The prevailing theory is that it is a combination of both. Although the psychological bases for OCD have been well noted in the research literature, recent DNA investigations have led to new areas of study. Researchers have discovered possible genetic markers for OCD on chromosomes 1, 3, 7, 6, and 15. The study of these markers, however, will involve years of investigation before anyone can state definitively the role of genes in the development of OCD.
In the combination of nature and nurture, the nature part has to do with our genetic and biological makeup. We all have certain genetic predispositions toward specific things. Our family history creates susceptibility for certain diseases or disorders in our genetic code. However, just because we may have a susceptibility does not mean that we will develop a disorder. That is where the nurture part of the combination occurs. We need to have the right stressors at the right times in order to “kick off” the predispositions that we have.
If OCD were influenced purely by our genetics, then every time one identical twin developed OCD, the other twin would have OCD as well. However, this does not happen. Although the prevalence of both twins having OCD if one twin has it is high (potentially 65, 85 percent), it is not 100 percent, therefore suggesting that nurture or other environmental triggers have some type of influence on the development of OCD.
For example, assume that there are identical twins with a genetic predisposition toward OCD. If they are adopted apart at birth, and one of them develops OCD, and the other does not, we can say that the environment played a major role because that is the only difference between the two twins, who are genetically identical.