Introduction
Drug addiction is a serious global health problem caused by physical, psychological and social disorders, and it is a major factor in increasing suicide risk [
1]. In a record analysis, 43.9% of drug addicts had suicidal behaviors [
2]. According to the United Nations Office on Drugs and Crime World Drug Report 2022, approximately 300 million people around the world took drugs this year, making drug use a global issue. In June 2022, the Chinese government website released “Drug Situation in China (2021)”, which showed that there were 1.486 million drug addicts nationwide. Although it decreased by 17.5% compared to last year, the drug situation was still severe. In China, the pooled prevalence of illicit drug use was about 2.10%, and Sichuan showed a high prevalence [
3]. A study showed that 83% of drug addicts were addicted to multiple drugs, and 68% of drug addicts preferred oral administration, while 32% used drugs through a combination of oral, inhalation, and injection routes [
4]. At the same time, multiple prospective studies have shown that drug addiction is strongly related to mental problems [
5,
6], including depression and anxiety [
7], and these psychiatric problems and drug addiction are common comorbidities in psychiatry.
Hostility is a negative attitude of antagonism and hatred towards others, characterized by distrust, irritability [
8], and high aggression [
9]. The severe hostility of drug addicts can lead to extremely autonomous and aggressive behaviors that are not conducive to social stability. Criminal tendencies are often associated with violent behaviors among drug addicts, and 39.68% of drug addicts have a history of violent behaviors [
10], with the prevalence of violent behaviors among female drug addicts significantly higher than among male drug addicts (63.3% vs. 24.2%) [
11]. Such people are vulnerable to discrimination and unfair treatment in society, which in turn increase their level of hostility. Several studies have shown that hostility is associated with physical ailments [
12‐
14], such as heart disease and chronic obstructive pulmonary disease, which affect the physical and mental health of individuals. Depression is usually a negative emotion that has been defined as persistent sadness, hostility and irritability [
15]. Studies have shown that drug addicts have higher levels of depression than non-addicts (Mean = 32.70 vs. 17.77) [
16]. The prevalence of depression among addicts is high [
17]. One study showed that the incidence of severe depression among drug addicts was 44%, while the incidence of mild to moderate depression was 25% [
18]. Studies have found that 57.6% of the participants showed any type of mental symptoms, including depression, anxiety and psychotic symptoms [
19]. It can be seen that a larger proportion of drug addicts suffer from mental illness such as depression. At the same time, negative emotions such as depression are important reasons for drug addiction [
20,
21], and negative emotions of depression increase the likelihood of relapsing [
22]. In addition, some researchers have found a strong association between hostility and depressive disorder individuals with a high level of hostility having a higher level of depression [
23]. At the same time, individuals with severe depression also showed a higher level of hostility [
24]. According to previous studies, drug addicts generally have a high level of depression [
25]. In terms of gender differences in depression, psychologically, more females are depressed than males [
26]. A study of depression in adolescents found that common environmental factors had greater impacts on adolescent girls’ versus boys’ depressive symptoms (13% vs. 1%) [
27].
Sense of life meaning was defined by Steger as a positive variable, which was the perception of and search for purpose and value in one’s life [
28]. One study showed that the sense of life meaning was lower among drug addicts [
29]. A strong relationship has been documented between the sense of life meaning and depression in both high and low mental states [
30]. Researchers have shown that an increased sense of life meaning was associated with reduced depression [
31]. Episodes of depression are associated with a low level of life meaning and a high level of hostility. Therefore, more attention should be paid to the sense of life meaning of drug addicts. Researchers have included the sense of life meaning into the presence of meaning and the search for meaning [
28]. Various studies have confirmed that the two dimensions of sense of life meaning have different effects on psychological problems. The presence of meaning is negatively correlated with psychological problems such as depression [
32], while the search for meaning is positively correlated with depression [
33]. That is, positive life meaning helps maintain mental health. This study focuses on the negative relationship between sense of life meaning and depression, and examines how the presence of meaning affects depression.
Reducing depressive states is of great importance in promoting physical and mental health. However, few studies have investigated the relationship between sense of life meaning and hostility. And there are limited studies in special populations and gender differences, especially for drug addicts. It is also worth exploring whether the sense of life meaning can be a way to regulate hostility and improve depressive states. Therefore, there is a need to further discuss the role of sense of life meaning in the relationship between hostility and depression. Increasing the sense of life meaning is a guide to reducing depression levels among drug addicts, promoting effective drug prevention and improving social stability.
