Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht
Department of Psychiatry, University Medical Center, Utrecht
Julius Center for Helath Sciences and Primary Care, University Medical Center, Utrecht, The Netherlands
Correspondence: Dr Huibert Burger, Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, PO Box 85500, 3508 GA, Utrecht, The Netherlands.Tel: +3130 250 7280; fax: fax: +31 30 250 5480; e-mail: H.Burger{at}umcutrecht.nl
ABSTRACT
A cross-sectional study of 3426 referred children and adolescents showed that the presence of both migration history and family dysfunction was associated with a fourfold (95% CI 29) higher risk of psychotic symptoms compared with the absence of these factors. The relative risk was 2 (95% CI 14) for migration history only. Interaction between migration history and family dysfunction accounted for 58% (95% CI 591%) of those with psychotic symptoms. These results suggest a relationship between family dysfunction and migration in the development of psychosis.
The association between migration history and psychotic disorders has been demonstrated repeatedly, but there has been no satisfactory explanation to date (Cantor-Graae et al, 2003). As seen in AfricanCaribbean immigrants to the UK, the effect of migration may depend on socioenvironmental variables (Mallett et al, 2002). We investigated whether the relationship between migration history and psychosis is modified by family dysfunction in a sample of children and adolescents referred to a tertiary mental healthcare centre.
METHOD
Between 1982 and 1998, a total of 5253 patients aged 618 years were evaluated at the Child and Adolescent Department of the University Medical Center Utrecht, The Netherlands. From these, an unselected sample of 3426 patients were assessed with the Maudsley Child and Adolescent Psychiatric Rating Scale, a semi-structured psychiatric interview (Thorley, 1982). There were 86 children and adolescents who definitely had hallucinations, delusions, ideas of reference or morbid ideas of persecution. This corresponds to a state of psychosis or probable psychosis. The interviews were performed by trainees in child and adolescent psychiatry who were supervised by board-certified specialists. Patients with symptoms of organic origin were excluded (n=4).
Migration history was defined as foreign birth (first generation) or foreign birth of at least one parent (second generation). In total 404 migrants (239 of the first generation) were identified.
Family dysfunction was recorded when at least three of the following seven problems were reported: poor relationship between adults in the household; lack of warmth between parents and child; overt disturbance of fatherchild relationship; overt disturbance of motherchild relationship; overt disturbance of siblingchild relationship; parental overprotection; and child abuse.
Relative risks of psychotic symptoms for individuals with a history of migration were quantified using logistic regression (Statistical Package for the Social Sciences, version 11.0 for Windows) and were expressed as odds ratios with 95% confidence intervals. Age, gender, psychiatric illness in at least one of the parents and educational level of the breadwinner (usually the father) were considered potential confounding variables. To determine whether the relationship between migration history and psychosis is modified by family dysfunction, the study population was divided according to family dysfunction and the analyses were repeated. Modification was quantified by calculating the interaction between these variables according to Rothman (1986). Corresponding 95% confidence intervals were calculated by boot-strapping as described by Assmann et al (1996).
RESULTS
Characteristics of the study population
In those with and without a migration history, the frequencies of family
dysfunction were 56% and 52%, the frequencies of psychiatric illness in a
parent were 22% and 25%, the proportions of parents that were university
graduates were 37% and 28% and the proportions that did not complete formal
education were 13% and 8%, respectively.
Migration as a risk factor for psychotic symptoms
Table 1 summarises the
results. Overall, migration was associated with an approximately twofold
increased risk of psychotic symptoms. When family dysfunction was absent, this
increase was substantially lower and no longer statistically significant,
indicating a lack of independence of the effects of migration and family
dysfunction. Adjustment for confounding variables did not substantially change
the results.
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To quantify the interaction between family dysfunction and migration, relative risks were calculated for exposure to both migration and family dysfunction, to family dysfunction only and to migration only, with no migration and no family dysfunction as the reference. The effect when both variables were present was larger than the sum of their independent effects, indicating causal interaction. The proportion of cases attributable to the interaction between migration history and family dysfunction was 58%.
DISCUSSION
Summary of findings
The relationship between migration and psychotic symptoms was considerably
stronger for children and adolescents from dysfunctional families than for
those who did not report family dysfunction. The interaction between migration
and family dysfunction accounted for the majority of individuals with
psychotic symptoms. The relationships were independent of age, gender, the
presence of psychiatric illness in the parents and the educational level of
the breadwinner.
Interpretation
In the current study, family dysfunction may have acted as a psychosocial
stressor upon susceptible individuals (i.e. those with a history of
migration), thus precipitating psychotic symptoms. This is in agreement with
findings from the Finnish Adoptive Family Study of Schizophrenia
(Wahlberg et al, 1997;
Tienari et al, 2004),
which demonstrate that susceptible individuals, in this study who adopted
children born to a biological mother with schizophrenia, are more sensitive to
the effects of an adverse family environment. Our results support the
hypothesis that the psychosocial environment plays a role in the increased
incidence of psychotic disorders in subjects with a history of migration
(Mallett et al,
2002).
Study limitations
Since family dysfunction and psychotic symptoms were measured
simultaneously, it is possible that family dysfunction was a result of the
psychotic symptoms rather than its cause. A second limitation is the
definition of psychosis. Patients were categorised according to the presence
of probable or definite psychotic symptoms, and not DSMIV or
ICD10 categories. However, this is in accordance with the evidence that
the boundaries of the psychosis phenotype extend beyond the clinical concept
of a psychotic disorder (van Os et
al, 2000). Importantly, psychotic symptoms in childhood and
adolescence are often followed by psychotic disorders in adult life
(Yung et al,
1998).
Third, the educational level of the breadwinner is not a reliable indicator of socio-economic status. Current evidence, however, increasingly indicates that the risk for schizophrenia is not associated with parental socio-economic status (Byrne et al, 2004). Finally, information bias and referral bias have to be considered. Information bias can only explain the interaction observed if the interviewers systematically scored family dysfunction more frequently in migrant patients than in non-migrant patients, and if this occurred specifically in patients with psychotic symptoms. Likewise, referral bias can only explain our results if referral of subjects from dysfunctional families was more likely for migrants than for nonmigrants, and if this applied specifically to psychotic symptoms. Hence, we regard information and referral bias as unlikely explanations of our results. However, the findings of this cross-sectional study need confirmation in longitudinal population-based studies.
In conclusion, in children and adolescents the increased risk of psychotic symptoms associated with a history of migration is considerably larger in the presence of family dysfunction. This suggests that migration history and family dysfunction act in a synergistic manner. Psychosocial stress associated with family dysfunction may contribute to the development of psychosis in migrants.
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Received for publication July 12, 2004. Revision received November 16, 2004. Accepted for publication November 20, 2004.
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