What Is Obsessive-Compulsive Disorder (OCD)? What Are the Symptoms of OCD? How It Works


Patrick Carey


Michael A. Jenike, MD

Founder, OCD Institute at McLean Hospital Professor of Psychiatry, Harvard Medical School

Christopher Pittenger, MD, PhD

Director, Yale OCD Research Clinic Associate Professor of Psychiatry and in the Child Study Center, Yale School of Medicine

Because only OCD symptoms are
visible, it is widely misunderstood.

How OCD works for most people

Experts have come up with a bunch of different models for the way OCD works, and it varies from person to person. But here are the basics:

How OCD starts in people

This process can happen so quickly that it seems instantaneous. You might skip steps, or there may be extra steps in your case. But let’s go through each of them to find out more.

What’s a trigger?

Tons of things happen to us throughout the day. Certain things we barely even notice, while others make us feel happy, angry, sad, or however else. A trigger is one of those things in our environment (or sometimes in our own minds) that cause us to experience a certain thought or to feel a certain way. For instance, if you’re recovering from the grief of losing a loved one and you begin to feel sad when you hear their favorite song on the radio, that song is the trigger for your emotional state. 

This trigger doesn’t exactly cause the feeling, because there are other things contributing to this process (like the way you already felt, or the thoughts that might come in between the trigger and the feeling), but it’s still the trigger in that moment. It’s important to note that the trigger is not always easy to identify. Sometimes you might have a lot of unpleasant thoughts and feelings for seemingly no reason at all.

What are intrusive thoughts?

An intrusive thought is a thought, image, or urge that seems to pop up in your mind out of nowhere. Sometimes these thoughts seem completely random, and other times they might be traced back to some type of trigger. Intrusive thoughts sometimes seem really harmless. But other times they’re confusing, frightening, or even debilitating.

Here’s the big secret about OCD: these thoughts that bother people so intensely? Everyone has them.

Surveys of people without OCD reveal that they experience many of the same thoughts that completely derail people who have OCD. It’s hard to say whether or not people with OCD have these thoughts more often, but what we do know is that people with OCD react to these thoughts very differently. We’ll talk more about this in the next section, but let’s start with just a few examples of intrusive thoughts.

Intrusive Thoughts: Some Examples

  • I’m about to jump in front of the train
  • I could grab that cop’s gun and shoot myself
  • I could just kill myself
  • I should walk over and push that person
  • I should insult this person I don’t know
  • I could cut myself with this kitchen knife
  • I should jump off this bridge right now
  • I could push my friend off this bridge
  • I could kill my child right now
  • I’m going to punch my brother right now
  • I want to see my sister naked
  • I want to kiss my uncle
  • I could steal from this store right now
  • I could grab the money from that tip jar
  • I probably got HIV when I got a blood test
  • I’ve messed up everything in life
  • The person I’m dating isn’t right for me
  • There’s someone better for me
  • I’ll just tear my clothes off right now.
  • I’m more attracted to that person than to my partner
  • Life has no meaning
  • My niece is attractive
  • That child is attractive
  • I could be gay
  • I could be straight
  • I’m living a sinful life
  • I’m not a good person
  • Breathing is strange, I should stop breathing
  • Blinking is weird, I don’t like that people blink
  • Images of the above (you “see” it happening)
  • My family will be murdered
  • I could suddenly vomit in class
  • I should drive off the road right now.
  • I could run that person over right now.
  • Why not crash into that barrier?
  • I should just scream right now.
  • I’m going to tell my boss he’s an idiot right now.
  • I might dump this coffee on my boss’s head.

What’s a catastrophic assessment?

Everyone has had some of these intrusive thoughts, or similar ones: they pop into your head, and they’re strange or alarming. Most people might think for a few seconds about the unpleasant thought and then go on with their day. What’s different for people with obsessive-compulsive disorder is their inability to just let the thoughts pass by. Someone with OCD will have an intrusive thought, vastly overestimate its importance, and spiral into obsession.

Many people use intrusive thought and obsession interchangeably, but they’re not quite the same. As we saw above, everyone has intrusive thoughts. Like everyone else, people with OCD symptoms  experience mental illness and get different types of intrusive thoughts; only some of these become obsessions. This helps us understand why someone with OCD can be unbothered by most intrusive thoughts but completely derailed by others. Just because someone has OCD, does not mean they’re bothered by everything.

Let’s look at a common example: you’re driving along the highway, and you have the thought: I should drive off the road and smash into that barrier over there. Someone without OCD thinks: Wow, that was weird. Of course I don’t want to do that. And then they drive along and forget it ever happened. But someone with OCD might think: Oh god, not this again, I’m going to drive off the road, this means I want my life to be over, I don’t really want my life to be over, I need to make sure I don’t drive off the road, but maybe I do want to drive off the road?

