A tic is a brief, purposeless and often repetitive muscle movement or vocalization, such as eye blinking, throat clearing, or shoulder shrugging. When tics are persistent and difficult to control, the sufferer is often diagnosed with a tic disorder. Tic disorders are neurological conditions that usually emerge during childhood, but in some cases — often due to another medical condition — onset can occur in adulthood.

Most people with tic disorders report feeling a building-up of tension in a particular part of the body and must perform the tic in order to obtain relief — similar to having an overwhelming urge. So while the tic appears somewhat voluntary, it is also in a sense involuntary. Some experts call this phenomenon “semi-voluntary” or “unvoluntary.”

Tics may be classified as motor tics or phonic (or verbal) tics. Motor tics are brief, meaningless and jerky muscle movements, such as eye blinking, arm or leg jerking, face grimacing, neck stretching, eyebrow raising, etc. Phonic tics are those that make a sound using the mouth/airway and/or voice. These might include sounds such as clicking, throat clearing, grunting, squealing, moaning, snorting, etc.

Tics may also be classified as simple or complex. Simple tics involve only one type of repetitive motor or phonic tic, while complex tics involve a cluster of movements or sounds and appear more coordinated. For example, this could be a repetitive tic that involves stretching the neck, blinking the eyes and clicking the tongue, either all at once or in particular order.

Tourette syndrome (TS) is one of the most well-known and potentially severe types of tic disorders. In order to be diagnosed with TS, a person must present with two or more motor tics and at least one phonic tic with symptoms lasting for at least one year. Symptoms also must begin before 18 years of age. Over 85 percent of people with TS have co-morbid conditions, such as obsessive compulsive disorder (OCD), attention deficit hyperactivity disorder (ADHD), depression or anxiety.

People with OCD may exhibit symptoms that are typically associated with tic disorders. In fact, tic-related OCD is considered a subgroup of OCD, distinguishable from non-tic-related OCD by the content and type of obsessions and compulsions. Those with tic-related OCD tend to have more intrusive thoughts and experience more hoarding and counting rituals than those with non-tic-related OCD.

Lesser known forms of tic behaviors that sometimes emerge in people with TS, OCD or autism include echolalia (repeating another person’s words), echopraxia (repeating or imitating another person’s actions), palilalia (repeating one’s own words), lexilalia (repeating words out loud after reading them) or klazomania (compulsive shouting).

Coprolalia (saying aloud socially objectionable words or phrases) is a highly publicized symptom of Tourette syndrome; however, only about 10% of TS patients exhibit coprolalia. A similar version of this is copraxia (performing obscene or inappropriate gestures).

Many patients with tic disorders notice an increase in symptoms during times of relaxation or boredom and a decrease during moments of intense concentration. Neurologist and author Oliver Sacks, for example, wrote of a surgeon with severe Tourette syndrome whose tics remitted almost completely while performing surgery.

Example: Tommy was diagnosed with Tourette syndrome after experiencing a year of stressful and unwanted tics of eye blinking, head shaking and tongue clicking.