officers kept issues to themselves while off duty. The study found that the social support between co-workers significantly buffered the relationship between work-related events and distress. Other studies have examined the social support systems of single mothers. One study by D'Ercole demonstrated that the effects of social support vary in both form and function and will have drastically different effects depending upon the individual. The study found that supportive relationships with friends and co-workers, rather than task-related support from family, was positively related to the mother's psychological well-being. D'Ercole hypothesizes that friends of a single parent offer a chance to socialize, match experiences, and be part of a network of peers. These types of exchanges may be more spontaneous and less obligatory than those between relatives. Additionally, co-workers can provide a community away from domestic life, relief from family demands, a source of recognition, and feelings of competence. D'Ercole also found an interesting statistical interaction whereby social support from co-workers decreased the experience of stress only in lower income individuals. The author hypothesizes that single women who earn more money are more likely to hold more demanding jobs which require more formal and less dependent relationships. Additionally, those women who earn higher incomes are more likely to be in positions of power, where relationships are more competitive than supportive. Many studies have been dedicated specifically to understanding the effects of social support in individuals with post traumatic stress disorder (PTSD). In a study by Haden et al., when victims of severe trauma perceived high levels of social support and engaged in interpersonal coping styles, they were less likely to develop severe PTSD when compared to those who perceived lower levels of social support. These results suggest that high levels of social support alleviate the strong positive association between level of injury and severity of PTSD, and thus serves as a powerful protective factor. In general, data shows that the support of family and friends has a positive influence on an individual's ability to cope with trauma. In fact, a meta-analysis by Brewin et al. found that social support was the strongest predictor, accounting for 40%, of variance in PTSD severity. However, perceived social support may be directly affected by the severity of the trauma. In some cases, support decreases with increases in trauma severity. College students have also been the target of various studies on the effects of social support