OCD

Aetiology

Setotonin

The predominant hypothesis about OCD pathophysiology, originating from treatment studies and pharmacologic manipulation of the serotonin system, implicates an abnormal regulation of brain serotonergic function (Murphy et al., 1989). Pharmacologic challenge studies and neuro-imaging studies have resulted in compelling evidence supporting neurobiological abnormalities in patients suffering from OCD (Flament and Bisserbe, 1997).

The realisation that clomipramine is effective in the treatment of OCD led to the hypothesis that serotonin was important in OCD. It is now known that potent serotonin reuptake inhibition is a pre-requisite for effective OCD treatment (Hollander et al., 1992). The efficacy of the clomipramine and the SSRI antidepressants, which have potent serotonin reuptake inhibiting properties, is in sharp contrast to the lack of efficacy, in several studies of antidepressants such as desipramine, clorgyline and phenelzine which have no inhibiting effect on serotonin (Goodman et al., 1990; Insel et al., 1983; Leonard et al., 1989; Vallejo et al., 1992; Zohar and Insel, 1987). This has differentiated OCD from the depression spectrum disorders.

Other evidence of serotonin involvement in OCD is from studies which show in creased CSF 5-HIAA which subsequently decreases after successful treatment (Thoren, et al., 1980). Other studies showed an increase in OCD symptoms after m-CPP (Zohar, et al., 1988; Hollander et al., 1992). Once the patient had been treated with an SRI the effect of the behavioural and neuroendocrine effects of m-CPP were normalised.

New Ideas Affecting OCD Treatment

One of the most exciting new approaches in the treatment of OCD is based on the identification of a paediatric subtype of OCD. Parallel lines of research on Sydenham’s chorea (the neurologic variant of rheumatic fever) and on paediatric OCD and Tourette’s syndrome led to the development of a subgroup of children who developed their OCD and/or tic disorder after group A beta-haemolytic streptococcal pharyngitis (Swedo, 1994; Swedo et al., 1989).

OCD can lead to severe impairment in function. The new treatment possibilities create several interesting research opportunities and our knowledge and ability to treat OCD will continue to improve as more data in collected.