recurrently been discussed as a third-party influence on the presence of dual diagnosis for PTSD and SUD. Avoidant coping styles have been shown to have a strong relationship to both PTSD and SUD individually, as well as presentation of concomitant PTSD and SUD together. Those with avoidant coping styles attempt to avoid interacting with or experiencing thoughts, feelings, or physical sensations reminiscent of the stressor in order to gain relief from the distress it causes. Substance use, for example, can allow a person to attempt to escape the distressing thoughts, feelings or physical sensations associated with the stressor the person is attempting to avoid experiencing. An avoidant coping style can therefore increase an individual's likelihood to seek means to avoid experiencing distressing sensations and increase likelihood of substance use overall. PTSD affects substance use disorders Individuals with comorbid PTSD and SUD tend to engage in more frequent and heavier substance use than individuals who have SUD alone. Additionally, research suggests that symptoms of PTSD can hinder abstaining from substance use. More generally, individuals with a dual diagnosis of PTSD and SUD have shown to be at increased risk meeting criteria for other psychiatric diagnosis in additional to PTSD and SUD when compared to those with SUD alone. Those with a dual diagnosis of PTSD and SUD have also been shown to seek treatment at higher rates than those who experience SUD alone. How substance use disorders affect PTSD The self medication hypothesis, as well as behavioral and emotional conditioning plays a role for people with dual diagnoses of PTSD and SUD. Symptoms of withdrawal, increased heart rate, sweating can mirror a human's natural physiological responses to fear, and can therefore trigger fear responses associated with that person's traumatic experience. Those with comorbid PTSD and SUD diagnoses may seek to avoid experiencing withdrawal to avoid experiencing these sensations that can act as fear inducing and triggering experiential catalysts. Additionally, individuals who chronically use substances as a form of self-medication for PTSD symptoms strengthen an automatic mental link between PTSD symptoms and the substance use itself via conditioning. Therefore, conditioned link between PTSD and substance use may trigger craving for substances when it arises, potentially increasing psychological dependence and complicating treatment outcomes for both diagnoses. Implicated brain systems Hippocampus and amygdala The hippocampus, which is responsible for encoding memory within the brain, is implicated in both PTSD and SUD. PTSD and SUD