|Year : 2018 | Volume
| Issue : 1 | Page : 69-78
Role of perceived family environment in the pathogenesis of schizophrenia
Roshan Lal Dewangan1, Promila Singh1, Tanmay Mahapatra2, Sanchita Mahapatra2
1 School of Study in Psychology, Pandit Ravishankar Shukla University, Raipur, Chhattisgarh, India
2 Mission Arogya Health and Information Technology Research Foundation, Kolkata, West Bengal, India
|Date of Web Publication||29-Mar-2018|
Dr. Roshan Lal Dewangan
Pandit Ravishankar Shukla University, Raipur - 492 010, Chhattisgarh
Source of Support: None, Conflict of Interest: None
Background: Family plays an important role in mental health of its member, thus its contribution can also be discerned in pathogenesis. Maintenance and relapse of several mental illnesses have been also attributed to the family environment (FE). This study explores FE as perceived by schizophrenia patients. Methodology: A case–control study was conducted in Chhattisgarh, India, to measure the association of perceived FE with schizophrenia. Between February 2014 and January 2015, 100 paranoid schizophrenia patients and 100 neighborhood-based healthy (based on 28-item General Health Questionnaire) controls were recruited. Minimum school-educated individuals aged 20–35 years were eligible if they/their caregivers provided consent. Interpersonal relationships and FE were assessed by an interviewer-administered 69-item FE scale. Results: The odds of suffering from schizophrenia increased with age, decreased with education, income, and found to be less among married. Schizophrenia risk was negatively associated with mean scores for cohesion, acceptance/caring, active-recreational orientation, and organization. Negative symptoms of schizophrenia were less pronounced among patients belonging to joint families. Conclusion: Thus, to minimize the burden and morbidity associated with schizophrenia, interventions to improve FE by minimizing conflict and improving cohesion, acceptance/caring, active-recreational orientation, and organization, and specifically targeting older, less-educated, poor, and married individuals in nuclear families seemed necessary.
Keywords: Family environment, family intervention, schizophrenia
|How to cite this article:|
Dewangan RL, Singh P, Mahapatra T, Mahapatra S. Role of perceived family environment in the pathogenesis of schizophrenia. Indian J Soc Psychiatry 2018;34:69-78
|How to cite this URL:|
Dewangan RL, Singh P, Mahapatra T, Mahapatra S. Role of perceived family environment in the pathogenesis of schizophrenia. Indian J Soc Psychiatry [serial online] 2018 [cited 2020 Jan 23];34:69-78. Available from: http://www.indjsp.org/text.asp?2018/34/1/69/228794
| Introduction|| |
Familial conflict, neglect, lack of necessary support, and expected warmth together constitute risky familial environment effecting the mental health of young growing members. Regardless of psychiatric condition, parental maltreatment was associated with a number of neurological and behavioral pathologies of children. Specific to schizophrenia, inconsistent rearing practice and poor relationship with both the parents have been suggested to be associated with the later development of schizophrenia in children., Several attempts have been made to understand schizophrenia and its pathogenesis in the family context of schizophrenia patients. Birth order of the schizophrenia patient was a very early variable which was noted as to increase the propensity to develop schizophrenia; however, later, researchers declined these inconsistent findings., Attitude of mother, which is widely known as “schizophrenogenic mother,” and father gained sufficient attention from several researchers.,,,,, Researches from India investigated parental attitude of schizophrenia patients, however findings were not consistent.,,
Findings of Bateson et al. and Wynne et al. on communication style in family of schizophrenia patient had a great influence on family therapy practitioners. Further, significance of communication style was highly popularized after Brown  reporting on schizophrenic relapse, and a surge of studies started in the area of “expressed emotion.”,,, However, these researches explained much of schizophrenic relapse rather than contribution of family variables in genesis of schizophrenia. Murray Bowen, one of the leading family therapists, in the 1960s conceptualized the role of family members and their “undifferentiated self” in the development of schizophrenia pathology. Based on the available literature, this appeared to be the initial effort to understand the role of familial environment in this part of India, in the pathological development of schizophrenia, however several aspects of family life, such as burden on caregivers and well-being,,,,,, have been studied elsewhere.
