Comorbid psychiatric illnesses with injection drug use complicate management and put both caregivers and affected individuals in difficult situations. Understanding the issue of psychiatric comorbidities and concurrent substance use among opioid people who inject drugs is important in the context of pharmacotherapy and improved treatment outcomes.

The majority of our participants were male. Most of the participants were in the 15–24 age group, with a mean age of 25 ± 5.32 years. More than half of our participants had never been married, and the majority lived with nuclear family. The sociodemographic profiles of our participants were similar to those of participants in previous studies conducted by Yasir et al.²¹, Andreecia et al.²⁵, and Trouiller P et al.⁷. Similar findings were reported by Nizam Ud Din et al. in their study on substance users²⁶. However, in the study conducted by Andreecia et al.²⁵, the majority of the participants were married and older. Our study also included participants < 18 years of age, which could partly explain the lower age distribution and never married status of most participants. Equal representation of subjects from nuclear and joint families was reported by Yasir et al.²¹, while in our study, 79.9% had nuclear families. This can be explained by the difference in the settings (community vs. hospital-based) in which the studies were conducted.

In this study, all the participants were injecting heroin. Yasir Hassan et al.²¹ and Trouiller P et al.⁷ also reported 91.12% and 100% heroin users among PWID, respectively. However, Armstrong et al.²⁷ found buprenorphine to be the major injectable in 77% and heroin in 18% of the participants. This might be related to the availability of heroin in the study area. Nearly all of the participants had used tobacco products in the last three months. Alcoholic beverages, cannabis, and sedatives were used by 74.7%, 74.1%, and 50.9% of participants, respectively. However, these findings differed from those of the study conducted by Andreecia M et al.²⁵, in which the most commonly abused substance (barring tobacco products) with opioids was cannabis followed by alcohol. The results from the study by Yasir et al.²¹ reported lifetime use of cannabis, alcohol, and sedatives-hypnotics in 50.33%, 21.33%, and 18.33% of participants, respectively. This difference in the prevalence of use of these substances between our study and the study by Yasir et al. could be because the current study was based exclusively on opioid injectors.

The average age of initiation of injection drug use among our study participants was 21.77 ± 5.65 years. In a Delhi-based study by Gregory Armstrong et al. in 2013²⁷, the average age of initiation was lower (15.8 years). This age variation can be explained by the difference in the study population that was targeted by the researchers. Their study was community-based and targeted the hidden group with high injecting behaviour as opposed to our study. Peer pressure was the main reason for injecting behaviour among the majority of our participants, followed by curiosity and fun. This is in agreement with the findings of the study conducted by Samina Farhat et al. in 2015²⁰. The pressure to conform (to do what others are doing) can be powerful and hard to resist. A person might feel pressure to do something just because others are doing it. Peer pressure can influence a person to do something relatively harmless or something that has more serious consequences. The negative influence of the peer group is more connected to involvement in risk behaviours²⁸. Daily heroin use in the last 3 months was reported by 94.2% of the participants. In the study by Silvia Tortajada et al. in 2012⁶, the majority of the study participants used injection drugs one or two days a week, and only 16.2% used them every day. Nearly one-third of the participants had a family history of substance use. Another important finding of the current study was friends as the major path of referral. Treating one injection drug user can be the motivation for seeking treatment among other PWID, creating a positive cycle.

In our study, psychiatric comorbidities were found in 88.1% of the participants. This is similar to findings in other studies conducted in other parts of India, such as those by Farooqui et al. and Mohanty et al.^29,30, in which 98.6% and 77.5% of participants had psychiatric comorbidities, respectively. This difference in the prevalence can be explained by the difference in the measurement tools used in these studies. Studies from the West have reported a lower prevalence of psychiatric morbidities, 52.7% by Angelo Giovanni M. et al. in 2011¹⁰ and 43% by Silvia Tortajada et al. in 2012⁶. Approximately two-thirds of our study participants had more than one psychiatric comorbidity. However, this is slightly higher than the number in the study conducted by Farooqui et al. in 2022²⁹. This high burden of psychiatric comorbidities requires rigorous assessment of PWID for multiple disorders other than substance use disorders.

