Homosexualty – The Medical Evidence

Notes from a lecture by Dr. Thomas Plante, Professor of Psychology Santa Clara University given in Professor Thomas Sheehan’s class “Radical Christianity” at Stanford University 

Thomas Plante is Ph.D. of Psychiatry and a Professor of Psychology at Santa Clara University .  He is also an Assoc Professor at the Stanford University Medical Center – Psychiatric Unit.  Dr. Plante has been a consultant to the Jesuits and Franciscans of the Catholic Church on sex abuse in the clergy

Index of questions and issues presented

    1. Nature / Nurture and Biophysical
    2. Is sexual orientation a choice?
    3. Is homosexuality a disorder?
    4. Can gays change their orientation?
    5. Do gays have committed relationships?
    6. Do gays make good parents?
    7. Psychological impact of civil unions or gay marriage.
    8. Sexual abuse in the Catholic clergy.
    9. Ethics and homosexuality and applying the RRICC model.
    10. Some Final Thoughts.
    11. Postscript.

Nature / Nurture and Biophysical  

Clinical evidence points to physiological factors, not lifestyle, as being the factors which dictate the design of an individual’s sexual orientation.   

  1. As a benchmark, gays represent approximately 5% of the general population.  
  2. In dizygotic (fraternal) twins, if one twin is gay there is a 20% chance that the other twin will be gay also.  But in monozygotic (identical) twins this probability rises to 50%.  This indicates that genetics is certainly a key factor in sexual orientation but genetics alone does not account for human sexual orientation.  
  3. During pregnancy, clinical studies show that abnormally high or low amounts of some hormones is a statistically significant factor in deciding human sexual orientation.  
  4. The feelings of love, caring and nurturing expressed by a gay couple are indistinguishable from heterosexual expressions of the same feelings.  In other words, one cannot deduce another’s sexual orientation based solely upon his/her description of these feelings about his/her partner.  

Is Sexual Orientation a Choice?  

The common mistake in assessing human sexuality is to assume that the two distinct orientations of heterosexuality and homosexuality are mutually exclusive.  That is to say a heterosexual has no homosexual inclination whatsoever and likewise that the homosexual has no heterosexual inclination.   

  1. There is no clinical evidence to support for this view.  Instead, studies show that there is a continuum of orientations between the two polar extremes.
    • There are bisexuals who are sexually attracted to both sexes even though they may prefer one sex to the other.
    • It is not uncommon for heterosexuals to have had a one-time homosexual experience as an experiment and the converse is true of homosexuals.
    • Neither homosexuals nor heterosexuals claim that they chose their orientation in a rational self-debate.  The orientation, homosexual or heterosexual, comes through a growing awareness of one’s natural inclination.  But clinical studies also show that normal human sexual orientation contains both homosexual and heterosexual components even when one orientation clearly dominates the other.
  1. Heterosexual prisoners will often exhibit homosexual behavior while incarcerated but, when returned to society, these same individuals will revert back to exclusive heterosexual behavior.

Is Homosexuality a disorder?  

Since 1973, the American Psychiatric Association, the American Psychological Association, the American Academy of Pediatrics and the National Association of Social Workers all agree that homosexuality is NOT a disorder or a mental illness.  Moreover as John McNeill stated in his book The Church and the Homosexual

When to such names as Freud and Krafft-Ebing, one adds those of Frank Beach, Harry Benjamin, Evelyn Hooker, Wardell Pomeroy, Alfred Kinsey, Robert Lindsay, Judd Marmor, Michael Shofield, Thomas Szasz and Ernest van den Haag, as well as the Wolfenden Committee, the most distinguished government group ever to undertake a study of the subject, it is obvious, to say the least, that the sickness theory does not command the universal acceptance in the scientific world that many assume it does.”  

Gay’s, as a group, do suffer more stress, depression and alienation than heterosexuals principally because society has yet to accept gays on equal terms with heterosexuals.  Being gay is not the problem, not being accepted by society is.  Consequently, gays can be divided into two clinical groups:  

  1. Egodystonic – I am gay and not ok with it
  2. Egosystonic – I am gay and that is not a problem for me.

*my own note: History shows that there has always some percentage of the general population that is gay. If humanity naturally consists of both heterosexual and homosexual orientations, then neither of them as component orientations of a “naturally” occurring population can be singled out as unnatural.  They each represent respectively only the majority and minority sexual orientations of the parent population.

