ACEs exposure could predict infectious diseases in adulthoods, through both direct and indirect negative effects on infectious diseases by positively affecting adult injection of drug use. Meanwhile, drug use injection also directly had positive effects on attacking by infectious diseases, but condom use was not associated with infectious diseases. Additionally, age, gender, ethnicity and education influenced infectious disease through altered behaviors of injecting drug use.
Our findings support the first hypothesis that injecting drug use was directly associated with infectious diseases, which was consistent with other studies [1, 36] A systematic evaluation of HIV and HCV prevalence among PWID in Afghanistan, Iran and Pakistan showed that PWID were at high risk of HIV and HCV transmission [37]. The Swiss HIV cohort study reported that IDU was associated with a higher risk of sexual transmission [38]. Nevertheless, studies have also shown that even in high-risk settings with years of IDU, 30–40% were not exposed to the HCV virus [39]. As these infectious diseases can be transmitted through blood, there was a high risk of contracting a blood-borne virus through injecting drug use, and the use of contaminated needles, syringes or drug injection equipment was the main cause of HIV and HCV infection [36]. Xishuangbanna region is traditionally an area of injecting drug use, with a high percentage of injecting drug use. The transmission of infection through unprotected sexual intercourse may sometimes be ignored in the context of infectious diseases caused by injecting drug use.
The study did not elucidate the relationship between sexual behavior and infectious diseases enough to validate our second hypothesis. A study of adult stimulant users in the United States found that the majority (73%) reported having at least one sexual risk behavior and only 38% used condoms consistently, although sexual risk factors were not associated with the HIV epidemic [40]. While others have found that an increase in the number of condomless anal sex partners could explain the fact that MSM who primarily inject methamphetamine were more likely to be diagnosed with syphilis and HIV [7]. In addition, we found an association between the number of sexual partners and condom use, which consistent with women who engage in sex work likely to use condoms more often [7].
ACEs exposure could predict infectious diseases in adulthoods, through both indirect and direct negative effects on infectious diseases by positively affecting adult injection of drug use, which supported the third hypothesis of this study. Previous findings that ACEs were associated with poor health outcomes in adulthood, such as increased risk of HIV and other sexually transmitted diseases [23, 41]. Whereas our study found ACEs contributed to a direct negatively effect on infection sexually disease. Possible reasons might be the mitigating effect of resilience on the potential long-term effects of ACEs, which may shape the mechanisms of benign resilience, a currently unquantified resilience that on the one hand mitigates childhood adversity and on the other hand avoids the emergence of risky behaviors in adulthood thereby reducing the risk of infectious diseases [26, 42]. Additionally, we found an association between ACEs and amphetamine-type stimulant abuse, and a study in Anhui Province, China, also showed that 44.6% of methamphetamine users reported negative childhood events [43].
ACEs exposure indirectly predicted infectious diseases by injection of drug use as a mediator. Firstly, drug injection was negatively associated with ACEs. In contrast, other scholars found that injecting drug use in adulthood was strongly associated with ACEs, and that early childhood maltreatment led to increased risk of substance abuse, as well as being a possible victim and perpetrator of HIV risk behaviors [44–46]. The characteristic of individuals with ACEs to partially or fully avoid negative health and social outcomes associated with childhood was called resilience, which was said to reduce the adverse effects of ACE [47]. The target population of this study may establish the negative outcomes associated with drug injection while growing up, thereby reducing the likelihood of injecting drug use in adulthood. On the other hand, ACEs exposure did not indirectly predict infectious diseases by condom use as a mediator, which was totally contrary with our hypothesis. Previous studies showed that ACEs were related to a lack of condom use and a higher number of sexual partners [48, 49]. The possible reason may be the low detection rate of infectious diseases in the target population of this study.
The association between cross-border behavior and infectious diseases could not be elucidated and failed to test the fourth hypothesis of the study. The reason may be that although people often engage in cross-border behaviors in border areas and cross-border marriages were common, the cross-border behavior was not a mobility factor due to the existence of one village in one country where people live in a stable manner for a long time and where socio-economic, psychological or other social behaviors were relatively similar. A previous study also showed that the differences in HIV, HCV and syphilis infection rates between Chinese and Myanmar nationalities were not significant, and reason may be the differences in high-risk sexual behaviors between people in cross-border marriages may not be significant over the long term. It may also be related to local infectious disease prevention and control policies, such as the fact that foreign women in cross-border marriages were equally entitled to resident health insurance and basic public health services [50].
Education, age, and gender were positively associated with injecting drug use, and age and education were correlated, with older adults being less educated, possibly because they were unable to receive an education when they should have for economic or developmental reasons. This study found that older and better educated individuals were more likely to inject drugs and had some similarities to other studies in which older adults with less than a high school education and a history of injecting drug use tested positive for blood-borne viruses more frequently [4]. Women maybe more likely to inject drugs and eventually developed infectious diseases, while men with ACEs were more likely to inject drugs. However, previous research has found that women may be more likely to be affected by multiple forms of abuse and poor mental health outcomes that later manifest as injecting drug use [45]. Ethnicity was negatively associated with drug injection; possible reasons for this may be that the local area was dominated by ethnic minorities, and that the greater pressure on Han Chinese to survive led to greater vulnerability to injecting drug behavior.
There were several weaknesses in this study. Firstly, the ACEs were measured via self-recall, which resulted in information bias. Secondly, the cross-sectional design could hamper the ability to derive causation. Furthermore, SEM suggested pathways that were not inclusive, with few directly observed variables and no potential variables that could influence exposure and outcome, which could limit causal interpretation. Finally, the study was limited to drug users in the treatment center, without non-drug users as controls, as well as most participants being mostly Dai male patients, thus restricting the generalizability of this study.