Anxiety disorders comprising panic disorder, agoraphobia, social anxiety disorder, and generalized anxiety disorder were found in most of the participants (66.5%). A slightly higher prevalence (71%) of anxiety disorders was also found in a study by Gregory Armstrong et al.²². Other studies had a significantly low prevalence of anxiety disorders^6,25. The higher prevalence of anxiety disorders can be explained by the unrest in Kashmir and the COVID-19 pandemic during the study period.

Nearly one-third (39.3%) of the participants had an antisocial personality disorder. This finding was consistent (44%) with those of the study by Robert K. Brooner et al. in 1993³¹. In a study by S. Darke et al.³², community-based methadone patients, prison inmates enrolled in prison methadone programs and prison inmates with no history of heroin use were interviewed to obtain a diagnosis of antisocial personality disorder (ASPD) and psychopathy. They reported that 44% of community-based methadone patients had ASPD, which is similar to the findings of our study³². Furthermore, any history of injecting drugs increases the odds of being diagnosed with an antisocial personality disorder by a factor of 21.01³³. ASPD poses a major challenge to health care providers, as the outcome remains poor.

Major depressive disorder was found in 17.7% of our study population. A similar prevalence of depressive disorder was found in the studies by Trouiller P et al.⁷ (21.3%), Margoob MA et al.³⁴, and Mary E. Mackesy-Amiti et al. (25%)^7,23. Only 3% of the participants in our study had psychotic disorders. PTSD was found in 8.5% of our study participants, which was in line with the findings by Margoob MA et al.³⁴. These findings could be attributed to local political unrest that causes trauma and discontent.

In our study, suicidality (excluding low intent) was experienced by 29.5% of participants. The study by Iskandar et al.⁵ showed a prevalence of suicidal ideation and suicide attempts ranging from 50 to 93% and 43–87%, respectively. There have been substantial variations in the prevalence of suicidality between studies. Suicidality has been difficult to compare owing to different risk assessment methods employed by different researchers⁵ and the inclusion of low intent in calculating the prevalence.

In the bivariate analysis, co-occurring substance use of codeine, oral tramadol, and tapentadol and the use of multiple drugs over time by PWID showed a significant relationship with the development of psychiatric comorbidities. Surprisingly, using a combination of opioids at a single point in time protected against psychiatric conditions in people who inject drugs. This finding of polysubstance use and an increase in psychiatric comorbidities in PWID is in line with those in the studies by Fischer et al.³⁵ and Mackesy-Amiti et al.²³, in which polysubstance use was associated with psychiatric comorbidities.

Cannabis use was significantly associated with major depressive disorder. This is in agreement with the studies by Daniel Feingold et al. and John Horwood et al.^36,37. There is a potential genetic correlation contributing to the comorbidity of cannabis dependence and major depression. Serotonin (5-HT) may mediate such an association, and there is also evidence for specific risk alleles for cannabis addiction³⁶. In our study, cocaine, amphetamine, and inhalant use were positively associated with obsessive–compulsive disorder. Daily heroin intake was negatively associated with psychotic disorders. These findings are similar to those of the study by Trouiller P et al. (2020), in which daily heroin use was negatively associated with major depressive disorder and psychotic disorders in PWID⁷. The hypothesis of an antipsychotic or modulatory effect of opioids on dopamine or on the neurotransmitter system that controls mood has been suggested^38–41. All substances except amphetamine and daily heroin intake were found to be significantly associated with anxiety disorders.

In the binary logistic regression, younger age was protective against psychiatric comorbidities. This can be explained by the cumulative effect of substances over time on the development of psychiatric comorbidities. This also calls for the need for early intervention among people who inject drugs to prevent the development of psychiatric disorders. Having never been married was also associated with more psychiatric comorbidities. The hypothesis for this finding can be ascribed to a lack of social support. In 1999, Rebecca S. Brienza et al. found that opioid users without a current partner were more likely to be depressed than those with a partner⁴².