Given there is a possibility to modify the course of schizophrenia by early diagnosis and appropriate interventions, leading to better treatment outcomes and speedy recovery, researchers have realized that, to prevent the disease onset or to minimize the associated distress, the most crucial step is to identify the at-risk population for developing such illness and then to plan for preventive strategies. Thus, a deeper understanding of complex interplay between environment (including family) and schizophrenia seemed to be the need of the hour either to prevent the disease or to improve the overall quality of life for people suffering from it. To gain more insights into the ailment, extensive research was conducted in India on biology (various metabolites and hormones), psychopathology, substance use, psychology, quality of life, rehabilitation, perception of burden by caregivers, and advances in treatment. However, till date, there is a dearth of information on the role of perceived socioenvironmental characteristics of family in its pathogenesis, which in the context of Indian society seemed critical. The present study was conducted to explore the perception of family environment (FE) among patients with schizophrenia in Indian context so that a tailored plan of care and support services could be designed and implemented early for better control of the illness. We also looked for the association between certain demographic variables and schizophrenia pathology.
| Methodology|| |
Between February 2014 and January 2015, 100 (56 males and 44 females) paranoid schizophrenia cases (diagnosed according to the International Classification of Diseases-10th Edition) were recruited from the inpatient departments of two psychiatric hospitals (Postgraduate Institute of Behavioral and Medical Sciences, Raipur, and Central India Institute of Mental Health and Neurosciences, Durg) in Chhattisgarh state of India. During the same time span, 100 population-based healthy controls (54 males and 46 females) were selected from the neighborhood (residence, youth clubs, community centers, educational institutions, etc., in the community) of the selected cases. While recruitment of each participant, a trained clinical psychologist or psychiatrist ensured that both cases and controls were aged between 20 and 35 years, high-school educated, could read and write Hindi (the local language), as well as provided written voluntary informed consents. The age criteria were determined based on the principal age of onset of schizophrenia in Indian population., The educational requirement was to ensure that assessment of FE could be done using a standard scale. Individuals who were previously diagnosed or currently suffering from any other psychiatric illness or chronic diseases were excluded from the study. Prior to recruitment, consenting potential controls were screened by a 28-item General Health Questionnaire  to rule out psychiatric morbidity.
Information on sociodemographic characteristics including age, gender (male/female), education (school level/college level/graduation and above), marital status (currently married/unmarried/divorced/widowed), monthly income (≤INR 5000/INR 5001–10,000/INR 10,001–20,000/> INR 20,000), place of residence (rural/urban), and family type (nuclear/joint) was collected from each participant on sociodemographic information sheet. Family Environment Scale-BC  scale was used for assessing individual's perceptions of the familial climate. It measured eight subdomains (subscales): (i) Cohesion (13 items, maximum score = 65), (ii) expressiveness (9 items, maximum score = 45), (iii) conflict (12 items, maximum score = 60) (iv) acceptance and caring (12 items, maximum score = 60), (v) independence (9 items, maximum score = 45), (vi) active-recreational orientation (8 items, maximum score = 40), (vii) organization (2 items, maximum score = 10), and (viii) control (4 items, maximum score = 20). Overall, it had 69 items and each item was rated on a 5-point Likert scale (1–5). A particular dimension is predicted by increasing score, except for conflict dimension where higher score suggests lesser conflict. Severity of positive and negative symptoms of schizophrenia was assessed using the Scale for Assessment of Positive Symptoms  and Scale for Assessment of Negative Symptoms.
The study content and procedure were reviewed and approved by the Institutional Ethics Committee of Pandit Ravishankar Shukla University, Raipur (Reference No. 038/IEC/PRSU/2014). Informed consent was obtained from each eligible participant and caregivers also.
Descriptive analysis of the study participants was conducted to determine the distribution of the sociodemographic and FE-related factors among cases and controls. Simple and multiple linear regressions were conducted, respectively, to determine the unadjusted and adjusted associations (β-coefficients with corresponding 95% confidence intervals [CIs] and P values) between sociodemographic characteristics and subdomains of FE as well as sociodemographics and FE with positive and negative symptom scores. Simple and multiple logistic regressions were similarly performed to measure the unadjusted and adjusted associations (odds ratio [OR] and adjusted OR [AOR], respectively, with corresponding 95% CIs and P values) of sociodemographic factors and FE with risk of schizophrenia. In the adjusted models, the association of each sociodemographic factor with FE, risk of schizophrenia and symptom scores, was adjusted for all others, while for the association of FE with risk of schizophrenia and symptom scores, the model was adjusted for age, gender, education, marital status, income, residential area, and family type. All data analyses were conducted using SAS statistical data analysis software Version 9.3.2 (SAS Institute Inc., Cary, NC, USA).
| Results|| |
The overall mean age was 25.02 years and cases were slightly older than controls (25.80 vs. 24.23 years, respectively). Among all the participants, 49.50% (more among controls) had college level of education and 81% (more among controls) were unmarried. The mean scores for FE were lower among cases than controls [Table 1] for seven out of eight subdomains (cohesion, conflict, acceptance and caring, independence, active-recreational orientation, organization, and control,) while for expressiveness, it was marginally higher among cases compared to controls.
|Table 1: Distribution of the study parameters among participating individuals (N=200)|
Click here to view
Among schizophrenia patients, with increasing age, the likelihood of having active-recreational orientation increased slightly. Compared to school-educated patients, those having college-level education had quite high mean predicted score for conflict. Relatively higher income was associated with lower mean predicted score for acceptance and caring adjusted β-coefficient [AC] as well as active-recreational orientation [Table 2]a.
Among controls, relatively higher income was negatively associated with mean predicted scores for cohesion, as well as active recreational orientation while it was positively associated with expressiveness. Compared to rural, urban controls were more likely to have better active-recreational orientation [Table 2]b.
With increasing age, the odds of suffering from paranoid schizophrenia increased marginally (AOR = 1.13, 95% CI = 1.00, 1.28). A significant negative association was observed between education and risk of schizophrenia (for college-level education: AOR = 0.13 [0.06, 0.29]). Participants who were unmarried as against currently married (AOR = 0.04 [0.01, 0.24]) and those having monthly income between Rs. 10,001 and 20,000 as against monthly income of < Rs. 5000 (AOR = 0.11 [0.02, 0.55]) were less likely to be schizophrenia case.
The odds of suffering from schizophrenia diminished with increase in mean scores for cohesion (AOR = 0.91 [0.85, 0.98]), acceptance and caring (AOR = 0.89 [0.82, 0.97]), active-recreational orientation (AOR = 0.85 [0.76, 0.95]), and organization (AOR = 0.72 [0.57, 0.91]) [Table 3].
|Table 3: Association of sociodemographic factors and domains of family environment with risk of schizophrenia among participating individuals (n=100)|
Click here to view
We did not find any statistically significant (at α =0.05) association (both unadjusted and adjusted) between sociodemographic factors and severity of positive/negative symptoms of schizophrenia except for joint families where both positive and negative symptom scores were likely to be less severe (for positive symptoms: unadjusted β-coefficient = −2.79, 95% CI = −5.42, −0.17); for negative symptoms, AC = −5.07 (−8.78, −1.37) compared to nuclear families. Similarly, mean scores for the domains of FE did not show any significant association with the severity of positive or negative symptoms of schizophrenia except for active-recreational orientation, mean score of which was negatively associated (AC = −0.39 [−0.76, −0.03]) with positive symptom scores of schizophrenia [Table 4].
