There are many risk factors for developing alcohol dependence, with both environmental and biological influences playing a role. One of the environmental risk factors that can be very powerful is past experience with trauma. Though it is unclear how trauma affects the decision-making process involved with alcohol dependence, research has shown that trauma dramatically increases the risk for developing alcohol dependence. A study published by Carolyn E. Sartor and colleagues examines the relationship between posttraumatic stress disorder and alcohol dependence in women. The researchers sought to distinguish PTSD-specific influences on alcohol dependence from the contribution of co-occurring psychiatric conditions and from the influences more generally associated with trauma. The researchers conducted telephone interviews with 3,768 female twins, assessing trauma histories and DSM-IV lifetime diagnoses, including PTSD and alcohol dependence. The data was used to categorize the participants as no trauma (43.7 percent), trauma without PTSD (52.6 percent), or trauma with PTSD (3.7 percent). The data was analyzed with Cox proportional hazards regression, using trauma\/PTSD status to predict alcohol dependence. The researchers first adjusted only for ethnicity and parental problem drinking. The second adjustment included analysis of conduct disorder, major depressive disorder, regular smoking and cannabis use. The results of the analysis indicated that before accounting for psychiatric covariates, there were elevated rates of alcohol dependence in both trauma-exposed groups. Those with PTSD were at a significantly greater risk than those not diagnosed with PTSD. Though this distinction was not consistent once psychiatric covariates were included in the analysis, the trauma-exposed groups both continued to show elevated risk of developing alcohol dependence compared with those who had no history of trauma. The higher risk of alcohol dependence in women with a history of trauma is not fully explained by psychiatric conditions that tend to co-occur with alcohol dependence and exposure to trauma. The researchers believe that the results showing a greater likelihood of developing alcohol dependence in the subset of trauma-exposed individuals who develop PTSD may reflect higher levels of distress or higher rates of psychopathology that occur with traumas that result in PTSD rather than influences related directly to PTSD. While the results indicate that PTSD greatly influences the likelihood that a woman who had experienced trauma will develop alcohol dependence, it is unclear whether the risk is directly associated with PTSD or the trauma that led to the PTSD. Further research may be required to examine the types and severity of trauma that increases risk of PTSD and therefore increases risk of alcohol dependence.