Tourette syndrome is found among all social, racial and ethnic groups and has been reported in all parts of the world; it is three to four times more frequent among males than among females. The tics of Tourette syndrome begin in childhood and tend to remit or subside with maturity; thus, a diagnosis may no longer be warranted for many adults, and observed prevalence rates are higher among children than adults. As children pass through adolescence, about one-quarter become tic-free, almost one-half see their tics diminish to a minimal or mild level, and less than one-quarter have persistent tics. Only 5 to 14% of adults experience worse tics in adulthood than in childhood.

Up to 1% of the overall population experiences tic disorders, including chronic tics and transient tics of childhood. Chronic tics affect 5% of children, and transient tics affect up to 20%. Prevalence rates in special education populations are higher.

The reported prevalence of TS varies "according to the source, age, and sex of the sample; the ascertainment procedures; and diagnostic system", with a range reported between .4% and 3.8% for children ages 5 to 18. Robertson (2011) says that 1% of school-age children have Tourette's. According to Lombroso and Scahill (2008), the emerging consensus is that .1 to 1% of children have Tourette's, with several studies supporting a tighter range of .6 to .8%. Bloch and Leckman (2009) and Swain (2007) report a range of prevalence in children of .4 to .6%, Knight et al. (2012) estimate .77% in children, and Du et al. (2010) report that 1 to 3% of "Western" school-age children have Tourette's.

Singer (2011) states the prevalence of TS in the overall population at any time is .1% for impairing cases and .6% for all cases, while Bloch and colleagues (2011) state the overall prevalence as between .3 and 1%. Robertson (2011) also suggests that the rate of Tourette's in the general population is 1%. Using year 2000 census data, a prevalence range of .1 to 1% yields an estimate of 53,000–530,000 school-age children with Tourette's in the US, and a prevalence estimate of .1% means that in 2001 about 553,000 people in the UK age 5 or older would have Tourette's.

Tourette syndrome was once thought to be rare: in 1972, the US National Institutes of Health (NIH) believed there were fewer than 100 cases in the United States, and a 1973 registry reported only 485 cases worldwide. However, multiple studies published since 2000 have consistently demonstrated that the prevalence is much higher than previously thought. Discrepancies across current and prior prevalence estimates come from several factors: ascertainment bias in earlier samples drawn from clinically referred cases, assessment methods that may fail to detect milder cases, and differences in diagnostic criteria and thresholds. There were few broad-based community studies published before 2000 and until the 1980s, most epidemiological studies of Tourette syndrome were based on individuals referred to tertiary care or specialty clinics. Individuals with mild symptoms may not seek treatment and physicians may not confer an official diagnosis of TS on children out of concern for stigmatization; children with milder symptoms are unlikely to be referred to specialty clinics, so prevalence studies have an inherent bias towards more severe cases. Studies of Tourette syndrome are vulnerable to error because tics vary in intensity and expression, are often intermittent, and are not always recognized by clinicians, patients, family members, friends or teachers; approximately 20% of persons with Tourette syndrome do not recognize that they have tics. Newer studies—recognizing that tics may often be undiagnosed and hard to detect—use direct classroom observation and multiple informants (parent, teacher, and trained observers), and therefore record more cases than older studies relying on referrals. As the diagnostic threshold and assessment methodology have moved towards recognition of milder cases, the result is an increase in estimated prevalence.

Tourette's is associated with several comorbid conditions, or co-occurring diagnoses, which are often the major source of impairment for an affected child. Most individuals with tics do not seek medical attention, so epidemiological studies of TS "reflect a strong ascertainment bias", but among those who do warrant medical attention, the majority have other conditions, and up to 50% have ADHD or OCD.

Coprolalia is a manifestation that may come from or may be a part of many different underlying causes. Most commonly, however, people seem to associate coprolalia with Tourette syndrome. When it comes to Tourette syndrome, the pathology of what causes this type of tic is not well pinpointed, but there are several correlations.

