Tics are common in childhood but transient in most cases. The estimated prevalence of
Tourette’s disorder ranges from 3 to 8 per 1,000 in school-age children. Males are more commonly affected than females, with the ratio varying from 2:1 to 4:1. A national survey in the United States estimated 3 per 1,000 for the prevalence of clinically identified cases.
The frequency of identified cases was lower among African Americans and Hispanic
Americans, which may be related to differences in access to care.
Onset of tics is typically between ages 4 and 6 years. Peak severity occurs between ages 10 and 12 years, with a decline in severity during adolescence. Many adults with tic disorders experience diminished symptoms. A small percentage of individuals will have persis- tently severe or worsening symptoms in adulthood.
Tic symptoms manifest similarly in all age groups and across the lifespan. Tics wax and wane in severity and change in affected muscle groups and vocalizations over time. As children get older, they begin to report their tics being associated with a premonitory urge—va somatic sensation that precedes the tic—and a feeling of tension reduction follow- ing the expression of the tic. Tics associated with a premonitory urge may be experienced as not completely ”involuntary” in that the urge and the tic can be resisted. An individual may also feel the need to perform a tic in a specific way or repeat it until he or she achieves the feeling that the tic has been done ”just right.”
The vulnerability toward developing co-occurring conditions changes as individuals pass through the age of risk for various co-occurring conditions. For example, prepubertal children with tic disorders are more likely to experience attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and separation anxiety disorder than are teenagers and adults, who are more likely to experience the new onset of major depressive disorder, substance use disorder, or bipolar disorder.
Tem peramental. Tics are worsened by anxiety, excitement, and exhaustion and are better during calm, focused activities. Individuals may have fewer tics when engaged in schoolwork or tasks at work than when relaxing at home after school or in the evening. Stressful/exciting events (e.g., taking a test, participating in exciting activities) often make tics worse.
Environmental. Observing a gesture or sound in another person may result in an indi- vidual with a tic disorder making a similar gesture or sound, which may be incorrectly perceived by others as purposeful. This can be a particular problem when the individual is interacting with authority figures (e.g., teachers, supervisors, police).
Genetic and physiological. Genetic and environmental factors inﬂuence tic symptom expression and severity. Important risk alleles for Tourette’s disorder and rare genetic variants in families with tic disorders have been identified. Obstetrical complications,
Older paternal age, lower birth weight, and maternal smoking during pregnancy are as- sociated with worse tic severity.
Tic disorders do not appear to vary in clinical characteristics, course, or etiology by race, ethnicity, and culture. However, race, ethnicity, and culture may impact how tic disorders are perceived and managed in the family and community, as well as inﬂuencing patterns of help seeking, and choices of treatment.
Males are more commonly affected than females, but there are no gender differences in the kinds of tics, age at onset, or course. Women with persistent tic disorders may be more likely to experience anxiety and depression.
Functional Consequences of Tic Disorders