Individual differences in human sexual desire can be attributed to genetic variations, argue researchers at the Hebrew University of Jerusalem. The findings are believed to have an impact on people's understanding of their own sexuality as well as to how sexual disorders may come to be treated in the future.

The study represents the combined efforts of researchers directed by Prof. Richard P. Ebstein, of Herzog Hospital and the head of the Scheinfeld Center for Human Genetics in the Social Sciences of the Psychology Department at the Hebrew University, and a research group headed by Prof. Robert H. Belmaker of the Psychiatry Division of Ben Gurion University of the Negev.

Scientists studied how common variations in the sequence of DNA impact sexual desire, arousal and orgasm intensity and lead to differences and diversity of the human sexual phenotype. Researchers say that the implications of these findings are far-reaching and represent a revolutionary change in the way society, and especially psychology, may come to regard this central element of human behavior. This progress in understanding the biological basis of human sexuality provides a new way of viewing variations in sexual norms, without passing moral judgment.

Until now psychologists considered that most significant variations in the expression of human sexuality are the result of learned behavior or psychological problems. However, recent advances in molecular genetic studies of human behavior and personality, imaging studies of sexual arousal and performance, and neuroendocrinological investigations suggest that individual variations in many aspects of human sexuality are in fact genetically determined.

Israeli investigators examined the DNA of 148 healthy male and female Israeli university students and compared the results with questionnaires asking for the students' self-descriptions of their sexual desire, arousal and orgasm intensity. The results showed a correlation between variants in the D4 receptor gene and the students' self-reports on sexuality. The D4 receptor is responsible for producing the dopamine receptor protein (DRD4), dopamine being a neurotransmitter linked to pleasure.

Interestingly, some forms of variants in this gene were shown to have a depressing effect on sexual desire, arousal and orgasm intensity, while other common variant had the opposite effect - an increase in the sexual desire score. The latter is believed to be a relatively new mutation, and it is estimated that it appeared in Homo sapiens "only" 50,000 years ago at the time of humankind's great exodus from Africa. Approximately 30% of many populations carry the heightened arousal mutations, while around 60% carry the depressant mutation.

The investigators predict that as a result of their work, and other advances in neurosciences focusing on sexual behavior, a conceptual change will result, in which new therapeutic pathways will be developed for treatment of sexual dysfunctions based on a rational pharmacogenetic strategy. Additionally, the investigators note that many variations such as "low sexual desire" may be quite normal and not necessarily a product of dysfunction.

It is possible, therefore, say the researchers, that sexual "problems" will thus be rerouted to a great extent from the classical psychological couch into the realm of 21st century, genomics-based medicine.