Introduction: Post-traumatic stress disorder (PTSD) is frequently comorbid with other mental disorders, such as major depressive disorder (MDD), anxiety disorders (AD) and substance use disorders (SUD). Although causal pathways leading to such comorbidities have been widely documented in theory, only relatively few longitudinal population-based studies have attempted to assess the temporal relationships between these disorders. Consequently, the current study aimed to observe the sequence between of a lifetime or recent history of trauma, and PTSD, respectively, and the incidence of MDD, AD and SUD in a middle-aged population.
Methods: The participants of the current study were taken from the first three waves of a prospective cohort study, which was based on a random sample of the population of Lausanne (CoLaus|PsyCoLaus). Included participants (N = 3,447), who had participated in at least two consecutive assessments, were followed over a period of almost 10 years on average, and a semi- structured diagnostic interview (the Diagnostic Interview for Genetic Studies) allowed to elicit both their lifetime history and new incidence of major DSM-IV mental disorders and trauma. Odds ratios of developing either MDD, AD or SUD during the follow-up intervals, for the participants with a previous history of trauma or PTSD, were calculated using mixed-effects logistic regression models.
Results: We observed no statistically significant association between the history of trauma without subsequent PTSD development, or the history of PTSD, during the first wave, and the incidence of MDD, AD or SUD. The participants with both a positive history of trauma or PTSD and a new diagnosis of MDD, AD or SUD at follow-up developed these new disorders on average more than 25 years after the trauma or PTSD. Moreover, by the end of the follow-up period, none of the participants with PTSD that developed after the first wave developed any of these observed disorders, and only three of those who experienced trauma during this same interval developed new MDD.
Discussion/conclusion: After an initial delay, the low incidence of MDD, AD and SUD among those with a history of trauma or PTSD suggests that trauma and PTSD do not lead to the new onset of these other disorders in the longer-term. Therefore, assessing the risk of incident MDD, AD and SUD after this initial delay turned out to be not particularly clinically meaningful. Nevertheless, the low incidence of mental disorders among the participants who had experienced trauma or PTSD at the first wave, or subsequently during the follow-up interval, raises the question of the role of middle-age in the possible psychological consequences of trauma and PTSD.