A tic is a sudden, repetitive, nonrhythmic, stereotyped motor movement or vocalization involving discrete muscle groups. Tics can be invisible to the observer, such as abdominal tensing or toe crunching. Common motor and phonic tics are, respectively, eye blinking and throat clearing. Movements of other movement disorders (for example, chorea, dystonia, myoclonus) must be distinguished from tics. Other conditions, such as autism and stereotypic movement disorder, also include movements which may be confused with tics. Tics must also be distinguished from the compulsions of OCD and from seizure activity.
Obsessive–compulsive disorder (OCD) is a mental disorder characterized by intrusive thoughts that produce anxiety, by repetitive behaviors aimed at reducing anxiety, or by combinations of such thoughts (obsessions) and behaviors (compulsions). The symptoms of this anxiety disorder range from repetitive hand-washing and extensive hoarding to preoccupation with sexual, religious, or aggressive impulses. These symptoms can be alienating and time-consuming, and often cause severe emotional and economic loss. The acts of those who have OCD may appear paranoid and come across to others as psychotic. However, except in young children, OCD sufferers generally recognize their thoughts and subsequent actions as irrational, and they may become further distressed by this realization.