Obsessive-compulsive disorder (OCD), the fourth most common psychiatric disorder,<sup>72 Karno M., Golding J.M. Obsessive compulsive disorder Psychiatric Disorders in America: The Epidemiologic Catchment Area Study New York: Free Press (1991).  204-209

Cliccare qui per andare alla sezione Riferimenti</sup> is a chronic and heterogeneous condition characterized by sudden, recurrent upsetting cognitions that intrude into consciousness (obsessions), and rule governed acts that the person feels driven to perform (compulsions). Recognizable descriptions of OCD symptomatology are found in the fifteenth-century religious documents on demonology and seventeenth-century observations on abnormally intense religious scruples. Equivalent descriptions of obsessions were reported in the eighteenth and nineteenth centuries by authors, such as Hartley (“fixed and recurrent ideas” in 1774); Esquirol (“reasoning monomanias or partial deliria” in 1838); Krafft-Ebing (“obsessive representation” in 1867); Griesinger (“ruminative sickness” in 1868), and Legrand du Saule (“touching madness” in 1875).<sup>1 Alarcon R.R., Libb W.J., Boll T.J. Neuropsychological testing in obsessive–compulsive disorder: A clinical review J Neuropsychiatry Clin Neurosci 1994 ;  6 : 217-228

Cliccare qui per andare alla sezione Riferimenti</sup>

In the modern era, substantial advances have been made in the recognition and treatment of OCD. Nonetheless, the mechanisms by which treatments confer their beneficial effects as well as the cause and pathophysiology of OCD remain incompletely understood.

As described in other sections of this issues, the hypothesis of basal ganglia involvement in OCD stems, in part, from the description of obsessive-compulsive symptoms (OCS) or OCD in several neurologic disorders known to affect basal ganglia structures, such as postencephalitic parkinsonism<sup>62 Jelliffe S.E. Psychopathology of forced movements in oculogyric crises Nerv Ment Dis 1932 ;  151 : 550-552

Cliccare qui per andare alla sezione Riferimenti</sup> (see elsewhere in this issue), Sydenham's chorea<sup>118 Rapport J. The biology of obsessions and compulsions Sci Am 1989 ;  260 : 82-89

Cliccare qui per andare alla sezione Riferimenti</sup> (see elsewhere), Huntington's disease<sup>33 Cummings J.L., Cunningham K. Obsessive–compulsive disorder in Huntington's disease Biol Psychiatry 1992 ;  31 : 263-270  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> (see elsewhere), Tourette's syndrome<sup>111 Pauls D.L., Towbin K.E., Leckman J.F. , e al. Gilles de la Tourette's syndrome and obsessive–compulsive disorder evidence supporting a genetic relationship Arch Gen Psychiatry 1986 ;  43 : 1180-1182

Cliccare qui per andare alla sezione Riferimenti</sup> (see elsewhere), and lesions in the neostriatum<sup>150 Weilburg J., Mesulam M.M., Weintraub S. , e al. Focal striatal abnormalities in a patient with obsessive–compulsive disorder Arch Neurol 1989 ;  46 : 233-235

Cliccare qui per andare alla sezione Riferimenti</sup> and globus pallidus.<sup>76 Laplane D., Levasseur M., Pillon B. , e al. Obsessive-compulsive and other behavioral changes with bilateral basal ganglia lesions: A neuropsychological, magnetic resonance imaging and positron emission tomography study Brain 1989 ;  112 : 699-725 .

Cliccare qui per andare alla sezione Riferimenti</sup> Findings from neuroimaging research (see elsewhere) provide additional evidence supporting a role for corticostriatal pathways in the pathophysiology of OCD.

In this article, we provide a review of the epidemiology and phenomenology of OCD, as well as an overview of relevant neurobiologic research and a summary of effective treatment strategies.