Scientists still do not really know what causes obsessive-compulsive disorder (OCD) but there is some evidence that it runs in families. Most studies into this have looked at an overall diagnosis of OCD but OCD is made up of a number of different symptoms and it could be that some symptoms are more likely to be inherited than others. Previous research has shown that symmetry/ordering and hoarding both have a stronger family link than other symptoms of OCD but little research has been done into the relationship between family factors and OCD tendencies in people not being treated for the condition. This could be useful as people who haven't been treated for OCD are less likely to be affected by other mental-health problems or treatments which could affect the results of a study. There is also the theory that OCD symptoms are just one end of a spectrum of behaviour that affects everyone to a certain degree so that information gained from a non-clinical sample could be applied to those with the condition. Researchers from Barcelona and the Institute of Psychiatry, King's College London, studied 184 female undergraduates and their parents assessing their OCD tendencies using questionnaires. They found that there was a link between both parents' OCD tendencies and those of their daughters with the link being stronger from mother to daughter. Ordering and hoarding were particularly strongly linked between mothers and daughters and ordering scores in mothers predicted other symptoms in their daughters such as washing and checking.
Taberner, Joan ... [et al] - Are obsessive-compulsive symptom dimensions familial in nonclinical individuals Depression and Anxiety October 2009, 26(10), 902-908