Tree thinking: a new paradigm for integrating comparative data in psychology.

Over the past 15 years, several important theoretical and methodological developments have emerged from evolutionary biology. These developments--collectively dubbed tree thinking--are now well known in evolutionary biology but have yet to be incorporated into mainstream psychology. Tree thinking has revolutionized evolutionary biology and has the potential to do the same for how comparative data are integrated into psychology. Tree thinking holds that explanations (or narratives) for adaptations must be based on an understanding of the adaptations' history (or chronicle) over evolutionary time. This tenet of tree thinking requires researchers to consider hitherto neglected patterns of data. The authors present the ideas and methods behind tree thinking, examining their implications for psychology.

Lifetime trauma exposure in veterans with military-related posttraumatic stress disorder: association with current symptomatology.

OBJECTIVE: This study examined whether trauma exposure before, during, and/or after military service contributed to current levels of post-traumatic stress disorder (PTSD) and adjustment. Further, we investigated whether trauma exposure before military service was mediated or moderated by military trauma in its effects on current PTSD and adjustment. METHOD: In this retrospective study, archival data from the medical records of 422 male veterans diagnosed with PTSD between December 2001 and July 2004 at a Veterans Administration Medical Center PTSD clinic were analyzed. Measures included the Clinician-Administered PTSD Scale interview as well as self-report measures assessing trauma history, health problems, and general psychopathology (including PTSD). RESULTS: Findings indicated that nonmilitary-related trauma was prevalent in this sample (90%). Regression analyses for PTSD symptom severity revealed that age, greater combat exposure, and a history of physical assault after military service were significantly associated with more severe PTSD symptoms. Childhood physical abuse, adult sexual trauma, and a history of being physically assaulted during military service were also significantly associated with PTSD symptom severity. Mediational analyses indicated that childhood trauma was associated with both adult trauma and increased symptomatology on various outcome measures. Moderational analyses indicated that adult trauma exposure moderated the effect of childhood trauma exposure on health complaints. CONCLUSIONS: Results suggest that several variables, including age, greater combat exposure, and premilitary and postmilitary traumas, are associated with increased PTSD symptomatology. This finding underscores the importance of conducting a thorough assessment of trauma when diagnosing PTSD.