Can Gay’s Change Orientation?

Of gays who have tried to change their orientation, Research shows:

  1. Only 4% of those who try are successful without continuing treatment
  1. Only 9% are successful but only when they remain in treatment.
  1. The remaining 87% revert back to homosexuality and repudiate the treatment.

Experts say that they would not attempt to change a gay person away from homosexual behavior in an attempt to replace it with heterosexual behavior.

Do Gays have Committed Relationships?

  1. Approximately 60% of gay men and women are in committed, long-term relationships.
  1. There is no evidence that homosexuals are any more promiscuous than heterosexuals.  As for marital (committed relationship) infidelity, it turns out that longevity has the greatest impact as a cause.  The reason is that marriages last longer because we as individuals have longer life spans than did our ancestors.  Therefore we are presented with longer term commitments accordingly.
  1. Since 1970, 46% of all first time heterosexual marriages end in divorce; 60% of second marriages end in divorce; and 70% of third marriages end in divorce.
  1. The remaining 53% of heterosexual marriages that have lasted are not all that happy for a variety of reasons.
  1. Interestingly, gay couples have less sexual dysfunction in their relationships than their heterosexual counterparts.  The reason seems to be that gay couples, being of the same sex, can better identify with their partners sexual needs than heterosexuals who have more difficulty making that identification in a partner of the opposite sex.
  2. See Note 1 at the bottom of this page.

Do Gays Make Good Parents?

Data show that children raised in homosexual families are no more likely to become homosexual than children raised in heterosexual families.  About 5% of the children in both types of families turn out to have a homosexual orientation.   (my note: this seems to confirm the assertion that sexual orientation is neither a learned behavior nor a consequence of environment but is instead innate in origin). 

Children, raised in a gay family, who are nurtured with love and affection are behaviorally indistinguishable from those raised in a similarly disposed heterosexual family environment.  

See Note 1 at the bottom of this page.

Psychological Impact of Civil/Gay Marriages

It is true that gays as a group experience a higher degree of angst, depression and propensity for suicidal behavior than the heterosexual population.  Psychiatrists believe that the reasons are more likely to be found in the lack of acceptance of gays by the general society than as a direct consequence of their homosexual orientation.  Not being accepted promotes secretiveness, a sense of insecurity and a reduced self-confidence and appreciation.

Sexual Abuse in the Catholic Clergy

Since Professor Plante is a consultant to certain dioceses of the Catholic Church he made the following observations:

  1. In nearly 81% of reported incidences of child abuse by Catholic clergy, the victims were young males between the ages of 11 to 14 .  The question that then arises is, “Are these abuses committed only by homosexual priests?”  While gay priests represent a higher percentage of all priests than gays do in the general population, the evidence suggests that that the incidents of abuse are a consequence of situational factors and accessibility (not unlike that which confronts the a prisoner as described above) rather than sexual orientation.
  1. Pedophilia is defined as pre-pubescent sex.  It is considered to be a sexual disorder and the occurrence of pedophilia in the gay population is no higher than in the heterosexual population.
  1. Consensual sex with a post-pubescent child, regardless of his/her age, may in some circumstances be considered statutory rape under the law but it is never pedophilia.
  1. Approximately 4% of priests are considered to be pedophiles but celibacy does not make pedophilia any more appealing than any other sexual interest. Among school teachers approximately 5% are pedophiles and in the general population it is a surprising 8%.
  1. Interestingly, 55% of the priest who were guilty of sexual abuse had only one victim.
  1. Some more facts:
    1. Nearly 30% of all Protestant Ministers are infidels
    2. Nearly 20% of all women and 15% of all men report that they were victims of sexual abuse as a child.

