Although in the literature there is a large number of studies concerning the association between PTSD and physical comorbidities, epidemiological data are scarce, particularly in Italy. In addition, previous investigations focused on specific types of comorbidities and there is a lack of a comprehensive assessment of all the ICD categories. The present study is the first one investigating all the ICD medical comorbid conditions and the related gender differences in Italian PTSD patients. Findings showed that specific comorbidities represent a serious issue in PTSD with metabolic, circulatory and musculoskeletal systems/connective tissue diseases being the most frequent ones. While gender is not associated with symptom presentation, it seems to play a key role in specific comorbidities, with males presenting a higher frequency of metabolic/circulatory diseases and females showing more frequently neoplastic conditions.
Comparisons with previous studies related to the prevalence of comorbidities in PTSD patients are difficult due to the different way of coding the pathologies: many studies focused on specific diseases (e.g., diabetes ) instead of all the ICD9CM categories that were used in this paper. Furthermore, existing findings about comorbidities prevalence showed a large degree of heterogeneity, partly due to the differences in study populations (e.g., veterans or general population). As mentioned before, in this study the percentage of positive patients was used as an approximation of the prevalence and this matter makes any comparison more inaccurate. Keeping in mind all these recommendations for the interpretation of the findings, the Italian group of PTSD patients showed interesting similarities and differences with other studies. In this group of subjects, findings showed a percentage of 17.86% of patients with metabolic syndrome, a proportion that was comparable to the study of Ching-En and colleagues  in Taiwan, where 12.91% of the PTSD population showed a comorbidity with this disease. Other studies reported much higher values of prevalence: according to the review of Rosenbaum and colleagues , the estimation of the metabolic syndrome prevalence in PTSD patients was 38.7% (CI: 32.1%-45.6%) and another study on Bosnian post-war PTSD showed a value of 48.3% .
The development of metabolic syndrome may be due to the stress of the trauma which acts through the neuropeptide Y and glucocorticoid systems . Alternatively, it may be hypothesized that PTSD patients develop metabolic problems as a consequence of dysfunctional strategies used to cope with stress such as alcohol drinking .
Such a heterogeneity concerns other health-related problems as well. For example, diseases of the circulatory system were reported by 20.24% of the Italian PTSD patients, by 42% of a group of refugees psychiatric patients in Asian populations , by 5.35% in Taiwanese general population (both for hypertension) , or by 15% in Australian Vietnam war veterans . An explanation why the stress of the trauma is associated with diseases of the circulatory system may be related to an overactive sympathetic nervous system, haemodynamic reactivity, impaired sympathetic and cardiovagal baroreflex sensitivity, and increased inflammation that could contribute to cardiovascular risk .
Lastly, with regard to cancer, it was detected in 8.33% (a generic neoplasm) of Italian PTSD patients but was reported by 42.2% (basal cell carcinoma or squamous cell carcinoma) of subjects enrolled in the study of McLeay and colleagues . Again, the comparison between the comorbidities assessed in the Italian PTSD group and the prevalence among the general population, showed the same problem of data comparability, due to the lack of health information coded through the ICD9CM categories. In this study, 17.86% of the PTSD patients had a metabolic syndrome diagnosis, a percentage which was near to the estimation provided by Miccoli and colleagues for the Italian population . However, in our study, this disease was more common in women than in men (18% vs. 15%), the opposite of the findings concerning the Italian group of PTSD patients, where the proportion of subjects with metabolic syndrome was 5.56% for women and 27.08% for men. Looking at the ICD9CM code related to neoplasm, this study showed a quite high percentage of subjects affected by this disease (8.33%), with a significant gender difference, since 16.67% of females were diagnosed for neoplasms, compared to 2.08% of males. Data concerning Italian general population did not confirm this difference: according to the AIRTUM Working Group , the prevalence in Italy during 2014 was 4.56%, with no substantial difference between females (4.90%) and males (4.20%). The quite high prevalence of neoplasms in PTSD patients may be attributed to a number of immune changes including increased circulating inflammatory markers, increased reactivity to antigen skin tests, lower natural killer cell activity, and lower total T lymphocyte counts .
Much more difficult was the comparison with the Italian general population for the diseases of the circulatory system. Giampaoli and colleagues  estimated that in Italy during the period 2008-2012, 1.6% of men and 0.6% of women suffered from acute myocardial infarction, 52.5% of men and 37.8% of women were diagnosed for hypertension and 0.7% (both sexes) experienced cerebrovascular accidents. In this study, a percentage of 20.24% PTSD patients reported a disease of the circulatory system, with a significant gender difference (29.16% males vs. 8.33% females) that is confirmed by the literature and by the general population health status.
In conclusion, this study conducted on a group of Italian PTSD patients confirmed the literature findings on the association between this disorder and medical conditions. Overall, comorbidities showed a high frequency and a higher prevalence than in the Italian general population. Results suggested also that gender may play an important role in developing comorbidities when subjects are affected by PTSD, as suggested by other studies . Our study suggests that assessment and treatment of PTSD patients during clinical and forensic practice should take into account such comorbidities. Due to the limitations of the study design and the difficulty comparing these findings with national and international data, this research brings out the need for deepening this topic in the Italian population.