The intrusive thought is the same for both, but the assessment of that thought is different. Unable to just move on, the person with OCD makes a catastrophic appraisal of the thought– that it’s important or dangerous and requires their attention– and so the obsession begins.

A man watching the train

What are obsessions?

In the above example, the person with obsessive-compulsive disorder feels an almost unbearably strong need to prove to themselves that they don’t actually want to drive off the road. Obsessions emerge from people’s strong feeling that they always need to be vigilant to different negative possibilities. In this case, it feels like the thought must mean that the person really does want to drive off the road, and so if they let their guard down their mind will take over and drive them off the road into the barrier.

Once an intrusive thought takes hold and starts becoming a source of distress, it has become an obsession. Obsessions are unwanted and repetitive thoughts, urges, and images that quickly spiral from an initial disturbing thought and usually lead to a lot of distress. While closely linked to intrusive thoughts both in theme and nature, obsessions only arrive after the initial thought has been assessed in a certain way. In a way, a central problem of OCD is the belief that every thought is meaningful.

Let’s look at another example of this process:

How Obsessions Get Started

Sam is babysitting his neighbor’s kids on a Friday night. As usual, the kids need to take a bath before bed. They’re young enough that Sam needs to help them.

The kids begin to get undressed for their bath.

Intrusive Thought
Suddenly Sam thinks: I could be sexually interested in these kids.

(Sam’s belief that every thought points to something real and important)

Oh no, could I really be sexually interested in young kids?
Am I the type of person who would be like that?
Could I really be a pedophile?
Are these kids in danger when I’m around?
How can I be sure that I’m not like that?
I need to make sure that I’m not really that kind of person.

We use the word “obsessed” in our culture to describe things we’re really interested in. He’s obsessed with her, she’s obsessed with checking her Instagram. But that’s not really how an obsession works for someone with OCD. They’re not interested in their obsession in a typical way. Rather, they tend to feel forced to think about it over and over. This makes sense, as an intrusive thought tends to become an obsession because it’s the most disturbing thing their minds could’ve thrown at them. And disturbing things can be hard to just accept or ignore.

Since obsessions are closely tied to the initial intrusive thought that brings them on, they can really spin out in any direction from any thought like the ones listed on the previous page. Just as there are infinitely many intrusive thoughts, there’s no limit to the obsessions that people experience. However, people with OCD aren’t really bothered by every thought that pops into their head. Instead, their obsessions usually emerge in response to intrusive thoughts within just a few themes at any given time.

What kind of distress can occur?

Emotional and physical pain in people with obsessive-compulsive disorder is by no means limited to the obsession stage. The pain might momentarily be soothed by compulsions, but it usually comes back even worse. And compulsions can create new types of distress, too. Distress is present throughout the obsessive-compulsive cycle, but we’re talking about it here because the main goal of compulsions is to get rid of the distress that obsessions cause.

Because people with OCD spend most of their day feeling like they have to make sure something bad won’t happen, a number of emotional symptoms can arise. Among the most common are trouble focusing, irritability, anger, frustration, jumpiness, guilt, shame, feelings of dread, and a sense of hopelessness.

People with OCD also experience a wide variety of unpleasant physical symptoms. Remember how you’ve felt right before taking an exam in school or getting test results back from a doctor? That feeling of being “amped up” is similar to what a person with OCD feels almost all the time. Their brain says “Time to be alert!” and their body responds by feeling constantly on edge. This can lead to exhaustion, an inability to sleep, digestive problems, muscle tension, dizziness, shortness of breath, and much more.

A sad girl sitting on a barrrier

Sometimes the emotional and physical symptoms work together in another kind of vicious circle– you begin to worry, notice you’re feeling worse, and then worry about feeling worse. Many people with OCD also develop symptoms of other psychiatric disorders, like depression and substance use, and then they have to manage multiple conditions at once. These tend to occur at significantly higher rates in people with OCD than in the general population, perhaps because of the amount of distress they experience.

People can also end up with any number of bodily symptoms from their compulsive behaviors. Someone with a hand washing compulsion can destroy the skin on their hands over time. Another person, refusing to eat because of an obsession about choking or contamination, may become extremely thin and develop medical complications.

