Introduction
Psychological disorders are among one of the main global health concerns. Despite advancements in treatment programs in the past two decades, the prevalence of these disorders is showing an alarming increase [1]. Nearly 970 million people, constituting 12% of the world’s population, suffer from psychological disorders, mostly residing in low- and middle-income countries [2, 3]. Psychological disorders, including depression, contribute substantially to disability-adjusted life years [4]. The COVID-19 pandemic increased the prevalence of depression in people, emphasizing the urgency needed for preventive and intervention measures [5]. A systematic review study revealed a noteworthy surge in the global prevalence of depression, particularly in certain Asian countries, following the COVID-19 outbreak [8]. In Iran, various studies have shown varying depression prevalence rates, with higher rates in women and residents of rural areas and small towns [13]. The studies conducted after the COVID-19 pandemic in Iran have reported a surge in depression prevalence, especially among specific demographic groups [14-20]. There is a lack of information regarding the current state of mental health in the Iranian community. Therefore, this study aims to investigate the prevalence of depression and the associated demographic and socio-economic factors among people aged ≥15 years in Iran.

Methods
This is a descriptive-analytical population-based study that was conducted from February to April 2023. Based on the 2015 national population and housing census [23], the study population consists of all Iranian citizens aged 15 and older (n=60,733,605). The sample size was determined using Cochran’s formula, which was 3,018, considering a 10% sample dropout. A multistage stratified sampling approach was adopted for recruiting samples from different provinces based on the inclusion criteria (residency in Iran, verbal communication ability to respond to the questions, age ≥15, and voluntary informed consent). Exclusion criteria were unwillingness to continue the interview and giving incomplete answers.
The information was collected through telephone interviews using the Computer-Assisted Telephone Interviewing (CATI) system. Questionnaires were used for data collection, including demographic and socioeconomic factors and the Patient Health Questionnaire (PHQ-2). Descriptive statistics, including frequency, percentage, mean, and standard deviation were computed in SPSS software, version 21. Hypotheses were tested using Welch’s t-test and logistic regression analysis. The significant impact of independent variables on the dependent variable was examined using the Wald test and likelihood ratio test in the “lmtest” package in R software. P<0.05 was considered statistically significant.

Results
Of 3,018 individuals who participated in the interviews, 126 were excluded due to incomplete responses. Therefore, the analysis was done on 2,892 respondents. Their mean age was 43.6±16.9 years (42.6 for women and 44.7 for men). Utilizing the PHQ-2 tool and based on a cut-off point of 3, the study revealed that 1,218 people (42.1%) had clinical depression symptoms, while 1,674 people (57.9%) did not manifest depression symptoms. The depression prevalence rate was 44.6% for women and 39.6% for men, with mean depression scores of 2.52±1.71 and 2.25±1.83, respectively.
We analyzed the predictors of depression using the multiple logistic regression model, including gender, education, age, place of residence, marital status, income, and housing status. The findings revealed that housing status (β=-0.30, OR=0.74, P=0.000), being single (β=0.41, OR=1.51, P=0.002), being widowed/widower (β=0.40, OR=1.50, P=0.020), being divorced (β=0.51, OR=1.67, P=0.023), having an academic degree (β=-0.42, OR=0.65, P=0.001), unemployment (β=0.40, OR=1.50, P=0.011), age 25-40 (β=0.33, OR=1.39, P=0.050), and being a homeowner (β=-0.30, OR=0.74, P=0.001)  had significant associations with depression (Table 1).



Conclusion
In this study, it was found that 42% of Iranian people had major depressive disorder. This prevalence indicates a high number of individuals experiencing depression, but due to the relatively low predictive value of 3 as the cut-off point of the PHQ-2 [32], there may be a potential for overestimation. Although women showed higher depression rates, the gender factor was omitted from the multivariate regression model, emphasizing the need for a comprehensive approach beyond gender. The 25-40 age group exhibited marginally higher depression rates than the age group 15-25. No significant association between place of residence (rural/urban) and depression prevalence was observed. Education emerged as a protective factor, where people with a university education shower lower depression rates. Unemployment was associated with higher depression prevalence, underscoring the psychosocial impact of economic instability. Marital status played a significant role, where single, divorced, and widowed/widower individuals experienced higher depression rates than married people. The people with an income level of 8-10 million Tomans showed significantly lower depression rates. However, the income level was omitted from the multivariate regression model. This study provides valuable insights into post-COVID depression prevalence in Iran. The nuanced relationships between depression and some demographic and socio-economic factors underscore the importance of comprehensive, multivariate analyses in understanding mental health dynamics.

Ethical Considerations

Compliance with ethical guidelines
All ethical considerations were considered in this study. The study was approved by the Ethics Committee of the Faculty of Psychology and Education, University of Tehran (Code: IR.UT.PSYEDU.REC.1403.003).

Funding
This study was funded by the Strategic Center for Culture and Media in Tehran, Iran.

Authors contributions
Conceptualization and original draft preparation: Soroush Zolghadri; Methodology, data collection, and Formal Analysis: Majid Hadavi; Editing and supervision: Hadi Bahrami Ehsan.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgments
The authors would like to thank the Strategic Center for Culture and Media and the University of Tehran for their support and all the individuals who participated in this study for their cooperation.