Here's a brief excerpt from Benjamin Beit-Hallahmi's chapter "Atheists: A Psychological Profile" in The Cambridge Companion to Atheism:
Who Are They? Demographics
In representative surveys of the U.S. population in the 1970s and 1980s, the unaffiliated were found to be younger, mostly male, with higher levels of education and income, more liberal, but also more unhappy and more alienated in terms of the larger society (Hadaway and Roof 1988; Feigelman, Gorman, and Varacalli 1992). According to 2004 Gallup data, based on 12,043 interviews, the 9 percent of Americans who say they do not identify with any religion whatsoever or who explicitly say they are atheist or agnostic tended to be politically liberal, Democrats, independents, younger, living in the West, students, and those who are living with someone without being married (Newport 2004).
In Australia, secularists are much better educated than the rest of the population, socially liberal, independent, self-assertive, and cosmopolitan. In Canada, census data and national surveys show that those reporting “no religion” are younger, more male than female, more urban than rural, as well as upwardly mobile (Beit-Hallahmi and Argyle 1997).
Being an atheist overwhelmingly means being male. Data from all cultures show women to be more religious than men (Beit-Hallahmi 2005b). Recent polling data from the United States show that the statement “there is a god” was endorsed by 72.5 percent of men and 86.8 percent of women. The statement “I don’t believe in any of these” was endorsed by 7.0 percent of men and only 1.3 percent of the women (Rice 2003).
Parents and the Making of Atheists
Findings regarding those who come from religious homes and then give up religion show that they have had more distant relations with their parents (Hunsberger 1980, 1983; Hunsberger and Brown 1984). Caplovitz and Sherrow (1977) found that the quality of relations with parents was a crucial variable, as well as a commitment to intellectualism. Hunsberger and Brown (1984) found that lesser emphasis placed on religion in home, especially by the mother, and self-reported intellectual orientation had a positive impact on rejecting the family’s religiosity as a young adult. Dudley (1987) found that alienation from religion in Seventh-Day Adventist adolescents was correlated (0.72) with the quality of their relationship with their parents and other authority figures. Alienation was tied to authoritarianism and harshness on the part of the parents. But parents may also have a more consonant effect on their children’s religiosity. Sherkat (1991), analyzing large-scale U.S. surveys in 1988, found that parents’ religious exogamy and lapses in practice led to their children’s apostasy. Thus, children may be following in their parents’ footsteps or acting out their parents’ unexpressed wishes.
Attachment theory (Kirkpatrick 2005) assumes that interpersonal styles in adults, the ways of dealing with attachment, separation, and loss in close personal relationships, stem directly from the mental models of oneself and others that were developed during infancy and childhood. Attachment styles can be characterized as secure, avoidant, or anxious/ambivalent. Secure adults find it relatively easy to get close to others. Avoidant adults are somewhat uncomfortable being close to others. Anxious/ambivalent adults find that others are reluctant to get as close as they would like. Kirkpatrick (2005) reports that in a study of 400adults in the United States, those having an avoidant attachment style were most likely to identify themselves as either atheist or agnostic.
Does losing a parent early in life lead one to atheism? Vetter and Green (1932–33) surveyed 350 members of the American Association for the Advancement of Atheism, 325 of whom were men. Among those who became atheists before age twenty, half lost one or both parents before that age. A large number in the group reported unhappy childhood and adolescence experiences. (The twenty-five women reported “traumatic experiences” with male ministers. We can only wonder about those today.) Vitz (1999) presents biographical information from the lives of more than fifty prominent atheists and theists as evidence for his theory that atheism is a reaction to losing one’s father.