Based on the data, 3% of participants were female and 97% were male. This is probably due to lower rate of addiction among females or cultural barriers dissuading females from visiting treatment centers. In the west, males were twice more likely to develop drug problems than females. One study in Iran reported that females addicted to heroin seeking treatment, had high levels of depression and had poor social functioning (
9).
In the current research, in total, 48.96% of participants had depression and opium was the most prevalent substance used among clients (40.2%).
Abbasi et al. found that opium was the most abused substance among self-introduced addicts with a rate of 66.7% (
10). Parvizi Fard et al. reported that 66% of studied substance users had severe depression and 12% had anxiety (
11). Based on a research which was conducted by Ahmadvand et al. in Kashan, in 2008, the prevalence of psychological disorders in general population was 20% (35.5% female and 21.2% male). The prevalence of mood disorders was 9.3% (
12).
Depression was the most frequent symptom among opium users in Shiraz, Iran (
13). Sixty-seven patients from 200 patients (35.5%) on MMT referring to clinics in Sari, Iran, were depressed (
14). Mortazavi et al. conducted a cross-sectional study on elderly substance users. They showed that 28.1% of drug abusers had at least one psychiatric disease, among which major depression was the most common disorder (
15).
Also, in another research on patients with methamphetamine induced psychosis, depression (47.9%) was the most prevalent psychiatric disorder (
16). Current prevalence rates of depression among patients on agonist therapy were between 10% and 30%, which had negative effects on treatment outcome (
17).
Bryan K. Tolliver et al. reported that, the possibilities of having major depressive disorder for 12 months and entire life were 5.28% and 13.28%, respectively. Furthermore, 19.7% of substance users had at least one mood disorder during the last year (
5).
According to the acquired data of National Epidemiology Survey of America NESARC that the prevalence of major depressive disorder among substance users was 14.5%, while 19.2% of patients, who had major depressive disorder were substance users (
18). Peles et al. reported that half of their 90 participants (15 new patients and 75 on MMT) were depressed (
19). Prevalent psychological disorders (affective, anxiety and substance use disorders) usually occur simultaneously. In total, 25.4% of the patients, who had one of the mentioned disorders, had at least one disorder from another classification. Furthermore, 3.5% of them had three classifications of disorders, simultaneously (
20).
In a systematic review conducted in 2015, a strong relationship was recognized between substance abuse and major depressive disorder (OR = 3.8) (
4). In one research, it was shown that the prevalence of substance abuse disorder among those, who had psychical disorders was about 10.4% (
3). The current research found a significant negative relationship between depression level of addicts visiting self-presentation clinics and their age P = 0.1, so that by increasing age, depression level decreased.
In the current study, employment status and income were effective factors on depression among patients. Also, after logistic regression, patients’ income was a predictor of depression. In one research, depression, phobia, and anxiety were the most frequent disorders among patients treated by maintenance methadone. Furthermore, psychological disorders had significant correlations with simultaneous abuse of substances, family, and employment problems (
21).
Kosten et al. realized that addicts, supported by employment or criminal activities before seeking MMT, had better prognosis than patients supported by public assistance. Among them, the welfare group had the greatest improvement in substance abuse and psychological problems (
22). This research found that there was a significant relationship between depression and substance type. Logistic regression revealed that being a poly drug user might determine the possibility of having depression among patients. Todadze et al. showed that among opioid drug users undergoing OST, poly-drug users manifested the highest scores of depression and anxiety while buprenorphine users had the lowest rate (
23). Regarding the treatment period in the current study, longer treatment periods could increase the chance of depression among patients treated at the studied centers.
Peles et al. reported that depression scores of new patients were significantly lower than continuous treatment patients, independent of treatment duration (
19). In a research conducted in China, during year 2007, patients, who used methadone for treatment were monitored for three and six months. This research showed that dependence level and depression level had decreased significantly (
24). In a case-control study, methadone maintenance treatment stabilized the patients’ moods. The Difference between the two groups (MMT versus control) was significant (
25). In the current research, it seems that patients’ awareness of their lost past was probably the reason for being depressed during the treatment period.
To compare the depression of patients from two areas of residence (rural and margin of cities), living in margin of a city might be a determinant for patient’s depression (OR = 4). In one study, MMT patients at a rural district health center reported very high proportions of anxiety/depression (43.1%) compared to urban areas (
8). Wenyuan Yin et al. reported on factors associated with depression and anxiety among patients under MMT treatment. The prevalence of depression (SDS score ≥ 53) was 38.3% and only employment status (P < 0.001) was associated with depression. In this study, education level, marital status, method of drug use, and length of time in treatment were not significantly associated with depression (
26).
5.1. Conclusions
According to what has been mentioned, it can be concluded that depression is a highly prevalent disorder among addicts. Meanwhile, depression is related to factors such as age, job, income, area of residence, and treatment period. Therefore, special attention to mood disorders of patients in substance abuse treatment centers is highly recommended. To achieve this, training courses of technical assistance should necessarily include information about psychological disorders. Hence, considering mood changes during treatment helps therapists manage treatment. Special consideration of patients’ job status and income can lead to a faster recovery and treatment of mood disorders.