|Table 4: Association of sociodemographic factors and domains of family environment with positive and negative symptoms of schizophrenia among participating individuals (n=100)|
Click here to view
| Discussion|| |
In this case–control study, 100 cases of paranoid schizophrenia and 100 neighborhood controls were compared regarding their socioeconomic distribution and FE. Cases were less educated compared to controls which corroborated with previous findings  and this may be the reason that unmarried individuals were higher among controls as they were still pursuing higher education as well as younger than cases. Higher marriage rate in schizophrenia can be explained in the context of Indian cultural perception that marriage can treat mental illness. Poor educational attainment has been associated with schizophrenia.,
In this study, the risk of suffering from schizophrenia was found to increase with advancing age although prior evidences using age categories indicated that the risk of schizophrenia was highest among young adults. Although we did not find gender to be a significant correlate for the risk of schizophrenia, both a systematic review  and meta-analysis  reported a higher risk of schizophrenia among men compared to women. Absence of the association in our study could be explained by the possibility that women schizophrenia patients might have limited access to psychiatric care or might be underdiagnosed than men in the study population.
Poorer individuals (income <Rs. 5000) were marginally higher among cases. Mean scores for several protective dimensions (acceptance/caring and active recreational) were less common among cases with relatively higher monthly income. Regression analyses also suggested that the middle-income group (Rs. 10,001–20,000) was having lower risk of schizophrenia. We propose an explanation that possibly poorer group has several nutritional, poor housing, and health-care status, whereas stigmatized status of schizophrenia in Indian community kept the high-income families away from the psychiatric medical centers and accessing health care privately. This explanation is further required to check. Previous studies also showed that low or high socioeconomic status was found to be associated with at least moderate risk of schizophrenia.
However, joint family has been described as a protective factor by virtue of having strong support system, and despite our findings that cases in joint families have less severe positive and negative symptoms, individuals living in joint families were more among cases. Distribution of gender and residential area (urban/rural) was similar among cases and controls. Age, gender, and residential area did not show any association with FE in both simple and multiple regression models.
Similar to prior studies,,, we found that, after adjusting for confounders, the risk of schizophrenia was higher in urban areas compared to rural residence, though the result was not statistically significant. A recent research suggested that urban childhood environment might be associated with later development of psychotic disorder. The differential risk pattern across the place of residence is not fully understood, but some hypothetical explanations included pre- and post-natal infections, migration, genetic factors, and access to psychiatric services.
In this study, we found FE to be a significant correlate of the risk of having schizophrenia among our study participants. Among the domains of FE, lack of cohesion was found to be a significant predictor of schizophrenia in a prior research,, which corroborated with our findings. Perhaps, the internal support and perceived commitment of the family as measured by cohesion helped to minimize the risk of schizophrenia. Higher acceptance and caring, active-recreational orientation which measured the emphasis in FE on participation in social and recreational activities of the family members, organized and structured planning for the activities and responsibilities in the family, and less conflict were features of FE of healthy controls.
Our study had some important limitations. First, by design, the data were collected through self-reports, which could have easily suffered from some social desirability and recall bias, especially among cases, leading to generate the potential for misclassification and miss-measurement. Although based on the robustness of the used tools and the compassionate environment of the hospitals where the interviews were conducted, we believe that this potential will be less in magnitude. Second, because of the case–control design, temporal ambiguity was always a possibility in this study. Hence, conditions such as reverse causation could have influenced our results to some extent as it was not clear whether the FE got unfavorable before the ailment (thus playing etiologic role) or as a result of the ailment (reverse causation). Third, like any observational study, causal interpretations of the observed results are not recommended. Fourth, owing to the hospital-based selection of cases and neighborhood-based selection of controls, selection bias and generalizability issues were there. Although keeping the clearly identified catchment area of the hospitals under the study and excellent participation rate of the approached individuals in mind, we considered these issues to be of relatively smaller magnitude. Still, the result of our study should be extrapolated beyond the study sample with caution.
