Shyness is often seen as a hindrance to people and their development. The cause of shyness is often disputed but it is found that fear is positively related to shyness, suggesting that fearful children are much more likely to develop being shy as opposed to children less fearful. Shyness can also be seen on a biological level as a result of an excess of cortisol. When cortisol is present in greater quantities it is known to suppress an individual's immune system, making them more susceptible to illness and disease. The genetics of shyness is a relatively small area of research that has been receiving an even smaller amount of attention, although papers on the biological bases of shyness date back to 1988. Some research has indicated that shyness and aggression are related—through long and short forms of the gene DRD4, though considerably more research on this is needed. Further, it has been suggested that shyness and social phobia (the distinction between the two is becoming ever more blurred) are related to obsessive-compulsive disorder. As with other studies of behavioral genetics, the study of shyness is complicated by the number of genes involved in, and the confusion in defining, the phenotype. Naming the phenotype – and translation of terms between genetics and psychology — also causes problems.