistically what you 've been through , it does n't mean that you ca n't be counted on or you ca n't be well enough to be a part of the world . ''
Actress said she had sexual relationship with her father for years . Experts : Incest is one of the most under-reported and least discussed crimes . Comment: