Tics are rapid, irregular, involuntary movements (motor tics) or utterances (vocal tics) that interrupt normal voluntary motor activity. They are triggered by stress, anxiety, and fatigue but may also occur at rest; they can be suppressed by a voluntary effort, but tend to re-emerge with greater intensity once the effort is relaxed. Tics are often preceded by a feeling of inner tension. They may be transient or chronic.
Simple tics. Simple motor tics involve isolated movements, e. g., blinking, twitching of abdominal muscles, or shrugging of the shoulders. Simple vocal tics may involve moaning, grunting, hissing, clicking, shouting, throat clearing, sniffing, or coughing.