High motivation and belief in a cause have been reported to be protective against posttraumatic stress disorder (PTSD), while below-average intellectual functioning and poor educational achievements have been reported to increase vulnerability to PTSD. The main goal of this study was to assess the effect of education, and intellectual and behavioral functioning on the risk for future PTSD. Data collected before exposure to trauma, on intellectual and behavioral functioning, and educational achievements of 901 male Israeli adolescents who had performed pre-induction screening tests by the Israeli Draft Board, and were later diagnosed with PTSD, were compared with a control group of adolescents who were not later diagnosed with PTSD. Future PTSD patients had significantly lower intelligence, fewer years of formal education and lower scores on a scale assessing motivation to serve in the military, in comparison with the control group, with effect sizes (ES) ranging from 0.14-0.34. In contrast, future PTSD patients scored significantly higher on a scale assessing social functioning, ES=0.13. However, when controlling for the differences in motivation to serve, all of these differences disappeared. In this cohort, although slightly below average intellectual functioning and formal education, and better social functioning, independently increased vulnerability to suffer from PTSD, these associations disappeared when the future PTSD patients' lower motivation to serve in the military was included in the analysis. This suggests that low motivation to serve in the military might increase vulnerability for PTSD.