The appearance of involuntary movements and sounds, known as tics, can be unsettling at any age. Tourette Syndrome (TS) is classified as a neurodevelopmental disorder, meaning it originates during the brain’s developmental period in childhood. While tics can suddenly appear in adulthood, this leads to a diagnosis fundamentally different from TS. A person experiencing new tics after age 18 is not diagnosed with TS, but rather with an “adult-onset” or “secondary” tic disorder, which requires investigation to identify the underlying cause.
The Age Requirement for a Tourette Syndrome Diagnosis
Tourette Syndrome is defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), which sets strict criteria for diagnosis. For a person to be diagnosed with TS, the first appearance of tics must have occurred before the age of 18 years. This age cutoff establishes TS as a disorder rooted in the developmental trajectory of the nervous system, distinguishing it from conditions acquired later in life.
The diagnosis also requires the presence of both multiple motor tics and at least one vocal tic, lasting for more than one year. Motor tics are sudden, brief, repetitive movements like eye blinking or head jerking. Vocal tics include sounds such as throat clearing, sniffing, or grunting.
When Tics Appear in Adulthood
When tics begin after age 18, the condition is categorized differently from TS, typically falling under an “Other Specified Tic Disorder” or “Tic Disorder, Unspecified.” This classification acknowledges that while the symptoms are physically indistinguishable from those seen in TS, the underlying cause is not the neurodevelopmental one required for a TS diagnosis. The primary medical task for adult-onset tics is ruling out other medical conditions or substances that could be causing the involuntary movements.
The tics, whether simple motor movements or complex vocalizations, may appear identical to those seen in a person with TS. Adult patients often report the same premonitory sensory urge—an unpleasant feeling or sensation that precedes the tic—that is commonly experienced by children with TS. However, since the age criterion has been surpassed, a clinician’s focus shifts to identifying a secondary or acquired cause.
Identifying the Underlying Causes of Secondary Tics
Tics that appear for the first time in adulthood are often symptomatic, meaning they are a manifestation of another medical issue or external factor. These secondary tic disorders require a different diagnostic approach than TS, focusing on identifying the specific trigger. Neurological damage is one potential cause; tics can follow events like a stroke, head trauma, or encephalitis, which affect the basal ganglia, the brain region associated with movement control.
Certain medications are also known to induce tics, particularly drugs that affect dopamine pathways, such as neuroleptics or stimulants. Tics can also be triggered by toxins or substances like cocaine abuse. In some cases, tics may be linked to an abnormal immune response following an infection, where antibodies mistakenly attack brain tissue.
A growing area of focus is on functional (or psychogenic) tic disorders, where the tics are not caused by neurological damage or a substance, but are related to psychological factors. These tics are often characterized by a rapid onset and can be linked to high levels of stress or anxiety. Recognizing that adult-onset tics are typically secondary to another cause is crucial for proper diagnosis and treatment.