Tourette syndrome (TS or simply Tourette's) is a common neuropsychiatric disorder with onset in childhood, characterized by multiple motor tics and at least one vocal (phonic) tic. These tics characteristically wax and wane, can be suppressed temporarily, and are typically preceded by an unwanted urge or sensation in the affected muscles. Some common tics are eye blinking, coughing, throat clearing, sniffing, and facial movements. Tourette's does not adversely affect intelligence or life expectancy. Tourette's is defined as part of a spectrum of tic disorders, which includes provisional, transient and persistent (chronic) tics. While the exact cause is unknown, it is believed to involve a combination of genetic and environmental factors. There are no specific tests for diagnosing Tourette's; it is not always correctly identified because most cases are mild and the severity of tics decreases for most children as they pass through adolescence. Extreme Tourette's in adulthood, though sensationalized in the media, is a rarity; tics are often unnoticed by casual observers.