Introduction
on-communicable diseases are responsible for the deaths of more than 35 million people each year [1]. Policymaking and managing the healthcare programs should know the burden of disease as the most objective evidence [2]. Schizophrenia, Bipolar Disorder (BD), and Autism Spectrum Disorder (ASD) have common genetic etiologies [3]. In developing countries such as Iran, the families of schizophrenia patients are involved in the long-term rehabilitation process [4]. Schizophrenia is a mental disorder characterized by distortions in thinking, emotion, behaviors, and perception of reality [5]. Schizophrenia is one of the most severe neuropsychiatric disorders [6]. According to the World Health Organization, schizophrenia is the eighth leading cause of disability-adjusted life year in the age group of 15-44 years worldwide [7]. In pathological systems, schizophrenia is mainly known as a set of signs and symptoms such as delusions, hallucinations, and disorganized speech and behavior [8]. One study showed a significant relationship between quality of life and coping strategies [9]. Patients with schizophrenia have low levels of education, income, and social status [10]. BD or manic-depressive illness, is associated with acute seizures [11, 12]. It is difficult to estimate the annual incidence of BD [11] accurately, and it appears that 20% of patients with clinical signs of depression are bipolar [12]. BD is a brain disorder that causes severe mood swings and changes in body energy levels [13, 14]. Drug adherence is low among patients with BD [15]. The performance of patients with schizophrenia and BD, as measured by the Wisconsin test, is poorer than the healthy population [16].
One of the most severe developmental disorders is ASD that occurs in early childhood (usually before the age of 3) [17]. A study showed that quality of life therapy increases the psychological wellbeing of mothers of children with ASD [18]. Another study showed that mindfulness-based treatment improves the quality of life and coping styles of mothers of children with ASD [19]. According to Zhang et al., the families of patients with BD undergo a lot of stress during the acute treatment and recovery period [20]. According to Matson et al., the variety and intensity of care roles may lead to psychological problems in family caregivers [21]. According to Ivey, the psychological burden of caring for a mentally ill person can reduce the quality of provided care [22]. The most critical causes of recurrence of mental disorders are discontinuation or irregular use of medication and disruption in the relationship between the patient and the family [23]. In most previous studies, the sample size is small, and the disease burden in the families of patients with depression and BD was generally measured and compared with each other. In most studies, the families of patients with schizophrenia and ASD and the relationship of disease burden with social and economic status and income have not been studied. The research and comparison of schizophrenia, BD, and ASD are necessary since they have a high disease burden, and all are disabling and chronic. Given the genetic similarities and overlap of symptoms in these three diseases, we aimed to compare the burden of these diseases using a larger sample size. In this study, we tried to answer how much the burden of these diseases is and what factors are related to the burden of these diseases.
Materials and Methods
This descriptive study was conducted on 450 patients (150 with schizophrenia, 150 with BD, and 150 with ASD). The sample size was determined using Cochran’s formula. The inclusion criteria were being 18 years or older, having at least a primary education, having a family member with one of the three diseases, having been diagnosed by a physician on an outpatient or inpatient basis, having the disease in the past year, and being under treatment, not being hospitalized in the past month (because the study outcome can be affected due to the reported high burden of disease in families). The exclusion criteria were unwillingness to continue study participation and having a cognitive disorder or any condition that can impede them from answering the questions correctly (e.g. Alzheimer disease). A sampling of patients with schizophrenia and BD was performed in Iran Psychiatric Hospital, Tehran Psychiatric Institute, and Rasoul-e Akram Hospital. Also, sampling of ASD patients was performed in Ali Asghar Hospital, Tehran Psychiatric Institute, and the Center for the Treatment of Autistic Disorders. From each center, 17 families were selected.
The short form of Zarit Burden Interview (ZBI-12) was used in this study. This questionnaire has 12 items measuring the burden of care on caregivers of patients rated on a Likert scale from 0 to 4 and has a total score of 0-48. Its acceptable validity and reliability have been shown in various studies [24]. For its Persian version, Navidian et al. reported a good validity based on the opinions of a panel of experts and test-retest reliability of 0.94 [25]. The Depression, Anxiety, and Stress Scale (DASS) were also used in this study to measure anxiety and depression in the family of patients with mental disorders. One copy of the questionnaires along with a demographic checklist (surveying age, gender, relationship with the patient, level of education, employment status, income level, medical history, etc.) was provided to the one accompanying the patient (spouse, parents, child over 18, sibling or other person living with the patient). Then, two more copies of the questionnaires and the checklist were given to the patient and asked him or her to be given to two other family members/partners. The obtained data were analyzed in SPSS v. 22.
Results
According to Table 1, the mean±SD age of the caregivers was 43.27±0.70 years, and there was a significant difference between the three groups of caregivers in terms of age (P=0.001).


The highest hours of patient care were related to the caregivers of ASD patients, but there was no significant difference between the three groups (P=0.023). The highest hours of respite care were related to the caregivers of schizophrenia patients, but there was no significant difference between the three groups (P=0.034).
According to Table 2, the number of female and married caregivers was higher in all three groups.




