According to the DSM-IV-TR, TS is indicated when a person exhibits both multiple motor and one or more vocal tics (although these do not need to be concurrent) over the period of 1 year, with no more than 3 consecutive tic-free months. Previous versions of the DSM required that the disturbance must cause distress or impairment in the individual's normal functioning, but this requirement has been removed from the most recent version of the DSM, in recognition that not everyone with the diagnosis has distress or impairment to functioning. The onset must have been before the age of 18, and cannot be attributed to the use of a substance or another medical condition.
It is estimated that as many as 1 in 200 experience some form of TS. Males are affected 3 to 4 times more often than females. Some cases decrease in severity or cease entirely upon reaching adulthood.
As it is a spectrum disorder, the severity of the condition can range vastly. Those with mild cases are often highly functioning, so much so that others would not know of their condition. More severe cases (which are the minority) can inhibit or prevent the individual from engaging in common activities such as holding a job, having a fulfilling social life, or maintaining his/her basic needs.
Other commonly associated disorders are obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD)