Tic disorders are involuntary movements, vocalizations, or gestures that usually appear in childhood and can be classified based on frequency, length, age of onset, and manifestation. Transient tic disorders are short-lived and common, while chronic tic disorders last for more than a year and involve consistent repetitive behavior. Simple and complex tics are further classifications, with Tourette syndrome being the most severe form and possibly inherited genetically.
Tic disorders, which are characterized by involuntary movements, vocalizations, or gestures, usually appear in early childhood. For the most part, these tics typically go away with maturity. However, this isn’t always the case. In fact, those that have lasted 12 months or more are defined as chronic as outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM).
The DSM further defines the different types of tic disorders based on their frequency and length of expression. Other criteria used to classify tic disorders include age of onset, as well as the route of manifestation (ie, vocal or motor). Other criteria help isolate external factors that may contribute to tic disorders, such as emotional distress, physical trauma, or medications.
Transient tic disorders are by far the most common type, affecting up to 20% of children under the age of 18. As the name suggests, these types of tics are usually short-lived and subside over time without medical intervention. Transient tics can also manifest in a variety of ways. For example, transient phonic tic disorders may involve repetitive throat clearing or grunting, while transient motor tics may appear as constant blinking or coordinated finger movements. Transient tic disorders also commonly involve changing behaviors, often dismissing them as nervous habits.
A chronic tic disorder is defined as vocal or motor and lasts for more than a year, sometimes for several years. Unlike transient tics, the repetitive or involuntary behavior remains consistent throughout the duration of the disorder. Furthermore, chronic tic disorders commonly involve multiple behaviors of the same origin, but are never both motor and vocal.
There is also a distinction between simple tics and complex tics. For example, with simple motor tics, the involuntary movement is sudden and fleeting. In contrast, the movement made in complex motor tics seems more deliberate, even if it appears to be done consciously. Similarly, simple vocal tics involve making sounds or utterances at random, while complex vocal tics involve making actual words or phrases.
There are further classifications of simple and complex tic disorders. A vocal tic that includes suddenly blurting out obscenities is known as coprolalia, while the compulsion to repeat the same words over and over is called palilalia. Also, the “parroting” of words spoken by others is known as echolalia. Similarly, copropraxia is the term for making involuntary obscene gestures and echopraxia means imitating the gestures of others.
Tourette syndrome, also known as Tourette’s disorder, is the most severe form of tic disorder and is characterized by vocal and motor tics. The frequency and degree to which these tics take shape varies from individual to individual. There is some evidence to suggest that Tourette syndrome may be inherited genetically via bilineal inheritance, meaning it comes from both parents. Specifically, the researchers found a strong association between Tourette syndrome in children who also have fathers who exhibited childhood tics and mothers with a history of obsessive-compulsive behaviors.
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