In terms of occupation, most of the caregivers in the schizophrenia group were housewives (28%), while most caregivers in the BD and ASD groups were employed (32% and 51.3%, respectively). More than 92% of caregivers of patients with schizophrenia had no history of mental illness. Most of the caregivers in the three groups had no record of chronic disease. In the schizophrenia group, the highest income level of caregivers was 10-30 million Rials (42%), while in the BD group, most of them had income level <10 million Rials (20.7%). In the ASD group, most caregivers had no income (36.7%). According to Table 3, the mean burden of the disease reported by caregivers in patients with ASD was 23.54, which was more than those of BD and schizophrenia.


The mean burden of BD (19.87) was higher than that of schizophrenia. There was a significant difference in the mean ZBI-12 score between the three groups (P<0.05). The mean DASS score in the three groups of schizophrenia, BD, and ASD was 18.36, 18.39, and 22.91, respectively.
Discussion and Conclusion
In this study, the mean burden of the disease reported by caregivers of patients with ASD was 23.54, which was more than those of BD and schizophrenia. The mean burden of illness of BD (19.87) was higher than that of schizophrenia. There was a significant difference between the three groups regarding the mean ZBI-12 score (P<0.05). The mean DASS scores in the three groups of schizophrenia, BD, and ASD was 18.36, 18.39, and 22.91, respectively. There was a significant difference in the mean DASS score between the three groups (P<0.05).
The linear correlation coefficient for the mental status of caregivers for the total patients was 0.574, indicating a moderate correlation between the independent variable and the dependent variable. The effect size (0.524) revealed that independent variables could predict more than 52% of the changes in the dependent variable, and the remaining 48% is explained and predicted by variables that were not included in the regression model. This model had a good fit for explaining the dependent variable (P=0.0001). 
The linear correlation coefficient for the mental status of schizophrenia patients’ caregivers was 0.566, indicating a moderate correlation between the independent variable and the dependent variable. The effect size (0.320) revealed that independent variables could predict 32% of the changes in the dependent variable, and the remaining 78% is explained and predicted by variables that were not included in the regression model. This model had a good fit for explaining the dependent variable (P=0.0001). The results regarding the burden of three diseases are consistent with the findings of Navidian (2010) [34].
The linear correlation coefficient for the mental status of BD patients’ caregivers was 0.474, indicating a moderate correlation between the independent variable and the dependent variable. The effect size (0.422) revealed that independent variables could predict 42% of the changes in the dependent variable, and the remaining 58% is explained and predicted by variables that were not included in the regression model. This model had a good fit for explaining the dependent variable (P=0.0001). 
The results of this study regarding the financial burden are consistent with the results of Shamsaee et al. (2010) conducted on the needs of family caregivers of bipolar patients. They showed that a large percentage of bipolar patients’ family caregivers have financial needs [35]. In a study conducted on patients with schizophrenia admitted to Imam Reza Hospital in Bojnourd, Iran, the disease burden was higher in female caregivers than in male caregivers [36], which is consistent with our results. In a comparative study of mental disorder burden in the family caregivers of patients with depressive disorder, BD, and schizophrenia by Sadeghi et al. The stigma of the disease among the family caregivers of bipolar patients was higher than those of schizophrenia patients, which is consistent with our results.
The linear correlation coefficient for the mental status of ASD patients’ caregivers was 0.504, indicating a moderate correlation between the independent variable and the dependent variable. The effect size (0.254) revealed that independent variables could predict more than 25% of the changes in the dependent variable, and the remaining 75% is explained and predicted by variables that were not included in the regression model. This model had a good fit for explaining the dependent variable (P=0.0001).
This study had some limitations such as lack of literature in Persian about the subject, lack of cooperation of some caregivers in answering some questions, intentional mistakes in answering due to poor psychological conditions and fatigue in a small number of caregivers, and getting help from others to answer some questions. The governmental counseling centers should hold strategic classes for family caregivers to reduce the burden of diseases because they belong to low-income families. Moreover, when obtaining information, the researcher should pay more attention to the mental condition and readiness of caregivers. Different methods to reduce the burden of diseases in caregivers, such as lowering care hours and using respite care and respite recess and dividing tasks between caregivers, using social or daycare services, can reduce the symptoms of depression and anxiety in them. Caregivers’ mental health monitoring is also recommended as part of the patient’s care package, and pharmacological and non-pharmacological measures should be used to treat their depression and anxiety.
Given that women constitute the majority of caregivers, long-term planning using educational interventions should be done for their needs and concerns. In future studies, it is recommended to investigate the facilities available in the houses of caregivers (e.g. the number of rooms) and assess their special care abilities and talents to use these facilities and capabilities to reduce the burden of these diseases. Furthermore, the relationship of interior design, decoration, and arrangement of furniture in caregivers’ houses, the number of building units, neighborhoods, cities and villages, and different climates, as well as the job performance of caregivers with the burden of three diseases should be assessed. It is recommended that further studies be conducted using online questionnaires anonymously, and the results are compared with those studies where questionnaires were completed in person.

Ethical Considerations
Compliance with ethical guidelines
All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages. They were also assured about the confidentiality of their information. They were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors' contributions
All authors equally contributed to preparing this article.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
We want to thank the esteemed professors of the Faculty of Psychiatry of Iran University of Medical Sciences and the staff and patients of Iran Psychiatric Hospitals and Rasoul Akram (PBUH) and Ali Asghar (AS) and the staff of the Tehran Psychiatric Institute and the management and students of Ain Mehrvarzi School.


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