First of all, some research has pinpointed decreased grey matter thickness within the insula and sensorimotor cortex as the cause of some cases. Research notes that behavioral and functional brain imaging evidence indicates that the premonitory sensory phenomena (PSP) is associated with brain activity in the insular cortex, which is linked to interoceptive awareness. In the results of this research, it is noted that increased tic severity scores are associated with premonitory urges. Along with this, there is also evidence for the involvement of the insular cortex in the perception of urges. When conducting the research, the researchers of this report found that there was a relationship between grey matter thickness and PSP and that premonitory urges in Tourette syndrome are inversely associated with grey matter thickness in the sensorimotor and insular cortices. [30]

Another possibility when it comes to Tourette syndrome is genetics. In a study conducted in 2017, researchers found that there was a possible genetic and neurobiological relationship of the disinhibition phenotype in Tourette syndrome patients. However, it is noted that more research would be needed to determine a direct relationship. [31]

Coprolalia is not unique to tic disorders; it is also a rare symptom of other neurological disorders.[9][10] It may occur after injuries to the brain such as stroke[10] and encephalitis;[10][11] in other neurological conditions such as choreoacanthocytosis,[12] seizures,[13] and Lesch–Nyhan syndrome;[14] and rarely in persons with dementia or obsessive- compulsive disorder in the absence of tics.[10]

While the reason for choosing words that are commonly thought of as inappropriate is widely unknown, Doctor Timothy Jay suggests that it is caused by damage to the amygdala. The amygdala is a region of the brain that normally oversees emotions such as anger and aggression. Because of this, it is thought that the use of inappropriate words is a verbal manifestation of the inability to control aggression, including verbal aggression. [32]

Tourette syndrome is a spectrum disorder—its severity ranges over a spectrum from mild to severe. The majority of cases are mild and require no treatment. In these cases, the impact of symptoms on the individual may be mild, to the extent that casual observers might not know of their condition. The overall prognosis is positive, but a minority of children with Tourette syndrome have severe symptoms that persist into adulthood. A study of 46 subjects at 19 years of age found that the symptoms of 80% had minimum to mild impact on their overall functioning, and that the other 20% experienced at least a moderate impact on their overall functioning. The rare minority of severe cases can inhibit or prevent individuals from holding a job or having a fulfilling social life. In a follow-up study of thirty-one adults with Tourette's, all patients completed high school, 52% finished at least two years of college, and 71% were full-time employed or were pursuing higher education.

Regardless of symptom severity, individuals with Tourette's have a normal life span. Although the symptoms may be lifelong and chronic for some, the condition is not degenerative or life-threatening. Intelligence is normal in those with Tourette's, although there may be learning disabilities. Severity of tics early in life does not predict tic severity in later life, and prognosis is generally favorable, although there is no reliable means of predicting the outcome for a particular individual. The gene or genes associated with Tourette's have not been identified, and there is no potential "cure". A higher rate of migraines than the general population and sleep disturbances are reported.

Several studies have demonstrated that the condition in most children improves with maturity. Tics may be at their highest severity at the time that they are diagnosed, and often improve with understanding of the condition by individuals and their families and friends. The statistical age of highest tic severity is typically between eight and twelve, with most individuals experiencing steadily declining tic severity as they pass through adolescence. One study showed no correlation with tic severity and the onset of puberty, in contrast with the popular belief that tics increase at puberty. In many cases, a complete remission of tic symptoms occurs after adolescence. However, a study using videotape to record tics in adults found that, although tics diminished in comparison with childhood, and all measures of tic severity improved by adulthood, 90% of adults still had tics. Half of the adults who considered themselves tic-free still displayed evidence of tics.

