Allostasis refers to the psychobiological regulatory process that brings about stability through change of state consequential to stress. Allostatic regulation describes the recovery and the maintenance of internal balance and viability amidst changing circumstances consequential to stress. It encompasses the Type 1 allostatic load that reflects the utilization by the organism of the range of behavioral and physiological functions that direct the adaptive function of regulating homeostatic systems in response to challenges (i.e. stress response) to develop temporary or permanent adaptation skills by means of self-preservation. Type 1 allostatic responses translate the organism aims at surviving the perturbation in the best condition possible and at normalizing the normal life cycle. By contrast, the Type 2 allostatic responses reflect a load to the organism that is excessive, sustained, or continued, and drives allostasis chronically and that precludes effective escape from the stress. The Type 1 and Type 2 allostatic response dichotomy provides a theoretical model for future research and treatment of PTSD and complex PTSD.

The purpose of evidence-based research in medicine is to elucidate the best available evidence in response to a stated clinical problem (e.g. is complementary medicine effective with patients with PTSD?). Following the scientific process of evidence-based research and the generation of the consensus statement (Fig. 2), the information is implemented and evaluated by the clinician. Effectiveness and utilities data are estimated (e.g. Markov model) to aid the final clinical decision-making process (74).

Evidence-based research in medicine follows the 5-step scientific process that includes stating the research question, which in evidence-based research consists of the PIC/PO question (What is the population being examined, e.g. patients with PTSD? What are the interventions being looked at, e.g. conventional treatment versus complementary medicine? Are the interventions being compared or are predictions being drawn, i.e. meta-analysis versus meta-regression approach? What is the outcome of interest, e.g. activities of daily living?). The second step involves methodology, including the sampling of the research literature, and the tools for the critical analysis of the reports. The third step refers to design which usually fall under the acronym CONSORT (i.e. consolidated standards of clinical trials). The fourth step is concerned with the analysis of the data gathered in the evidence-based research process. This commonly entails meta-analytical and meta-regression techniques, as well as individual patient data analysis (e.g. number needed to treat, NNT). Depending upon the tools utilized to evaluate the scientific literature, scores about the completeness and quality of research methodology, design and statistical handling of the findings are generated (SESTA, systematic evaluation of the statistical analysis). These values are analyzed by acceptable sampling statistical protocols to establish whether or not the sample of research reports studied by means of the evidence-based process was statistically acceptable to produce reliable inferences. The last step is a cumulative synthesis, which summarizes the process and the findings. The consensus statement reflects the best available evidence with respect to the stated PIC/PO question. The process is applied to the performance of systematic reviews, which are all-encompassing of the available literature. Best case studies in evidence-based research entail a random performance of the process of evidence-based research with a random sample of the available literature.