Methods
Design
The study was conducted from March to June 2022, and participants were informed of the purpose and confidentiality of their participation before the investigation. After signing informed consent, participants completed the Cook-Medley Hostility Scale (CMI), Beck Depression Inventory (BDI), and Meaning in Life Questionnaire (MLQ) questionnaires under the guidance of a professional instructor. We obtained research data through questionnaires completed by participants and distributed souvenirs and gifts to all participants.
Participants
Using simple random sampling to recruit participants. A total of 826 participants were investigated in this study. These participants were divided into two groups: drug addicts (233 males and 182 females) and non-addicts (174 males and 237 females). These addicts were recruited from two drug rehabilitation centers in Sichuan Province, China. Among drug addicts, about 82% were abstainers who used methamphetamine, while the rest used heroin, marijuana, and ketamine. The entry criteria for drug addicts were as follows: (a) Drug addicts who have completed physical detoxification and have a negative urine test. (b) Meeting the DSM-V diagnostic criteria for psychoactive substance abuse or dependence. (c) Absence of serious mental illness and not taking any medication, (d) Age 16–65 years old, and (e) Education background of elementary school or above.
Non-addicts (174 males and 237 females) were some college students and people employed in Sichuan Province, China. The entry criteria for non-addicts were as follows: (a) Absence of serious mental illness and not taking any medication, (b) Age 16–65 years old, and (c) Education background of elementary school or above. The purpose of the study was explained to the participants, and all participants signed informed consent before participation.
Measures
Cook-Medley Hostility Scale
The Cook-Medley Hostility Scale (CMI) was an indicator of health developed by Cook and Medley [
34]. The scale used in this research covered the 43-item subset determined by John C. Barefoot [
35], which included five dimensions, namely, cynicism, hostile affect, aggressive response, hostile attitude, and social aversion, with a total of 43 items. Higher total scores on the CMI indicated a higher level of hostility. In this study, the Cronbach’s Alpha value of CMI was 0.769 in drug addicts and 0.805 in non-addicts.
Beck depression inventory
The Beck Depression Inventory (BDI) was written by Beck in 1996 [
36] and was used to assess the severity of depressive symptoms within two weeks. This scale consisted of 21 items, each rated from 0 to 3. Higher total scores indicated a higher level of depression. In this study, the Cronbach’s Alpha value of BDI was 0.854 in drug addicts and 0.909 in non-addicts.
Meaning in life questionnaire
The Meaning in Life Questionnaire (MLQ) was written by Steger in 2006 [
28] and emphasized the meaning in one’s life. The MLQ included two dimensions: the presence of meaning and the search for meaning. The items of the MLQ were rated from 1 to 7, with higher total scores indicating a higher level of sense of life meaning. In this study, the Cronbach’s Alpha value of MLQ was 0.754 in drug addicts and 0.830 in non-addicts.
Statistical analysis
We used SPSS 25.0 and AMOS 24.0 for data entry, collation, and analysis. First, Harman’s one-factor test was used to test for common method bias. Second, descriptive statistics were used to analyze the demographic information of drug addicts and non-addicts. Moreover, measures such as age, BMI, CMI, BDI and MLQ among drug addicts and non-addicts were described by means and standard deviations (M ± SD) and compared by t-test. Third, Pearson correlation analysis was used to assess the correlation between variables. Fourth, linear regression models were used to assess the impact of hostility and depression among drug addicts and non-addicts. Meanwhile, gender, age, and BMI were controlled as covariates. Finally, we used AMOS 24.0 to establish intermediary models and used bootstrap mediation effect tests to further test the mediation effect of sense of life meaning. Statistical significance required a two-sided P-value of ≤ 0.05.
Limitations and directions for future research
Several limitations must be considered when interpreting the results of this study. First, the drug addicts recruited for this study are members of only two drug rehabilitation centers in Sichuan Province, which may limit the representativeness of the sample. Second, there are significant differences in age and BMI between the two groups, which reduce the comparability between the two groups in this study. Third, the sampling method may be the reason for the inconsistency of the conclusions with the previous. Fourth, this study adopted a cross-sectional design, which could not capture the psychological and emotional changes of individuals, such as hostility and depression.
For future research directions, some factors should be considered. First, in future studies, we should take into account the views of drug addicts on the number and duration of drug use, and minimize the intervention of drug factors in the study. Second, participants will be identified in the initial questionnaire as having a specific history of mental illness to ensure the accuracy of the study. Third, age should be taken into account in future studies and the role of age in the study should be analyzed. It is also important to control the consistency of demographic information and strengthen the comparability between groups when recruiting participants. Fourth, when analyzing the role of gender in research in future studies, it is also important to consider the differences that exist in gender itself, such as hormones and brain function. Finally, future research should enrich the sample by sampling a wider range of people and adopting a longitudinal study design to further confirm the influences of hostility and sense of life meaning on depression.
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