Many people with TS may not realize they have tics; because tics are more commonly expressed in private, TS may go unrecognized or undetected. It is not uncommon for the parents of affected children to be unaware that they, too, may have had tics as children. Because Tourette's tends to subside with maturity, and because milder cases of Tourette's are now more likely to be recognized, the first realization that a parent had tics as a child may not come until their offspring is diagnosed. It is not uncommon for several members of a family to be diagnosed together, as parents bringing children to a physician for an evaluation of tics become aware that they, too, had tics as a child.

Children with Tourette's may suffer socially if their tics are viewed as "bizarre". If a child has disabling tics, or tics that interfere with social or academic functioning, supportive psychotherapy or school accommodations can be helpful. Because comorbid conditions (such as ADHD or OCD) can cause greater impact on overall functioning than tics, a thorough evaluation for comorbidity is called for when symptoms and impairment warrant.

A supportive environment and family generally gives those with Tourette's the skills to manage the disorder. People with Tourette's may learn to camouflage socially inappropriate tics or to channel the energy of their tics into a functional endeavor. Accomplished musicians, athletes, public speakers, and professionals from all walks of life are found among people with Tourette's. Outcomes in adulthood are associated more with the perceived significance of having severe tics as a child than with the actual severity of the tics. A person who was misunderstood, punished, or teased at home or at school will fare worse than children who enjoyed an understanding and supportive environment.

The exact cause of palilalia is unknown.

Palilalia also occurs in a variety of neurodegenerative disorders, occurring most commonly in Tourette syndrome, Alzheimer's disease, and progressive supranuclear palsy. Such degradation can occur in the substantia nigra where decreased dopamine production results in a loss of function. It can also occur in a variety of genetic disorders including Fragile X syndrome, Prader-Willi syndrome, Asperger's syndrome, autism, and the speaker has no difficulty initiating speech.

Palilalia (from the Greek πάλιν ("pálin") meaning "again" and λαλιά ("laliá") meaning "speech" or "to talk"), a complex tic, is a language disorder characterized by the involuntary repetition of syllables, words, or phrases. It has features resembling other complex tics such as echolalia or coprolalia, but, unlike other aphasias, palilalia is based upon contextually correct speech.

It was originally described by Alexandre-Achille Souques in a patient with stroke that resulted in left-side hemiplegia, although a condition described as auto-echolalia in 1899 by Édouard Brissaud may have been the same condition.

Copropraxia is a tic consisting of involuntarily performing obscene or forbidden gestures, or inappropriate touching. Copropraxia comes from the Greek "κόπρος" meaning "feces" and "πράξις" meaning "action". Copropraxia is a rare characteristic of Tourette syndrome.

Related terms are coprolalia, referring to involuntary usage of profane words, and coprographia, making vulgar writings or drawings.

Coprographia is involuntarily making vulgar writings or drawings. Coprographia comes from the Greek "κόπρος" meaning "feces" and "graphia" meaning to write.

Related terms are coprolalia, the involuntary usage of scatalogical words, and copropraxia, the involuntary performance of obscene gestures.

While carrier females are generally an asymptomatic condition, they do experience an increase in uric acid excretion, and some may develop symptoms of hyperuricemia, and suffer from gout in their later years. Testing in this context has no clinical consequence, but it may reveal the possibility of transmitting the trait to male children. Women may also require testing if a male child develops LNS. In this instance, a negative test means the son's disease is the result of a new mutation, and the risk in siblings is not increased.

Females who carry one copy of the defective gene are carriers with a 50% chance of passing the disease on to their sons. In order for a female to be affected, she would need to have two copies of the mutated gene, one of which would be inherited from her father. Males affected with LNS do not usually have children due to the debilitating effects of the disease. It is possible for a female to inherit an X chromosome from her unaffected father, who carries a new mutation of the HGPRT gene. Under these circumstances, a girl could be born with LNS, and though there are a few reports of this happening, it is very rare. The overwhelming majority of patients with LNS are male.

The prognosis for individuals with severe LNS is poor. Death is usually due to renal failure or complications from hypotonia, in the first or second decade of life. Less severe forms have better prognoses.