People are typically aware, to varying degrees, of the irrationality of their thoughts and behaviors. Many people with OCD know that their thoughts aren’t real and that their behavior might seem strange to others, but they can’t stop despite these insights. But others do believe that their obsessions might come true, and that their compulsions are preventing this. It’s important not to be too quick to say, “Your thoughts don’t matter! You just need to learn to sit with them,” because many people do feel like their thoughts are important. Plus, many people have had the same symptoms for years. It takes time to feel alright about letting your guard down for a bit.

What’s a compulsion?

When their distress gets overwhelming, people with OCD will often engage in compulsions: repetitive activities aimed at getting rid of distress and regaining a sense of control. Compulsions develop over time, and sometimes they have nothing obvious in common with the content of the obsession. Anything that relieves distress is reinforcing, which means it’s going to seem more appealing the next time that distress shows up.

Eventually, a behavior can become almost automatic because it’s been done so many times; once this happens, and it’s hard to do anything else, it has become a compulsion. This helps us understand why certain “bizarre” compulsions seem to help people feel better short-term even though they have no logical connection to anything else: because this behavior helped the person feel better at one point in the past and developed into a compulsion via reinforcement.

Here are just a few examples of compulsions:

Compulsions: Some Examples


  • Excessive hand-washing
  • Constantly checking in with people to ensure their safety
  • Making sure things are neat and/or symmetrical
  • Checking locks, stoves, light switches repeatedly
  • Repeatedly counting or saying a word in your head
  • Checking trash repeatedly to make sure you aren’t throwing something valuable out
  • Looking for mistakes over and over when writing an essay or paying taxes
  • Looping back while driving to see if you’ve hit someone
  • Google Searching
  • Mentally replaying situations to make sure you remember them completely
  • Getting reassurance about things from other people
  • Visiting different doctors to see if you have an illness
  • Repeatedly apologizing to someone or asking if they’re okay
  • Keeping yourself away from kitchen knives because you get thoughts about stabbing someone
  • Staying away from kids because you get sexual thoughts about them
  • Refusing to visit public places because you’re afraid you’ll catch an illness
  • Avoiding crowded areas

Compulsions might provide a temporary sense of relief, but the anxiety quickly returns. You can never outrun your own mind, and anything designed to keep a certain thought out of your head is actually, perversely, guaranteed to make that thought pop up more often. This is the part in your psychology lecture when the professor says, “Whatever you do, don’t think of a big pink elephant.” By trying not to think of something, you’re already thinking about it, and the obsession tends to get stronger.

So compulsions only work for a bit, and the distressing thoughts start coming on more often as you try to get keep them away. This process begins to spiral, and the obsessive-compulsive cycle can start to take up the better part of your day. The more you perform compulsions, the less you trust yourself and the more you believe that you should be afraid of your own thoughts. And you never find out what would happen if you didn’t do a compulsion, and just let things happen.

Of course, many people with OCD don’t think about their experience in these terms, and simply feel like they have to do the compulsion for some unknown reason. Others are aware of what’s going on but still feel like the compulsion will either prevent something bad from happening, or help them feel better for a while. Many engage in avoidance of situations that might bring about their obsessions again; this avoidance, too, can become a compulsion.

A common misconception about obsessive-compulsive disorder is that people want to perform their compulsions. We see people washing their hands over and over, or refusing to leave their house, and assume that it’s part of their personality or a reflection of their interests. In reality, most people know that their compulsions don’t make any sense but are still unable to stop doing them. And even the people who don’t know this still aren’t doing the compulsions because they want to, but because they feel completely sure they have to.

In some cases, OCD symptoms can become so severe that people consider suicide. If you ever consider suicide, please call your local emergency number or go directly to a hospital. In the United States, you can also call the Suicide Hotline at 1-800-273-8255.

Related readings


How It Feels To Have OCD? Why OCD Thoughts Feel Real?

Every day, from the time I wake up to the time I finally go to bed, I’m overwhelmed by disturbing thoughts that I don’t want to have. They’re usually about things that matter a lot to me, and I’ve started doing specific things (sometimes over and over) just to make sure the thoughts won’t come true. I’ve also been avoiding situations that might bring the thoughts back. Why do I feel like this all the time?


How is OCD treated?

Without treatment, OCD can take over someone’s life. But improvements in therapy and medication over the past few decades have made OCD a highly treatable condition. It’s useful to understand what types of treatment have been most effective, so you can get back to living the life you want as soon as possible.


Common Types Of OCD

Sarah gets a lot of obsessive thoughts around kids, so she skips family events whenever her nephew will be there. Matt is so comfortable around kids that he works at a daycare center, but the idea of taking out the trash causes him so much anxiety that his wife always ends up doing it. Sarah avoids kids, and Matt avoids the trash. Do they have the same condition? Should they be treated similarly?