There is a link between erectile dysfunction in heterosexual men and strong relationships between their partners and their male friends, U.S. researchers found. Benjamin Cornwell, a professor of sociology at Cornell University and Edward Laumann, a professor of sociology at the University of Chicago, describe the situation as \"partner betweenness\" -- in which a man\'s female partner has stronger relationships with his confidants than he does. In other words, the romantic partner comes between the man and his friends, the researchers say. \"Men who experience partner betweenness in their joint relationships are more likely to have trouble getting or maintaining an erection and are also more likely to experience difficulty achieving orgasm during sex,\" the researchers say in a statement. Cornwell and Laumann say partner betweenness undermines men\'s feelings of autonomy and privacy, which are central to traditional concepts of masculinity. The researchers used data from the National Social Life, Health and Aging Project, a comprehensive survey at the University of Chicago that included 3,005 people, ages 57-85. \"The results point to the importance of social network factors that are rarely considered in medical research -- network structure and the individual\'s position within it,\" Laumann said. The findings are published in the American Journal of Sociology.