Usually, other warning signs of sickness cause patients or their families to seek help, but sometimes, laughter is a medical symptom that deserves attention. Here's an example: In 2007, a 3-year-old girl in New York began having seizures that were quite unusual -- she grimaced and laughed during her episodes. Doctors discovered that she had a rare form of epilepsy that was causing the involuntary laughter, and they performed surgery to remove a benign tumor that was growing in the girl's brain. The operation cured her of her laughing fits [source: Chang].
Surgeons and neurologists have helped people with brain tumors or cysts that cause uncontrollable and embarrassing fits of laughter. Removing these growths eliminates pressure on the parts of the brain that trigger involuntary laughter. An acute stroke can also cause pathological laughter [source: Kim].
Then there's Angelman syndrome and Tourette syndrome, both of which carry laughter as a symptom. Angelman syndrome (AS) is a rare chromosomal disorder that affects the nervous system. People with this condition usually cannot speak and display "a happy, excitable demeanor with frequent smiling and laughter" [source: NIH]. They laugh frequently due to heightened stimulation of the parts of the brain that control happiness. Tourette syndrome (TS) is a neurobiological disorder that causes a combination of tics and involuntary vocal outbursts. People with TS usually don't need treatment unless their tics interrupt daily activities like work or school. Medication and psychotherapy can help patients minimize their symptoms.
Laughter can also be a symptom of drug abuse or chemical addiction. In both of these illnesses, a malfunction occurs in the way the nervous system transmits signals -- even those that trigger laughter. Dementia and anxiety can also cause abnormal laughter.
To learn more about laughter as a medical symptom, explore the links on the next page.