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What Causes Obsessive-Compulsive Disorder (OCD)?

Contributor Sabine Wilhelm, PhD
5 minute read
A woman sits on her sofa in front of a laptop, holding her head like she has a headache.

Obsessive-compulsive disorder (OCD) is a common mental health challenge. Sabine Wilhelm, PhD, a Mass General Brigham psychologist, answers common questions about what causes OCD, its triggers, and how it is treated. Dr. Wilhelm is the chief of psychology at Massachusetts General Hospital and the director of the Mass General Center for OCD and Related Disorders (CORD).

What is obsessive-compulsive disorder?

Obsessive-compulsive disorder is a psychiatric disorder. That means it affects a person’s mind, emotions, and/or behaviors.

“People with OCD suffer from obsessions and compulsions,” explains Dr. Wilhelm. “Obsessions are recurrent thoughts, but they can also be mental images. Typically, these obsessions cause a lot of anxiety, a lot of distress, so the person tries to get rid of them by engaging in a compulsion.”

Common obsessions include:

  • Fear of contamination (making something dirty or poisonous)

  • Fears of losing or forgetting something

  • Fears of having made a mistake

  • Concerns for symmetry or exactness

  • Disturbing, intrusive thoughts involving sex, religion, or violence

Common compulsions include:

  • Double-checking things, like locks, faucets, or switches, over and over

  • Frequent hand washing and/or cleaning

  • Repeating something again and again until it feels right

  • Replaying past conversations or events

  • Praying silently to prevent a feared event from happening

People with OCD may experience other obsessions and compulsions as well.

Risk factors for OCD

OCD can start in childhood or early adulthood. Most people who will have the disorder develop it by around age 25. It's usually a chronic disorder, and it can be managed with treatment.

We don't know for sure what causes OCD, but your family history, psychology, environment, and the way your body works could all play a role. Personality traits like perfectionism may put a person at risk of developing OCD. Stressful life events and psychological trauma may also play a role.

"We know that OCD runs in families, so if you already have a family member who has OCD, you are more likely to develop OCD yourself,” says Dr. Wilhelm.

Studies show that people with OCD have some biological traits in common. These include hyperactivity in specific of the brain and an imbalance in some of the brain’s chemical messengers (called neurotransmitters).

If you have OCD, or if you have a family member with OCD, please know that there’s hope.

Sabine Wilhelm, PhD
Mass General Brigham

How is OCD diagnosed?

Mental health care providers don’t diagnose OCD with brain screens or blood tests. Typically, they start with a diagnostic interview. In a diagnostic interview, providers ask patients a series of questions about their obsessions and compulsions. Afterward, they compare the patient’s results with specific criteria.

Many people with OCD have other disorders as well. These include, but aren’t limited to:

There are also some disorders that can look like OCD, such as body dysmorphic disorder.

Sometimes, OCD can be confused with personality disorders, such as obsessive-compulsive personality disorder (OCPD).

What is the difference between OCD and OCPD?

OCD and OCPD share some similarities. But they differ from each other in important ways.

The biggest difference between the two is that OCD includes distressing obsessions and compulsions, while OCPD does not. OCPD is a personality disorder that involves personality traits. It may include an extreme devotion to work, an inability to delegate tasks, or an excessive preoccupation with lists, rules, and order.

If you struggle with your mental health, it’s best to seek an official diagnosis if you can. An accurate diagnosis can help your provider find the right treatment options for you.

How is OCD treated?

There are two gold-standard treatments for OCD:

  1. Pharmacotherapy, or treatment using pharmaceutical drugs. Psychiatrists and other mental health care providers typically prescribe serotonin reuptake inhibitors (SSRIs) to patients with disorders like OCD. SSRIs can help with OCD by affecting the levels of serotonin in a patient’s brain. Serotonin helps regulate mood, which is why this may improve OCD symptoms.

  2. Cognitive behavior therapy (CBT). CBT is a kind of psychotherapy that helps patients notice and change disordered thought and behavior patterns.

    In CBT, patients first learn about their disorder. Then, they do exercises that teach them new ways to respond to their thoughts. They also learn to enter situations that they might be avoiding, and to prevent compulsions during triggering situations. It typically takes patients 16 to 20 sessions to complete CBT. The treatment is often helpful.

Sometimes, patients find that a combination of the two therapies works best. With the help of medication, some patients can get more out of CBT.

“If you have OCD, or if you have a family member with OCD, please know that there’s hope,” says Dr. Wilhelm. “We have effective treatments for people with OCD.”

Sabine Wilhelm, PhD