European Journal of Cardiovascular Medicine

Schizophrenia is a chronic and severe psychiatric disorder that profoundly affects thought, perception, and behavior, often leading to significant functional disability and poor quality of life. Globally, its lifetime prevalence is estimated to range between 0.5–1%, marking it as one of the most disabling mental illnesses [1]. A major clinical concern in this population is the high rate of comorbid substance use disorders (SUDs), with studies consistently reporting prevalence rates between 30% and 50%, far exceeding those seen in the general population [2,3].

Several mechanisms have been proposed to explain this vulnerability, including the self-medication hypothesis for negative symptoms and antipsychotic side effects, maladaptive coping strategies, social isolation, and underlying neurobiological alterations [4]. The most commonly misused substances are tobacco, alcohol, and cannabis, with tobacco use being particularly widespread among individuals with psychotic disorders [5]. The coexistence of SUDs in schizophrenia is associated with adverse outcomes such as poor medication adherence, frequent relapses, increased hospitalization, greater risk of violence, and an overall unfavorable prognosis [6].

Despite the considerable clinical impact, the prevalence and patterns of substance use among individuals with schizophrenia vary widely across regions, shaped by sociodemographic, cultural, and healthcare-related factors. Hospital-based studies remain crucial in elucidating these trends and guiding the development of integrated, context-specific interventions.

The present study was conducted to determine the prevalence of substance use disorders and to evaluate their sociodemographic and clinical correlates in patients with schizophrenia attending a tertiary care hospital.

Study Design and Setting: This hospital-based observational study was conducted in the Department of Psychiatry, KIMS & RF General Hospital, Amalapuram, Andhra Pradesh, India. The study was carried out over a period from December 2020 to May 2021. Study Population: A total of 100 patients diagnosed with schizophrenia, attending inpatient and outpatient psychiatric services during the study period, were included. Diagnosis was established according to the International Classification of Diseases, 10th Revision (ICD-10) criteria. Inclusion Criteria: Patients aged between 18 and 60 years. Confirmed diagnosis of schizophrenia as per ICD-10. Willingness to provide informed consent and participate in the study. Exclusion Criteria: Presence of comorbid severe medical or neurological illness. Acute intoxication or withdrawal states at the time of assessment. Cognitive impairment precluding valid participation. Data Collection Tools and Procedure: Sociodemographic and clinical details, including age, gender, marital status, employment status, and duration of illness, were collected using a structured proforma. Substance use disorders were identified through detailed clinical interviews and validated screening instruments, applying ICD-10 criteria for substance dependence or harmful use. Functional status was assessed using the Global Assessment of Functioning (GAF) scale. Ethical Considerations: The study protocol was reviewed and approved by the Institutional Ethics Committee of KIMS & RF General Hospital, Amalapuram. Written informed consent was obtained from all participants after explaining the study objectives and procedures. Statistical Analysis: Data were coded and entered into Microsoft Excel and analyzed using SPSS version 26.0. Descriptive statistics (mean, standard deviation, percentages) were used to summarize sociodemographic and clinical variables. Associations between substance use and correlates were examined using chi-square test or Fisher’s exact test for categorical variables and independent t-test for continuous variables. A p-value <0.05 was considered statistically significant.

A total of 100 patients with schizophrenia were evaluated. The mean age of the study population was 35.6 ± 8.7 years, with males comprising the majority (68%). More than half of the participants were unemployed (54%), and nearly two-thirds were unmarried (61%). The mean duration of illness was 7.8 ± 4.2 years (Table 1).

Table 1. Sociodemographic and Clinical Profile of Patients with Schizophrenia (n = 100)

The overall prevalence of substance use disorder (SUD) was 38%. Tobacco was the most frequently reported substance (26%), followed by alcohol (18%) a. Multiple substance use was noted in 7% of patients (Table 2).

Table 2. Prevalence of Substance Use Disorders

Substance use was significantly higher among males compared to females (49% vs. 14%, p < 0.01). The prevalence was greater in the 25–40 year age group (44%) than in those aged above 40 years (21%). Patients who were unmarried or divorced demonstrated higher rates of substance use (42%) compared to married individuals (29%), although this difference was not statistically significant. Duration of illness beyond five years was associated with a significantly higher prevalence of SUD (45% vs. 27%, p = 0.04). Patients with predominantly positive symptoms showed a higher prevalence (41%) compared to those with negative symptoms (30%), though the difference was not statistically significant (Table 3).

Table 3. Correlates of Substance Use in Schizophrenia

Patients with comorbid SUD exhibited poorer functional outcomes. Their mean Global Assessment of Functioning (GAF) scores were significantly lower (48.3 ± 9.1) compared to those without SUD (55.6 ± 8.4; p < 0.05) (Table 4).

Table 4. Functional Impairment in Patients with and without Substance Use Disorder

The present study revealed that 38% of patients with schizophrenia had a comorbid substance use disorder (SUD), a finding that corresponds with earlier literature describing a high prevalence of substance misuse among individuals with psychosis [6]. Tobacco use was most frequent in our cohort (26%), consistent with reports identifying cigarette smoking as the predominant comorbidity and emphasizing its clinical and therapeutic implications in schizophrenia [7]. Alcohol (18%) and cannabis (9%) use were also notable, echoing previous evidence that multiple substances contribute significantly to the disease burden in this population [8].

Sociodemographic correlates demonstrated that males and younger adults were more likely to develop SUD, reflecting trends documented in large-scale studies, including the CATIE trial, which underscored male gender and early adulthood as major risk factors for substance use in schizophrenia [10]. Similarly, the higher rates among unmarried or divorced patients, though not statistically significant, align with the hypothesis that reduced social support may facilitate maladaptive coping through substance use [11]. Duration of illness also emerged as a determinant, with patients suffering for more than five years showing significantly higher rates of SUD, consistent with longitudinal findings that risk increases cumulatively with chronic illness [12].

From a clinical perspective, individuals presenting with predominantly positive symptoms reported greater substance use compared with those with negative symptoms. This observation supports integrative models suggesting that psychotic distress, including hallucinations and delusions, often triggers substance misuse as a self-regulatory attempt [9,11]. Importantly, patients with comorbid SUD had significantly lower functional outcomes, as reflected by reduced GAF scores. This aligns with meta-analytic evidence linking comorbidity to impaired adherence, higher relapse rates, and poorer social recovery [8,9].

Overall, the findings underscore the importance of routine screening for SUD in schizophrenia, especially among young male patients and those with chronic illness. Integrated, dual-focus treatment strategies addressing both psychotic symptoms and substance use are essential to improve prognosis and functional recovery. Nevertheless, limitations such as the cross-sectional, hospital-based design and modest sample size restrict causal inference. Future multicentric, longitudinal research is warranted to confirm these associations and guide targeted intervention strategies.

This hospital-based study highlights the high prevalence of substance use disorders among patients with schizophrenia, with more than one-third of the sample affected. Tobacco, alcohol, and cannabis were the most commonly used substances, with tobacco predominating. Substance use was significantly associated with male gender, younger age, and longer duration of illness, and was linked to poorer functional outcomes as reflected in lower GAF scores. These findings underscore the importance of routine screening for substance use in psychiatric settings and the need for integrated, dual-diagnosis approaches that address both psychosis and comorbid substance use simultaneously. Such interventions may improve treatment adherence, reduce relapse rates, and enhance long-term functional recovery.

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