Tourette syndrome and obsessive compulsive disorder: Compulsivity along the continuum

The strong genetic link between obsessive compulsive disorder (OCD) and Tourette syndrome (TS) raises the possibility that obsessions and compulsions may comprise an alternative phenotypic expression of tics. Both of these disorders are characterised by repetitive behaviours (RB) involving recurrent thoughts and/or actions, often linked to dangerous or taboo themes, which present fairly early in life and tend to follow a chronic waxing and waning course. Over time many studies have attempted to disentangle the clinical profiles of these disorders. This article explores the key differences revealed by research over the last few decades, examining the types of RB expressed, patients' accompanying phenomenological experience (e.g. cognitive and sensory correlates), the proposed neural bases for each condition, and common interventions. Attempts to distinguish between OCD and TS based on the specific types of RB have often met with limitations. However, existing literature pertaining to the phenomenological experience of OCD and TS indicates that a number of factors may help differentiate these commonly associated conditions. Furthermore, differences in the psychological and physiological correlates of RB in TS and OCD are broadly in accordance with neuroimaging data. Study findings could offer insight into the predominance of TS diagnosis in males, age-related changes in diagnoses and the association between more context-dependent tic-like behaviours and OCD in patients with TS. Future studies should explore relationships between the cognitive, emotional and sensory aspects of RB and patients' demographical characteristics, neuropsychological test performance, and neural profiles.