Ethics to Guide Society  

Plante has written a book entitled Do the Right Thing: Living Ethically in an Unethical World.  His main theme is that all human relations should be guided by the RRICC principle Respect, Responsibility, Integrity, Competence and Concern.   Because gays represent a historical percentage of the human population and considering the enormous weight of scientific evidence that homosexuality is neither a disorder nor a mental illness, applying the RRICC principle to gays as well is an ethical mandate.  

He ended his presentation with a quote from Micah in the Old Testament, “…and what does the Lord require of you but to do justice, love mercy and walk humbly with God.” 

Some Final Thoughts

Prior to Dr. Plante’s lecture, Professor Sheehan reviewed some of the more recent doctrinal changes made by the Catholic Church pertaining to human sexuality and practice.  The long-standing Catholic tradition holds that all human sexual activity must have a procreative purpose.  However several years ago, the Catholic Church conceded that the “rhythm method” is an acceptable birth control procedure.  Implicit in this approval then is the acknowledgment by the Church that sexual practices between consenting spouses are not necessarily restricted to procreative purpose alone.  The Church, moreover, acknowledges that the chief reason for marriage of a man and woman is not restricted just to procreation but more broadly includes the blending of two lives into a united whole to achieve a mutual interchange and sharing as its goal. 

While the Catholic Church and most all other Judeo-Christian religious institutions oppose gay relationships or any attempt to legitimize them with changes to civil laws,  the inability of a gay relationship to procreate can no longer be held as up as a justification for their opposition.  In addition, the latest medical research conclusions and the Church’s more enlightened view of spousal relationships together clearly erode arguments that support secular religion’s long-established homophobic position.  

The anti-homosexual position of Christian and Jewish religions is based upon a long standing tradition and a particular Biblical exegesis.  But, until the late 19th Century, the Christian world also had a long-standing tradition that endorsed black slavery and this position was also defended with its own particular Biblical exegesis.  Neither Christians nor Jews would today endorse black slavery for a variety of reasons and indeed no longer interpret scripture as supportive of it. So perhaps, this current societal controversy about the homosexual subset of our society, will be resolved with a more enlightened Biblical exegesis (see Homosexuality and the Bible ) and by applying the same civil rights laws developed to abolish the slavery and segregation of blacks.   Maybe we should begin by heeding the words of George Bernard Shaw who summed up the problem of Biblical exegesis thusly, “No man ever believes that the Bible means what it says. He is always convinced that it says what he means.”  


On October 12, 2006, the Oslo museum opened an exhibition, entitled “Against Nature?”, that is dedicated to the study of homosexuality in the animal kingdom. Homosexuality has been observed in nearly 1,500 different species and about one-third of these have been thoroughly studied and documented.  These studies show that some animals are consistently homosexual through our their lives and it is not uncommon to find homosexual partnerships that last for the lifetime of the animal couple.  Among penguins, for instance, as many as ten percent of the population form same-sexed pairs.  In some cases male/male pairs will even rear an egg from a female donor.   Homosexuality has been observed in most vertebrate groups, and also among insects, spiders, crustaceans, octopi and parasitic worms.  Since this behavior has been observed among so many species in the animal world, it cannot be explained as merely a lifestyle choice.  It is clearly a natural phenomena even though animals exhibiting homosexual behavior represent a minority in any particular animal population.


  1. Supreme Court of California filed an opinion on 5/15/08 regarding whether the state may describe the difference between opposite sex relationships differently from same sex relationships, i.e. is the difference in the official names “marriage” and ” domestic partnership” a violation of the California Constitution.  The court’s 4 to 3 decision was that the distinction was a violation.  In its decision, the court, inter alia, said, “Furthermore, in contrast to earlier times, our state now recognizes that an individual’s capacity to establish a loving and long-term committed relationship with another person and responsibly to care for and raise children does not depend upon the individual’s sexual orientation, and, more generally, that an individual’s sexual orientation — like a person’s race or gender — does not constitute a legitimate basis upon which to deny or withhold legal rights. We therefore conclude that in view of the substance and significance of the fundamental constitutional right to form a family relationship, the California Constitution properly must be interpreted to guarantee this basic civil right to all Californians, whether gay or heterosexual, and to same-sex couples as well as to opposite-sex   couples.”