If you have that one friend whose jokes tend to be inappropriate and excessive he or she may be suffering from a severe condition called witzelsucht.

Witzelsucht is a mental condition where an individual has a tendency to tell inappropriate jokes or puns, excessively. More often than not, it is a result of a focal lesion, which is an infected tumor or injury involving the orbitofrontal cortical or paramedian thalamic regions of the brain.

The orbitofrontal cortical region is located in the frontal lobe of the brain and is responsible for cognitive processing and decision-making. The thalamus region is located between the cerebral cortex and midbrain. It has many functions including sending sensory and motor signals to the cerebral cortex as well as managing an individual's consciousness, sleep and alertness.

The frontal lobe, which is located in the right side of the brain, is where an individual's personality lies and any damage to this region can result in severe mood shifts, tastes and interest. While an individual who has an injury to the left side of the brain becomes depressed and angry, an injury to the right side of the brain increases euphoria and one tends to become cheerful.

This new cheerful personality trait is commonly perceived as tactless and can ruin social interactions. A study conducted by Taiwanese researchers reported a 56-year-old man, suffered a stroke in his orbitofrontal region and developed witzelsucht and hypersexuality. He would make inappropriate jokes and sexual puns excessively that doctors frequently interrupted him in order to conduct tests on him.

However, people who suffer from witzelsucht are unable to respond to jokes of others. Many times they would sit through jokes or comedies with no response.

Currently the most common way to treat this condition is through behavioral therapy. Doctors will attempt to explain to the individual that the jokes are not humorous for others. If the problem persists, the physician can prescribe mood stabilizers in attempts to return the individual to his or her former self.