Military veterans are one of the groups most likely to develop symptoms of post-traumatic stress disorder (PTSD). Substantial numbers of veterans affected by PTSD also have diagnosable symptoms of substance use disorder (substance abuse and\/or substance addiction). In a study published in 2014 in the journal Mental Health and Substance Use, a team of American researchers assessed the level of unusually aggressive behavior in military veterans dealing with both PTSD and diagnosable substance problems. These researchers also identified those affected veterans most susceptible to participation in such behavior. PTSD and Military Service A person with post-traumatic stress disorder has life-impairing reactions to emotional trauma exposure that last for more than a month following that exposure, or only first arise a month or more after exposure. Common symptoms of the disorder include an involuntary reliving of traumatic experiences while awake or asleep, a powerful urge to avoid anything that serves as a reminder of a traumatic experience, a damaging increase in \u201cdown\u201d or negative emotions and moods and an unusual inability to shut off the heightened sense of alertness or jumpiness that characterizes the human \u201cfight-or-flight\u201d response. Two groups of military servicemen and servicewomen have particularly high chances of developing PTSD: people exposed to combat (or environments in which combat occurs) and people who experience some form of sexual assault or sexual harassment. The federal National Center for PTSD estimates that 11 percent to 20 percent of all veterans of Iraq and Afghanistan have diagnosable symptoms of post-traumatic stress disorder. Broadly speaking, this rate of PTSD development matches the rate for conflicts dating to the Vietnam era. Roughly 23 percent of all female veterans report experiencing some form of sexual assault while involved in military service. PTSD and Substance Problems Over 20 percent of all U.S. military veterans with PTSD also develop symptoms that qualify them for a substance use disorder diagnosis, the National Center for PTSD reports. Conversely, nearly one-third of all veterans seeking treatment for their substance problems have diagnosable cases of PTSD. Compared to people only affected by PTSD and people only affected by substance use disorder, people dealing with both of these illnesses have unusually high chances of experiencing issues such as severely strained personal and social relationships, an inability to maintain a fulfilling or stable daily routine and pain-centered physical ailments. This is true, in part, because the presence of substance abuse\/addiction can significantly worsen the impact of post-traumatic stress disorder. Link to Aggressive Behavior In the study published in Mental Health and Substance Use, researchers from the Medical University of South Carolina and the Veterans Administration used a project involving 97 U.S. military veterans to examine the rate of aggressive behavior in veterans simultaneously impacted by PTSD and substance use disorder. All of the study participants were in treatment for the two forms of illness. The researchers concluded that 39 percent of these participants had engaged in some form of aggressive behavior in the 30 days prior to the beginning of the study. They also concluded that fully 58 percent of study participants had engaged in some form of aggressive behavior throughout their lifetimes. The researchers characterized both the recent and lifetime rates of aggression as \u201chigh\u201d in comparison to the rates found in the general public. After completing a detailed analysis, the researchers concluded that several groups of military veterans affected by PTSD and substance problems have particularly prominent chances of displaying aggressive behavior in the recent past. These groups include those individuals with relatively severe forms of certain PTSD symptoms, those individuals who are relatively young, those individuals with the highest rates of combat exposure, those individuals with the highest rates of sexual assault exposure, those individuals who contemplate suicide and those individuals who often drink and use marijuana\/cannabis. The researchers also identified groups of veterans affected by PTSD and substance problems with the highest lifetime risks for aggressive behavior. These groups include those individuals with relatively severe forms of all PTSD symptoms, those individuals who are relatively young, those individuals most severely impacted by depression and those individuals most heavily impacted by significant stress after completing military service. The study\u2019s authors consider their findings to be preliminary, but also note the possible contribution of their work to the improvement of the identification and treatment of military veterans dealing with both post-traumatic stress disorder and diagnosable substance problems.