Despite these limitations by virtue of relatively large number of schizophrenia case, robust methodology of the study, quality of the tools used, and strength of the data analyses, we believe that this study could generate important insight for the psychiatrists, psychologists, public health researchers, and policymakers, into an important yet understudied aspect regarding this debilitating disease.
The findings of this study, especially those regarding the contribution of the components of the FE in increasing (e.g., conflict) or diminishing (e.g., active recreational orientation) the risk of schizophrenia pathogenesis, need to be conveyed appropriately to the mental health program designers and policymakers for appropriate translation into family-level intervention designing so that vulnerable families can be intervened appropriately in due course of time, to minimize the burden of this menace in the community. Psychiatric social workers and nurses can be trained appropriately to keep the FE in mind, while dealing with the schizophrenia patients, identify issues and intervene appropriately.
Future research endeavors on schizophrenia, being informed by the study findings, need to conduct further investigations regarding the analyses of the pathways to determine how the domains of FE interact with the mental architecture of the family members and could potentially culminate into the disease. Prospective investigations are also required to better understand the pathogenesis in which sociodemographic strata remain more vulnerable for those identified pathways of disease progression.
| Conclusion|| |
All the subdomains of FE cumulatively measured the potential for FE to culminate into a comprehensive influence on the mental conditions of the family members. This seemed extremely important in the pathogenesis of schizophrenia. Our results indicated that conflict was positively and most of the other subdomains of FE were negatively associated with the risk of schizophrenia development. Some of the subdomains such as active-recreational orientation were also important for the prognosis of the disease. Urgent family-level interventions, especially targeting the nuclear families, married, and less educated individuals, those belonging to both ends of the socioeconomic spectrum and urban residents, to generate awareness regarding the adverse effects of poor FE and to prevent ailments such as schizophrenia by improvement of the FE seemed to be the need of the hour.
The authors are thankful to Dr. Prakash Narayan Shukla, director, PGIBAMS, Raipur, and Dr. Pramod Gupta, director, CIMHANS, Durg, for their kind cooperation and guidance.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Repetti RL, Taylor SE, Seeman TE. Risky families: Family social environments and the mental and physical health of offspring. Psychol Bull 2002;128:330-66.
Bergman AJ, Wolfson MA, Walker EF. Neuromotor functioning and behavior problems in children at risk for psychopathology. J Abnorm Child Psychol 1997;25:229-37.
Parnas J, Teasdale TW, Schulsinger H. Institutional rearing and diagnostic outcome in children of schizophrenic mothers. A prospective high-risk study. Arch Gen Psychiatry 1985;42:762-9.
Schiffman J, LaBrie J, Carter J, Cannon T, Schulsinger F, Parnas J, et al.
Perception of parent-child relationships in high-risk families, and adult schizophrenia outcome of offspring. J Psychiatr Res 2002;36:41-7.
Rubin E. Zur verebune und neuenistehung der dementia praecox. Mongrafen. Berlin: Springer Verlag; 1916.
Patterson RM. Ordinal position in schizophrenia. Am J Psychiatry 1941;98:455-8.
Schuler EA. The family relationship of birth order and fraternal position to incidence of insanity. Am J Psychiatry 1930;36:28-40.
Fromm-Reichmann F. Notes on the development of treatment of schizophrenics by psychoanalytic psychotherapy. Psychiatry 1948;11:263-73.
Gerard DL, Siegel J. The family background of schizophrenia. Psychiatr Q 1950;24:47-73.
Prout CT, White MA. A controlled study of personality relationships in mothers of schizophrenic male patients. Am J Psychiatry 1950;107:251-6.
Tietze T. A study of mothers of schizophrenic patients. Psychiatry 1949;12:55-65.
