But the worry that "something bad will happen" is not an ephemeral, occasional threat for OCD sufferers. I avoided knives for years, because in their vicinity I feared I would lose control and stab my mother. Though at 13 I was still a child myself, I was terrified of molesting children, and could already see the newspaper headlines and the interminable jail sentence. My Catholic upbringing sent me to my knees—every 15 minutes, 60 times a day—praying that I wouldn't "hurt or kill anyone, please." Believing myself to be possessed by the devil, I began researching exorcisms. I wanted to tell my mother—but then how to explain I might kill her? To try to reverse the thoughts, I imagined turning the knife on myself instead.

Fred Penzel, Ph.D., is a founding member of the International Obsessive­Compulsive Disorder Foundation (IOCDF) and currently sits on its Science Advisory Board. He said that sexual and morbid obsessions crop up consistently in his conversations with patients.

"Most people don't understand OCD at all, to begin with. Secondly, most people tend to get too distracted by the content of the obsessions. The content is irrelevant," Penzel told me.

This content—thoughts of murder and pedophilia—can misdirect the treatment of OCD sufferers, pushing them toward the disciplinary system, rather than a mental health professional’s office. One woman fell into Penzel's care after her first therapist called the state's Child Protective Services after hearing the woman's fear of harming her child.

Another patient called Penzel from the maternity ward after she had given birth, explaining that hospital personnel had listened to her fears of harming her child and taken the infant away.

"She did say that [she had OCD]. They just heard 'harm my child,'" Penzel said.

Penzel said that the obsessive thoughts themselves are "mostly nonsense, and should never be taken literally."

In general, the violent and sexual obsessions that plague OCD patients actually repulse them.

Though I've never been sexually or romantically interested in women, as a child I was inundated with thoughts of performing cunnilingus on classmates. During basketball practice, I would think of fondling my classmates' breasts through our white cotton gym shirts and cross my arms in horror. I began to be convinced that I was gay, and that these undesired thoughts were just a part of growing up. This also works in the reverse: Penzel has written, "if [the patient] happens to be homosexual, they may obsess about the possibility that they might really be straight."

Obsessions fuel compulsions. When I had thoughts of hurting people I loved, I would kiss or press my tongue to the floor, recalling a ritual I’d seen in church. My loving God became a vengeful deity, one who would kill my family members before he would watch me disobey a compulsion. When I was 17 and living in Manhattan, this meant kissing dirty streets and subway floors. I would pretend to search for something under a seat on the train and peck the spotty ground with my lips. My OCD also involved thoughts of cleanliness, and this forced germ exposure seemed, to me, to serve as punishment for my thoughts.