Susan Brinkmann, in an article by that title (Women of Grace, August 18, 2008), describes how Fr. Jeremy Davies, 73, a priest of the Westminster diocese of the Catholic Church of England and a practicing exorcist, declared that promiscuity, whether heterosexual or homosexual, and New Age practices such as Reiki, can lead to demonic possession. There are a lot of different "gateway drugs" that lead to demonic oppression or possession, and it's best to be aware of them. There are two equal and opposite dangers: to be ignorant of the unseen presence of the demonic world, and to be overly curious and interested in that world.
[Hat tip to Dr. Mary Healy]