Obsessive-compulsive disorder (OCD) is a mental illness that causes repeated unwanted thoughts or sensations (obsessions) or the urge to do something over and over again (compulsions). Some people can have both obsessions and compulsions.
​
OCD isn’t about habits like biting your nails or thinking negative thoughts. An obsessive thought might be that certain numbers or colours are “good” or “bad.” A compelling habit might be to wash your hands seven times after touching something that could be dirty. Although you may not want to think or do these things, you feel powerless to stop. Health care providers do not know the exact cause of OCD.

​

Factors that may play a role include head injury, infections, and abnormal function in certain areas of the brain. Genes (family history) seem to play a strong role.