**1. Introduction**

162 Epidemiology Insights

Weisz, J. R., Sandler, I. N., Durlak, J. A. & Anton, B. S. (2005). Promoting and protecting

*Psychologist*, Vol.60, 628-648, ISSN 0003-066X

youth mental health through evidence-based prevention and treatment. *American* 

Tics are the most frequent movement disorders during childhood; their highest prevalence occurs at scholar and adolescence-ages. Most tics are transient but some of them become chronic having educational, familial and social negative implications.

Moreover, some tics are related to disorders with significant impact, like attention-deficit hyperactivity disorder (ADHD), obsessive-compulsive (OCD) and affective disorders. Epidemiological studies are the initial approach to diagnose them and properly begin treatment.

In this chapter, we explained the clinical bases of tics, review the more representative epidemiological studies that assess the prevalence of tics and make a critical standpoint of these studies about epidemiology applicable to clinical practice.