Lidz TC, Cornelison A, Fleck S, Terry D. The intra familial environment of the schizophrenic patient: The father. Psychiatry 1957;20:329-32.
Lidz T, Cornelison AR, Fleck S, Terry D. The intra familial environment of schizophrenic patients. II. Marital schism and marital skew. Am J Psychiatry 1957;114:241-8.
Bagadia VN, Mundra VK, Shastri PG, Dave KP, Mankodia R, Shah LP. Schizophrenia: A study of the family and childhood environment in 495 cases from Bombay, India. Indian J Psychiatry 1979;21:101-5. [Full text]
Rastogi DS, Mahal AS. Patterns of family relationship in schizophrenia. Indian J Psychiatry 1971;13:209-17. [Full text]
Sen Majumdar DP, Sinha SK. An investigation to certain selected dynamic factors in paranoid schizophrenic subjects as compared to normal subjects. Indian J Psychiatry 1972;14:399-406.
Bateson G, Jackson DD, Haley J, Weakland J. Toward a theory of schizophrenia. Behav Sci 1956;1:251-4.
Wynne LC, Ryckoff IM, Day J, Hirsch SI. Pseudomutuality in the family relationships of schizophrenics. Psychiatry 1958;21:205-20.
Brown GW. Length of hospital stay and schizophrenia: A review of statistical studies. Acta Psychiatr Neurol Scand 1960;35:414-30.
Breitborde NJ, López SR, Nuechterlein KH. Expressed emotion, human agency, and schizophrenia: Toward a new model for the EE-relapse association. Cult Med Psychiatry 2009;33:41-60.
Brown GW, Birley JL, Wing JK. Influence of family life on the course of schizophrenic disorders: A replication. Br J Psychiatry 1972;121:241-58.
Hooley JM, Rosen LR, Richters JE. Expressed emotion: Towards the clarification of a critical construct. In: Miller GA, editor. The Behavioral High Risk Paradigm in Psychopathology. New York: Springer; 1995. p. 88-120.
Vaughn CE, Leff JP. The influence of family and social factors on the course of psychiatric illness. A comparison of schizophrenic and depressed neurotic patients. Br J Psychiatry 1976;129:125-37.
Hartwell CE. The schizophrenogenic mother concept in American psychiatry. Psychiatry 1996;59:274-97.
Caqueo-Urízar A, Rus-Calafell M, Urzúa A, Escudero J, Gutiérrez-Maldonado J. The role of family therapy in the management of schizophrenia: Challenges and solutions. Neuropsychiatr Dis Treat 2015;11:145-51.
Chakrabarti S, Raj L, Kulhara P, Avasthi A, Verma SK. Comparison of the extent and pattern of family burden in affective disorders and schizophrenia. Indian J Psychiatry 1995;37:105-12.
] [Full text]
Hogarty GE, Anderson CM, Reiss DJ, Kornblith SJ, Greenwald DP, Javna CD, et al.
Family psychoeducation, social skills training, and maintenance chemotherapy in the aftercare treatment of schizophrenia. I. One-year effects of a controlled study on relapse and expressed emotion. Arch Gen Psychiatry 1986;43:633-42.
Koujalgi SR, Patil SR. Family burden in patient with schizophrenia and depressive disorder: A comparative study. Indian J Psychol Med 2013;35:251-5.
] [Full text]
Goldstein MJ, Miklowitz DJ. The effectiveness of psychoeducational family therapy in the treatment of schizophrenic disorders. J Marital Fam Ther 1995;21:361-76.
Thomas JK, Suresh Kumar PN, Verma AN, Sinha VK, Andrade C. Psychosocial dysfunction and family burden in schizophrenia and obsessive compulsive disorder. Indian J Psychiatry 2004;46:238-43.
] [Full text]
Kulhara P, Shah R, Aarya KR. An overview of Indian research in schizophrenia. Indian J Psychiatry 2010;52:S159-72.
World Health Organization. The ICD-10 Classification of Mental and Behavioural Disorders: Clinical Descriptions and Diagnostic Guidelines. Geneva: World Health Organization; 1992.
Häfner H. Gender differences in schizophrenia. Psychoneuroendocrinology 2003;28:17-54.
Venkatesh BK, Thirthalli J, Naveen MN, Kishorekumar KV, Arunachala U, Venkatasubramanian G, et al
. Sex difference in age of onset of schizophrenia: Findings from a community-based study in India. World Psychiatry 2008;7:173-6.
Goldberg D. Manual of the General Health Questionnaire. Swindon (Wiltshire): NFER Nelson; 1978.
Bhatia H, Chadha N. Manual for Family Environment Scale. Lucknow: Ankur Psychological Agency; 1993.
Andreasen NC. Scale for the Assessment of Positive Symptoms (SAPS). Iowa City, IA: University of Iowa; 1984.
Andreasen NC. Scale for the Assessment of Negative Symptoms (SANS). Iowa City, IA: University of Iowa; 1983.
Loughland C, Draganic D, McCabe K, Richards J, Nasir A, Allen J, et al
. Australian schizophrenia research bank: A database of comprehensive clinical, endophenotypic and genetic data for aetiological studies of schizophrenia. Aust N
Z J Psychiatry 2010;44:1029-35.
Srivastava A. Marriage as a perceived panacea to mental illness in India: Reality check. Indian J Psychiatry 2013;55:S239-42.
] [Full text]
Isohanni I, Järvelin MR, Nieminen P, Jones P, Rantakallio P, Jokelainen J, et al.
School performance as a predictor of psychiatric hospitalization in adult life. A 28-year follow-up in the Northern Finland 1966 birth cohort. Psychol Med 1998;28:967-74.
Versola-Russo J. Cultural and demographic factors of schizophrenia. Int J Psychosoc Rehabil 2006;10:89-103.
Bresnahan M, Susser E. Investigating socioenvironmental influences in schizophrenia: Conceptual and design issues. In: Murray RM, Jones PB, Susser E, van Os J, Cannon M, editors. The Epidemiology of Schizophrenia. Cambridge: Cambridge University Press; 2003. p. 5-17.
McGrath J, Saha S, Welham J, El Saadi O, MacCauley C, Chant D, et al.
Asystematic review of the incidence of schizophrenia: The distribution of rates and the influence of sex, urbanicity, migrant status and methodology. BMC Med 2004;2:13.
Aleman A, Kahn RS, Selten JP. Sex differences in the risk of schizophrenia: Evidence from meta-analysis. Arch Gen Psychiatry 2003;60:565-71.
Boydell J, Murray R. Urbanization, migration and risk of schizophrenia. In: Murray RM, Jones PB, Susser E, van Os J, Cannon M, editors. The Epidemiology of Schizophrenia. Cambridge: Cambridge University Press; 2003. p. 49-70.
Di Forti M, Lappin JM, Murray RM. Risk factors for schizophrenia-all roads lead to dopamine. Eur Neuropsychopharmacol 2007;17:S101-7.
Frissen A, Lieverse R, Drukker M, Delespaul P, Lataster T, Myin-Germeys I, et al.
Evidence that childhood urban environment is associated with blunted stress reactivity across groups of patients with psychosis, relatives of patients and controls. Soc Psychiatry Psychiatr Epidemiol 2014;49:1579-87.
Mortensen PB, Pedersen CB, Westergaard T, Wohlfahrt J, Ewald H, Mors O, et al
. Effects of family history and place and season of birth on the risk of schizophrenia. N
Engl J Med 1999;340:603-8.
Weisman A, Rosales G, Kymalainen J, Armesto J. Ethnicity, family cohesion, religiosity and general emotional distress in patients with schizophrenia and their relatives. J Nerv Ment Dis 2005;193:359-68.
[Table 1], [Table 2], [Table 3], [Table 4]