What causes intrusive thoughts?

Intrusive thoughts may not have a cause. They can just happen randomly. Some thoughts wander into your brain. Then just as quickly, they exit, leaving no lasting impression.

Less commonly, intrusive thoughts are related to an underlying mental health condition, like obsessive-compulsive disorder (OCD) or post-traumatic stress disorder (PTSD). These thoughts could also be a symptom of another health issue, such as:

• brain injury
• dementia
• Parkinson’s disease

Signs that there might be an underlying cause include intrusive thoughts that:

• last longer than a brief moment
• continue to pop back into your head
• cause distress over time
• make you feel like you need to control your thoughts.

• These thoughts and images are unwanted and often unpleasant. The content can sometimes be aggressive or sexual, or you could suddenly think about a mistake or a worry.
• You might feel distressed when this happens, but having an intrusive thought once in a while is a typical part of li...