Our study, conducted to determine the prevalence of depression among inmates and the associated factors, revealed that 18.8% of the incarcerated individuals reported experiencing depression, as measured by the self-reported BDI-II screening tool. Moreover, having health problems, suicide attempts before imprisonment, and suicide ideation during imprisonment were associated with depression.

Similar results on the prevalence of depression as of our study were found in Nigeria, ranging from 14.8% [31] to 20.8% [14], and in India, with 25.7% [18]. However, the prevalence of depression among inmates in Gandaki Province was higher than the study conducted in France at 8.7% [32]. In contrast, our study’s result was lower than other studies done in Nepal, as 35.3% and 45.6% of the inmates had depression in eastern [5] and Dilibazar central Nepal [17], respectively. Similarly, other LMICs reported higher rates of depression among inmates, e.g., Ethiopia with 43.8% [33] and Malaysia with 40.7% [34]. Moreover, a meta-analysis conducted in 2020 suggested that the pooled prevalence of depression among inmates was 36.9%, and the prevalence was 19.1% when depression was measured with diagnostic tools [3]. The latter result is similar to ours; however, BDI-II is a depression screening tool, not a diagnostic, but is used prominently in categorizing the severity of depression. The differences in results among various countries could be due to different instruments for assessing depression and study settings. Similarly, the study design adopted also makes differences in reporting depression, and usually, cross-sectional studies report lower prevalence [3].

The difference in depression prevalence could be attributed to the varying geographic locations, socio-economic factors of inmates, and prison conditions [34]. Also, research has found that inmates could exaggerate the illness so that they could leave the prison, which is called malingering. The malingering may have exaggerated the depression among inmates studies [28]. Moreover, measurement tools such as BDI-II and the Patient Health Questionnaire (PHQ-9) introduce variability in prevalence rates due to differences in sensitivity and specificity. The PHQ-9 has a sensitivity and specificity of 88% [35] whereas BDI-II has 85% and 86% [27]. The patterns of questions asked in these tools also play a role in observing diverse prevalence rates of depression [36].

This study found a significant association between having health problems and depression. However, a study conducted in eastern Nepal did not find any statistically significant association between self-rated health and depression of inmates when controlled for other variables, although the relationship was significant in bivariate analysis [5]. Physical health declines may be associated with loss of functioning, feelings of hopelessness and helplessness, chronic pain, identity threat, and a need for increased social support, which can be challenging to obtain in incarceration. These factors may contribute to depression in inmate populations [37]. In our study, more than one-third of the inmates had self-reported health problems, and almost two-thirds were smoking in the past, which suggests that incarcerated adults are at peril of physical health issues and ultimately at risk of depression.

Furthermore, the study found a significant association between suicidal ideation during imprisonment and depression, consistent with the study conducted in eastern Nepal [5] and the USA [38]. Suicide ideation among inmates during imprisonment can be influenced by factors such as psychological distress, lack of social support, traumatic experiences, lengthy sentences and loss of hope, overcrowding, violence, and a history of previous suicide attempts [19, 39]. The prison environment, with its harsh conditions and separation from support networks, can contribute to feelings of hopelessness and isolation [40]. Additionally, pre-existing trauma, substance abuse, and a perceived lack of rehabilitation prospects can intensify the risk of suicide ideation [41]. Addressing these factors through comprehensive mental health support is crucial to prevent suicide ideation and promote rehabilitation [41].

Similarly, attempted suicide before imprisonment was found to be significantly associated with depression, which coincides with a previous study conducted among vulnerable prisoners and a separate study involving Northern Irish prisoners, which yielded similar results, indicating a strong association between prior suicide attempts before incarceration and depression [42]. Additionally, prisoners with a history of self-harm are more prone to exhibiting various depressive symptoms compared to their incarcerated counterparts without such a history [43]. This suggests an enduring susceptibility to self-harm and potentially suicidal tendencies among these individuals [42, 44]. This may be because individuals who have previously committed self-harm and/or exhibited suicidal behaviours may be particularly unable to cope with these initial stresses and be more likely to feel hopeless [45].

Meanwhile, socio-demographic characteristics, such as age, sex, marital status, education, ethnicity, occupation, and imprisoned time, were not associated with depression among the inmates. Similarly, a study in the regional prison of eastern Nepal [4] did not find any association with socio-demographic variables. However, a study conducted in India, and Western Ethiopia found that the age of the prisoners was associated with depression [18, 46, 47]. Inmates can have different levels of resilience and unique personality traits that make them different from individuals who have not committed crimes [48]. It is important to note that their criminal personality often has a stronger impact on their actions than their background or demographic characteristics before they commit the crime [48].

The study has several strengths and limitations. One of the key strengths of the study is its focus on an understudied population, highlighting the mental health concerns of inmates in Nepal. The study respondents were the representative of the Gandaki Province. Additionally, the study utilized a standardized measure for assessing depression, providing a reliable and valid measure of the participant’s depressive symptoms. However, the study also has several limitations. Although samples were representative of the whole province, it was a relatively small sample size, which caused the confidence interval to become wider.

This study is limited by self-reported data, which can be susceptible to recall bias. Inmates might be hesitant to admit to intentionally manipulating the system or forgetting instances of such behaviour. Additionally, malingering, where individuals exaggerate symptoms for secondary gain, is a documented concern in depression research among prisoners [28] and some respondents could have done that.

In addition, we could not check for the reverse causality on the association of suicidal ideation, attempt, and depression. We believe that depression could also cause suicidal ideation. Future studies could benefit from larger sample sizes and the inclusion of objective measures to supplement self-reported data. Moreover, extensive research is necessary to gain an in-depth understanding of the underlying factors contributing to depression in an incarcerated population. Despite these limitations, the study provides valuable insights into the mental health of inmates in Nepal, highlighting the need for interventions to address depression and other mental health concerns in this population.

The substantial prevalence of depression (18.8%) and suicidal ideation during imprisonment (13.0%) implies that inmates are vulnerable to mental health issues in the prisons. The strong association between pre-existing health issues, suicidal behaviour prior to incarceration, and depression suggests that many inmates enter prison with underlying mental health issues. These findings highlight the need for mental health screening, diagnosis, and treatment, along with suicide prevention interventions in prisons. Moreover, the study’s implications could be linked to the rehabilitation of inmates after their release from prison. The general population of Nepal has limited awareness of prisoners’ mental health, and social and cultural barriers hinder open discussions about mental health issues [49, 50]. As a result, released prisoners are less likely to seek mental health support and are more prone to re-offend [51]. Also, depression reduces inmates’ motivation for rehabilitation, affecting their participation in reintegration programs [39]. Hence, mental health promotion and prevention interventions targeted at inmates in prison have long-term effects after their release and resettlement in the community.