I was convinced that my body was full of cancer.

One night after playing basketball, I was showering when I felt a hard knot on the back of my knee. I pretended it was normal, just something from playing ball. I’d always had bad knees.

But I could already feel the panic bubbling in the pit of my stomach. I tried to push the thoughts from my mind. I turned on the TV. I thought about whatever work was due that week. But the thoughts wouldn’t go away. Instead, they got louder.

"Cancer." "Cancer." "Cancer."

That’s when I made the real mistake. I went to Google and typed in something along the lines of "lump on back of knee."

The results were conclusive. I had Non-Hodgkin’s lymphoma. I was going to die, and I was terrified. I remember sitting on the edge of my bed, still in a towel, literally shuddering as my mind raced to all the worst possible outcomes.

Sounds kind of absurd, right? Silly? Irrational? I agree. I felt the same way. But still, there was a nagging voice in the forefront of my mind. "What if?"

That was the worst thing. For all the rational internal dialogue, my mind always clung to that simple possibility of "What if?"

Because Non-Hodgkin’s lymphoma is a cancer of the lymph nodes, I became obsessed with my lymph nodes — something I’d never paid any attention to before in my life.

I found them all, but it was the ones on my neck, just below my jaw, that I particularly fixated on. I felt them so hard and so often that my neck was bruised.

I called in sick to work to lay on the couch trying to decide if my lymph nodes were swollen. I was at war with my own rationality, torn between how ridiculous the whole thing was and that unrelenting voice saying, "What if?"

I was engaged to be married, but was so distant and distracted that my fiancee thought I was breaking up with her. Cancer was all I could think about. I was consumed by a crippling, completely irrational fear.

When I finally told my fiancee what was happening, I broke down, relieved to finally say out loud what had been raging in my head for months. As a nurse, she convinced me to go to the doctor.

Turns out I had bursitis, which the doctor could handle, and Obsessive-Compulsive Disorder (OCD), which required a therapist.

Turns out I’d been dealing with situations like this off and on for as long as I could remember.

That was 10 years ago. Today, thanks to 30 daily milligrams of Celexa, my OCD is manageable. But it’s always there.

It might have helped, back when I thought I had cancer, to know just how common OCD is and the ways it affects the lives of millions of people around the world. People like David Adam, author of "The Man Who Couldn’t Stop: OCD and the True Story of a Life Lost in Thought." Adam, a British science writer and editor, recently answered some questions about his book and his own personal struggles with OCD:

Q: How do you think OCD is viewed within pop culture and among "average" people who are at least passingly familiar with the term?

A: I think it is viewed as a harmless behavioral quirk. Most people have a habit or mental tick and they assume it is the same.

Q: Why does OCD serve as punchline in movies and TV shows?

A: Partly because it’s a mental disorder that it’s seen as OK to laugh about. It’s not serious like schizophrenia and it’s more visual than anxiety and depression. There is a slapstick element to the physical checks and rituals — the man who, however many times he does something, never gets it right.

Q: You wrote "The Man Who Couldn’t Stop" because you have and continue to suffer from OCD. Was it difficult to remove yourself from the disorder in order to write about it, or did having personal experience with it provide helpful insights?

A: I decided to write the book because most writing out there already was divided into two camps: the clinical, written by doctors or scientists, which could be a bit detached, and the classic memoir written by someone still really suffering, which can be difficult to apply to one’s own experience. I thought that my experience of both science and the condition offered a way to bridge the two.

Q: OCD is defined by rather absurd yet unrelenting thoughts, so to verbalize it to someone who’s never been through it is to make it almost sound silly. How do you explain OCD to someone who thinks having OCD means being a "neat freak" or being a compulsive hand-washer? 

A: I simply ask them if they have ever had a really odd thought, like the urge to jump in front of an arriving train. And then I say OCD is like that, but the thought doesn’t ever leave.

Q: Have TV shows like "Hoarders" and "My Strange Obsession" helped to normalize and explain OCD, or just increased its freak factor, for lack of a better term?

A: I haven’t seen those specific shows. It’s hard to generalize about media coverage as some is good and some is awful. I think it’s OK to focus on the bizarre features of OCD — that, after all, is part of the diagnosis, that we recognize the thoughts as weird and silly — but it has to be done with compassion.

Q: Can you talk a little about your compulsion and why and how it started?

A: I have an irrational fear of HIV infection. My logical mind knows that I cannot catch HIV from, say, brushing against a doorknob with a small scratch on my hand, but the OCD tells me that I might and that I should check to make sure I haven’t. It started when I was 19, I think related to the way HIV was presented in the 1980s. It’s actually a very common form of OCD.

Q: Your book is part memoir, part research text. Was there a particular case that you found that helped you better understand the devastating impact OCD can have on people’s lives?

A: I think the most telling was the Ethiopian girl who ate a mud wall of her house, which I open the book with. I cannot think of a clearer demonstration of how OCD can force people to behave in a totally irrational way.

Q: You write about calling the AIDS hotline as part of fueling your obsession; my bane was Google, which opened new possibilities for diseases and panic I hadn’t even considered. Is the Internet friend or foe to OCD sufferers?

A: Like all media, it’s both. It helps people realize they are not alone and make contact, seek information, etc. But it’s also the perfect way to seek reassurance, ask questions anonymously and indulge fears, which consolidate the OCD and interfere with treatment.

Q: I live in the American South, where religion is the backbone of life and social interaction. What kind of impact can religious faith — or fear of things like hell and damnation — have as a trigger for OCD?

A: Religious belief is a common outlet for OCD. Very religious people can find themselves obsessed that they cannot stop thinking about sin, or that they have impure thoughts. Many religions stress the need for purity of thought, and that thought is the equivalent of action. Unfortunately those demands and patterns of thinking can encourage OCD.

Q: You write about medications and how they’ve helped you.

A: I think the evidence suggests that medication can help most people to feel better. It doesn’t help everybody but then nothing does. And for most people, it helps to also have a course of cognitive behavioral therapy as well.

Q: How are you now in terms of your OCD?

A: I tell people I have good and bad days now, and that is much better than only having bad days! I think the book has helped, because I am now open about my OCD and that makes it easier to manage, as I don’t have to hide it.

Contact Brett Buckner at brettbuckner@ymail.com.