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Ethnic Identity and the Risk of Schizophrenia in Ethnic Minorities: A Case-Control
Study
Wim Veling
1–3
, Hans W. Hoek
2,4,5
, Durk Wiersma
5
, and
Johan P. Mackenbach
3
2
Research Department, Parnassia Psychiatric Institute, The Hague,
The Netherlands;
3
Department of Public Health, Erasmus Medical
Centre,Rotterdam,The Netherlands;
4
DepartmentofEpidemiology,
Columbia University, New York, NY;
5
Department of Psychiatry,
University Medical Centre Groningen, Groningen, The Netherlands
Objectives: The high incidence of schizophrenia in immi-
grant ethnic groups in Western Europe may be explained
by social stress associated with ethnic minority status. Pos-
itiveidentificationwithone’s own ethnicgroupis a strongpre-
dictor of mental health in immigrants. We investigated
whether negative ethnic identity is related to schizophrenia
risk in non-Western immigrants. Methods: Matched case-
control study of first-episode schizophrenia, including 100
non-Western immigrant cases, general hospital controls
(n5100), and siblings (n563). Conditional logistic re-
gression analyses were used to investigate associations be-
tween schizophrenia and ethnic group identity. Results:
Cases had a negative ethnic identity more often than general
hospitalcontrols (64%and 35%, respectively, P<.001).After
adjustment for marital status, level of education, unemploy-
ment, self-esteem, social support, and cannabis use, negative
ethnic identity was associated with schizophrenia: odds
ratio 53.29; 95% confidence interval 51.36–7.92. Cases
significantly more often had an assimilated or a margin-
alized identity and less often had a separated identity.
Comparisons between cases and siblings largely confirmed
these findings. Conclusions: Negative identification with
the own ethnic group may be a risk factor for schizophrenia
in immigrants living in a context of social adversity.
Key words: identity/migrants/acculturation/psychosis
Introduction
The striking finding of a very high incidence of schizo-
phrenia and other psychotic disorders among ethnic mi-
nority groups in Western Europe
1,2
remains largely
unexplained. Reviews have suggested that adverse social
experiences of ethnic minority groups may contribute to
their elevated risk, such as perceptions of discrimination
and exclusion.
3
Few studies evaluated this hypothesis,
showing that ethnic minority groups’ experiences of dis-
crimination were associated with the incidence of schizo-
phrenia in these groups,
4
perceived disadvantage
compared with other individuals in society partially
explained the excess of psychosis among the UK black
population,
5
and the risk for psychotic disorders was par-
ticularly high for members from ethnic minority groups
living in neighborhoods where their own ethnic group
comprised a small proportion of the population.
6,7
The present study investigated how such adverse social
experiences would result in individuals developing
schizophrenia. We focused on ethnic group identity be-
cause positive identification with one’s own ethnic group
has been shown to buffer negative consequences of racial
discrimination
8
and is a strong predictor of mental health
in first- and second-generation immigrants.
9,10
Strong
orientation toward the own minority group may diminish
perceptions of exclusion and disadvantage,
11
whereas
a positive ethnic minority identity is likely to be threat-
ened in those who live isolated from their own ethnic
group.
12
A second dimension of ethnic group identity is the
identity as a member of the larger society (hereafter na-
tional or Dutch identity), which is independent of ethnic
minority identity (hereafter ethnic identity).
13
An individ-
ual who retains a strong ethnic identity while also iden-
tifying with the larger society is considered to have an
integrated identity. One who has a strong ethnic identity
but a weak national identity has a separated identity,
whereas one who gives up an ethnic identity and only
has a strong national identity has an assimilated identity.
The individual who identifies neither with the own ethnic
group nor with the larger society has a marginalized iden-
tity.
9
Of these 4 identity positions, integration has been
associated with good mental health,
9,14
and marginaliza-
tion has been shown consistently to predict low self-
esteem and poor mental health.
9,11
Research of health
consequences of separation and assimilation had contra-
dictory results depending on outcome and context.
15
1
To whom correspondence should be addressed; Center for Early
Psychosis, Parnassia Psychiatric Institute, Prinsegracht 63,
2512EX The Hague, The Netherlands; tel: þ31-70-391-7160, fax:
þ31-70-391-7088, e-mail: w.veling@parnassia.nl.
Schizophrenia Bulletin vol. 36 no. 6 pp. 1149–1156, 2010
doi:10.1093/schbul/sbp032
Advance Access publication on May 8, 2009
ÓThe Author 2009. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved.
For permissions, please email: journals.permissions@oxfordjournals.org.
1149
Given the pattern of a higher psychosis risk for second-
generation immigrants,
16
who are generally more assim-
ilated than immigrants of the first generation,
13
and
the findings of a lower risk for immigrants living in
high–ethnic density neighborhoods,
7
assimilation may
increase the risk of schizophrenia, and separation may
be protective.
This case-control study of first-episode schizophrenia
among non-Western ethnic minorities in The Hague, The
Netherlands, was designed to investigate associations be-
tween these factors and risk for schizophrenia. We hy-
pothesized that first- and second-generation ethnic
minorities who developed schizophrenia would identify
themselves less often and less positive with their own eth-
nic group than their siblings and nonpsychotic controls
and that they would more often have an assimilated or
marginalized identity and less often a separated or inte-
grated identity.
Methods
Classification of Ethnicity
We used the classification of ethnicity as defined by The
Netherlands’ Bureau of Statistics. If a citizen, or (one of)
his or her parents, was born abroad, he or she is assigned
to the group of people born in the same country. If the
parents were born in different foreign countries, the
country of birth of the mother determines the assignment
to a particular group.
Participants
Cases. All first- or second-generation immigrants from
non-Western countries (of which 85% from Surinam,
Morocco, Turkey, or The Netherlands Antilles), aged
18–54 years, who made first contact with a physician
in The Hague for a psychotic disorder and received a di-
agnosis of a schizophrenia-spectrum disorder (Diagnostic
and Statistical Manual of Mental Disorders [Fourth Edi-
tion]: schizophrenia, schizophreniform disorder, schizo-
affective disorder) between October 1, 2000, and July
1, 2005, were eligible for the study (n=150). Case-
finding procedures and diagnostic protocol of the study
have been described elsewhere.
16
If the patient had been
adopted as a child, he or she was excluded (n=4).
Controls. For each patient, 2 control subjects were
recruited, matched for 5-year age-group, sex, and ethnicity
(including generation). They were screened for psychotic
symptoms (see ‘‘Measures’’), and were excluded if these
were present (n=5).
The first control group was recruited among the gen-
eral ethnic minority population of The Hague. To min-
imize selection bias as a result of pathways to care, the
controls were selected from immigrants who made con-
tact with nonpsychiatric secondary health-care services.
Controls were recruited from the outpatient departments
of Internal Medicine and Surgery of a general hospital.
The reasons for making contact with these departments
differed widely and included lipoma or nevus (n=15),
fracture (n=8), contusion (n=11), hemorrhoids
(n=8), sinus pilonidalis (n=5), anal fissure (n=5), in-
flammatory bowel disease (n=5), diabetes mellitus
(n=5), and other, less frequent diagnoses (n=38).
The second control group consisted of siblings of the
patients in order to (partially) control for genetic factors
and to control implicitly for unmeasured shared socioen-
vironmental confounding factors. It was not always pos-
sible to match siblings on sex and age.
All participants gave written informed consent for the
study. The study was approved by the regional ethics
committee. Structured interviews were conducted by
a resident in psychiatry (W.V.) and 4 trained research
assistants. If participants did not speak Dutch sufficiently
(n=9), 3 trained research assistants, who were native
speakers in Turkish, Kurdish, Urdu, Arabic, or Berber,
conducted the interviews. Because we expected this in ad-
vance to concern only a small minority of the sample, we
neither developed nor maintained a protocol for transla-
tion and backtranslation of the questionnaires. Partici-
pants were instructed to answer according to their
experiences in the year before illness onset, but the date
of illness onset was not assessed in a systematic way.
Measures
Ethnic and National Identity. Measures were adapted
from the International Comparative Study of Ethnocul-
tural Youth (ICSEY), a study among more than 10 000
adolescents from 30 ethnic groups in 13 countries, which
included Surinamese, Turkish, and Antillean immi-
grants in The Netherlands.
14
Identity was assessed
with the ordinal ICSEY Scale of Ethnic and National
Identity. This is a 10-item version of the Multigroup
Ethnic Identity Measure,
17
with response options rang-
ing from ‘‘strongly disagree’’ (1) to ‘‘strongly agree’’ (5),
assessing ethnic and national affirmation, sense of be-
longing, and feelings about being group member. An ex-
ample is ‘‘Being part of ethnic culture is embarrassing to
me.’’ We not only used the total scores of the Ethnic and
National Identity subscales as continuous measures but
also calculated the median scores of the Ethnic and Na-
tional Identity Scales to use these as cutoff points to
classify participants as having a positive or a negative
identity.
Also, participants were assigned to different identity
categories. Participants who scored above the median
of both ethnic identity and national identity were classi-
fied as having an integrated identity. Those with a score
above the median of ethnic identity but below the median
of national identity had a separated identity; those with
a score below the median of ethnic identity but above the
median of national identity had an assimilated identity;
W. Veling et al.
1150
and those who had a score below the median of both
measures had a marginalized identity.
Psychotic Symptoms. In control subjects, the psychosis
section of the Composite International Diagnostic Inter-
view, version 2.1,
18
was administered.
Other Measures. Associations between ethnic identity,
national identity, and schizophrenia may be confounded
and mediated by a host of factors, several of which were
explored. Self-esteem was measured with the 15-item
Rosenberg Self-esteem Scale (example: ‘‘On the whole, I
am satisfied with myself’’)
19
; the 6-item ICSEY Mastery
Scale assessed locus of control (example: ‘‘When I make
plans, I feel certain that I can make them work’’)
14
; and
the 12-item Shortened Social Support Scale (example:
‘‘How often does someone shows interest in you?’’)
20
mea-
sured perceived social support. Also, lifetime use of canna-
bis was recorded. Use was defined as more than 5 times.
Information was noted on marital status (single or
else). Socioeconomic status was assessed with level of ed-
ucation (no or primary, secondary, or higher education),
employment status (unemployed or else), and parental
social class: father’s level of occupation (according to
the classification of The Netherlands’ Bureau of Statis-
tics) and father’s level of education (no or primary, sec-
ondary, or higher education).
Key Informants. For all participants, key informants
were asked to complete a short version of the structured
interview for their relatives, which included sociodemo-
graphic information, life events, language use, racial dis-
crimination, and social behavior.
Validity and Reliability of Measures. For each ICSEY
Scale, it has been shown that it measures the same psy-
chological construct in all ethnic groups, as all Tucker’s
u’s, a measure of agreement,
21
were 0.90 or higher.
14
The
measures have shown good to excellent internal reliability
as well (Cronbach a’s >.70). Cronbach a’s in our sample
were good to excellent for Mastery (.70), Ethnic Identity
(.81), National Identity (.82), Self-esteem (.83), and Per-
ceived Social Support (.85). In 2 subsamples, we investi-
gated interrater reliability (n=23; tested because the
scales were administered by the interviewer and not filled
out by the participant) and test-retest reliability after 1
week (n=24) of the scales, with intraclass coefficients
of .85–.99 and .63–.96, respectively.
Statistical Analysis
Stata version 9.2 was used for all statistical analyses. The
pairwise matched case-control design required condi-
tional (fixed-effects) logistic regression techniques. The
regression models were fitted stepwise. First, each vari-
able was entered separately in the model. Those variables
that differed significantly between cases and control
groups (with Pvalues <.10) were selected for further
analyses. Next, the continuous and dichotomous varia-
bles of ethnic identity and national identity as well as
the 4 identity types were included with all potential con-
founding and/or mediating variables. Comparisons were
made between cases and general hospital controls (100
pairs) and between cases and sibling controls (63 pairs).
Additional analyses addressed the issue of information
bias. Scale scores of participants were compared with the
scores provided by their key informants with use of con-
ditional logistic regression.
Results
Of the 146 patients who were eligible for the study, 2
patients had deceased before the present study was con-
ducted. Twenty-six patients could not be interviewed be-
cause they had remigrated to their home country (n=5),
they were too ill during the entire study period (n=8), or
there was no current address available (n=13). Of the
118 patients who were contacted, 18 refused to partici-
pate. Thus, 100 patients were interviewed. Of the 168 sub-
jects in the general hospital control group who were
matched to the schizophrenia patients, 4 subjects were
physically too ill to be interviewed, 1 was mentally hand-
icapped, 3 were excluded because they had a psychotic
disorder, and 60 refused to participate. For 15 patients,
there was no sibling available because all siblings were
too young or lived abroad, patients had no sibling, or
patients did not know their current address. Nine patients
refused permission to contact their siblings; 2 patients
only had a sibling who had psychotic symptoms. For 11
of the remaining 74 patients, the siblings refused to partic-
ipate. Thus, siblings of 63 patients could be interviewed.
Characteristics of the study sample are shown in table 1.
Compared with controls, cases more often had single
marital status, were more often unemployed, and had
a lower level of education.
Also, cases had lower self-esteem than general hospital
controls and siblings in the year before illness onset and
more often had a lifetime history of cannabis use.
Using the continuous measure, weak ethnic identity was
strongly associated with schizophrenia in the comparison
between cases and general hospital controls (odds ratio
[OR] =1.13, 95% confidence interval [CI] =1.06–1.21,
P<.001; adjusted OR =1.12, 95% CI =1.03–1.22, P=
.006). The difference in Negative Dutch Identity Scale
score between cases and controls was not statistically sig-
nificant (OR =1.00, 95% CI =0.92–1.08, P=.983; adjusted
OR =0.89, 95% CI =0.79–1.01, P=.062).
Using the dichotomous measure, cases more often had
a negative ethnic identity than general hospital controls
(64% and 35%, respectively, P<.001, table 2). A similar
proportion of the groups had a negative Dutch identity
(table 2). After adjustment for potential confounding
and/or mediating factors, negative ethnic identity was still
significantly associated with schizophrenia (OR =3.29,
1151
Ethnic Identity and Schizophrenia
95% CI =1.36–7.92) (table 3). Also, in the final model,
a negative Dutch identity was related to a lower risk for
schizophrenia (OR =0.36, 95% CI =0.15–0.87) (table 3).
The analyses of the identity types showed that cases sig-
nificantly more often had an assimilated or a marginalized
identity and less often had a separated identity (table 4).
In the comparison between cases and siblings, the con-
tinuous measure of negative ethnic identity was related to
a higher risk for schizophrenia (OR =1.22, 95% CI =
1.09–1.37, P=.001; adjusted OR =1.30, 95% CI =
1.04–1.62, P=.019). An increase in negative Dutch iden-
tity was not significantly associated with schizophrenia
(OR =0.92, 95% CI =0.83–1.03, P=.151; adjusted
OR =0.92, 95% CI =0.96–1.10, P=.345).
The dichotomous measure of negative ethnic identity
strongly predicted schizophrenia (adjusted OR =4.33,
95% CI =1.78–10.53), whereas negative Dutch identity
was associated with a lower risk of schizophrenia (OR =
0.19, 95% CI =0.07–0.55, table 3). After adjustment for po-
tential confounding and/or mediating factors, the OR for
negative ethnic identity increased but was not statistically
significant (P=.065). Negative Dutch identity remained
to be related to a lower risk for schizophrenia (table 3).
Finally, cases had significantly less often a separated
identity than their siblings (table 4). Information from
key informants was available for 43 cases, 38 siblings,
and 44 general hospital controls. There were no statistically
significant differences between the information from the
cases and from their key informants. In the sibling and in
the general hospital control groups, participants rated their
social integration somewhat higher than their key inform-
ants did (results not shown, available on request).
Table 1. Characteristics of Study Sample by Matched Case-Control Status
a
Cases (n=100)
General Hospital
Controls (n=100) Cases (n=63)
Sibling Controls
(n=63)
Age (y) 26.6 (6.7) 27.2 (7.2) 25.9 (6.8) 26.5 (8.5)
Male sex, n(%) 74 (74) 72 (72) 50 (79) 29 (46)
b
Ethnicity, n(%)
Moroccan 29 (29) 30 (30) 20 (32) 20 (32)
Turkish 19 (19) 20 (20) 12 (19) 12 (19)
Surinamese 32 (32) 34 (34) 21 (33) 21 (33)
Other non-Western 20 (20) 17 (17) 10 (16) 10 (16)
Second generation, n(%) 36 (36) 35 (35) 27 (43) 28 (44)
Single marital status, n(%) 72 (72) 46 (46)
b
52 (83) 37 (59)
b
Level of education, n(%)
No/primary 9 (9) 11 (11) 3 (5) 6 (10)
Secondary 77 (76) 63 (63) 48 (76) 37 (59)
Higher 13 (13) 26 (26) 11 (17) 20 (32)
Occupational level of
father, n(%)
c
Low 59 (63) 46 (58) 39 (64) 39 (65)
Middle 26 (28) 28 (35) 17 (28) 15 (25)
High 8 (9) 6 (8) 5 (8) 6 (10)
Level of education of
father, n(%)
d
No/primary 41 (57) 49 (62) 21 (47) 30 (56)
Secondary 25 (35) 22 (28) 19 (43) 18 (33)
Higher 6 (8) 8 (10) 4 (9) 6 (11)
Unemployed, n(%) 17 (17) 9 (9) 13 (21) 3 (5)
e
Cannabis use, n(%) 59 (59) 21 (21)
b
20 (32) 13 (21)
b
Self-esteem 53.68 (12.12) 60.28 (9.97)
b
53.65 (12.26) 61.52 (10.13)
b
Mastery 23.73 (5.21) 24.76 (4.30) 24.73 (4.56) 25.87 (3.66)
Perceived social support 27.95 (8.12) 33.80 (5.86)
b
28.71 (8.30) 31.10 (6.81)
a
Means (SDs), unless otherwise specified.
b
P<.005, Wald test, conditional logistic regression analysis.
c
Information missing for 31 (11.7%) participants.
d
Information missing for 59 (22.3%) participants.
e
P<.05, Wald test, conditional logistic regression analysis.
1152
W. Veling et al.
Discussion
In this case-control study of first-episode schizophrenia
among non-Western ethnic minorities, negative
identification with the own ethnic group was associated
with schizophrenia. Individuals who developed schizo-
phrenia identified themselves less positive with their
own ethnic group than general hospital controls in
the year before illness onset. There were no consistent
associations between negative Dutch identity and
schizophrenia risk, but cases had more often an assim-
ilated or a marginalized identity than the matched con-
trols and less often a separated identity.
Comparisons between cases and their siblings largely
confirmed these findings. Although this case-sibling de-
sign only partially controls for genetic factors, the simi-
larity of the results in the 2 control groups makes it
unlikely that genetic vulnerability for schizophrenia
can account for the findings.
These results are consistent with the hypothesis that
identification with the own ethnic group, but not identi-
fication with the majority group, may protect from
schizophrenia. Positive identification with the own ethnic
group is not intrinsically protective; however, its value
depends upon the social context. Belonging to an ethnic
minority group subjected to discrimination and negative
stereotyping has previously been associated with the in-
cidence of schizophrenia
4
and represents a threat to self-
esteem and social identity.
11
Individuals may respond to
this threat by asserting identification with their group and
Table 2. Measures of Identity and Risk for Schizophrenia by Matched Case-Control Status
a
Cases
(n=100)
General Hospital
Controls (n=100) OR (95% CI)
Cases
(n=63)
Sibling Controls
(n=63) OR (95% CI)
Negative ethnic
identity, n(%)
b
64 (64) 35 (35) 3.42 (1.80–6.50) 38 (60) 18 (29) 4.33 (1.78–10.53)
Negative Dutch
identity, n(%)
b
47 (47) 53 (53) 0.76 (0.42–1.38) 30 (48) 48 (76) 0.19 (0.07–0.55)
Note: OR, odds ratio; CI, confidence interval.
a
Differences between groups tested with Wald tests in conditional logistic regression analysis.
b
Median used as cutoff on scale scores of affective ethnic and Dutch identity.
Table 3. Effect of Potential Confounding/Mediating Factors in the Relationship Between Schizophrenia and Ethnic Minority/Dutch
Identity
a
Cases vs General Hospital Controls (100 Pairs) Cases vs Sibling Controls
b
(63 Pairs)
OR 95% CI POR 95% CI P
Negative ethnic
identity
Unadjusted 3.42 1.80–6.50 .000 4.26 1.57–11.54 .004
Adjustment for
Marital status 4.09 1.96–8.52 .000 4.72 1.52–14.62 .007
Level of education 3.69 1.89–7.21 .000 4.14 1.48–11.60 .007
Unemployment 3.64 1.86–7.09 .000 4.66 1.52–14.26 .007
Self-esteem 3.08 1.57–6.06 .001 2.47 0.81–7.50 .111
Social support 2.68 1.33–5.40 .006 4.28 1.47–12.53 .008
Cannabis use 3.05 1.58–5.88 .001 4.06 1.50–11.02 .006
All the above 3.29 1.36–7.92 .008 6.39 0.89–45.93 .065
Negative Dutch identity
Unadjusted 0.76 0.42–1.38 .367 0.23 0.07–0.74 .014
Adjustment for
Marital status 0.68 0.35–1.30 .239 0.16 0.04–0.61 .007
Level of education 0.78 0.43–1.44 .428 0.23 0.07–0.74 .013
Unemployment 0.68 0.36–1.26 .217 0.26 0.07–0.95 .042
Self-esteem 0.64 0.33–1.24 .183 0.20 0.05–0.75 .017
Social support 0.49 0.24–1.00 .050 0.21 0.06–0.71 .011
Cannabis use 0.76 0.40–1.44 .395 0.21 0.07–0.69 .010
All the above 0.36 0.15–0.87 .023 0.14 0.02–0.93 .042
Note: OR, odds ratio; CI, confidence interval.
a
Conditional logistic regression, differences tested for statistical significance with Wald tests.
b
All associations adjusted for sex because matching for sex was not always possible.
1153
Ethnic Identity and Schizophrenia
by seeking positive distinctiveness from the majority
group, which enhances self-esteem,
22
prevents or buffers
stress,
8
and has been associated with psychological well-
being
9,10
(an example of this strategy is the ‘‘Black is beau-
tiful’’ movement in the 1960s in the United States). An op-
posite response to this threat is trying to downplay ethnic
identity, striving to leave the low-status minority group
and to join the dominant group.
11
The boundaries be-
tween ethnic groups are difficult to cross, however, which
meansthatthis strategy often increasesratherthan resolves
the threat.
13
It is likely to be associated with feelings of hu-
miliation and with experiences of an undeserved gap be-
tween aspirations and achievements.
23
The social stress
resulting from this social defeat is a severe cognitive and
emotional challenge, which may exceed the coping ability
of individuals with a genetic vulnerability to schizophrenia,
who often have impaired executive function. When sub-
jected to such a severe challenge, they may be more likely
to develop the disorder.
23
Results from animal experiments
suggest that social stress may induce changes in the brain
that resemble those in schizophrenia. Repeated exposure
to social stress enhances the behavioral response of rats
to dopamine agonists and leads to mesolimbic dopami-
nergic hyperactivity,
24
which has been implicated in the
pathogenesis of schizophrenia.
25
Confounding and/or Mediating Factors
The effects of several social and psychological factors on
the associations between schizophrenia and identity were
investigated by adding these separately to the regression
model. The influence of ethnic identity on schizophrenia
risk was partly attenuated by cannabis use, self-esteem,
and perceived social support. Cannabis use may be a con-
founding as well as a mediating factor. It not only has
been related to the onset of schizophrenia
26
but may
also be a behavioral consequence of the social stress
of negative ethnic identity. Indeed, in our total sample,
cannabis use was correlated to negative affective ethnic
identity (r=.22, P<.005).
Lack of ethnic identification may also lead to social
isolation and less social support (correlation between
negative affective ethnic identity and social support: r=
.22, P<.005). Social support increases access to nor-
malizing explanations for anomalous perceptual experi-
ences and abnormal beliefs that are present in individuals
at high risk for developing psychosis.
27
Whereas social
isolation may contribute to the acceptance of a psychotic
appraisal of these early abnormal mental states, a social
network may have a normalizing function, thus prevent-
ing transition into psychosis.
28
Limitations
Several limitations are inherent to the case-control de-
sign. First, because the interviews were conducted
(shortly) after the first episode of schizophrenia, the
results may have been influenced by the illness. We
have tried to minimize this potential bias by instructing
the patients that the interview concerned the period be-
fore the onset of illness. Still, it is possible that (the early
stage of) the illness leads to negative feelings about being
ethnic and to more positive feelings about being Dutch,
for instance in patients who blame their problems to their
membership of an ethnic group or who feel rejected by
this group.
This issue of reverse causality also applies to the poten-
tial mediating factors. For instance, low social support
from family and other members of the own ethnic group
may lead to a weak and negative ethnic identity.
Second, it is difficult to assess experiences, behaviors,
and opinions accurately in retrospect. This applies to all
participants because we interviewed the controls on the
same time period as the case they were matched to,
but problems with recall are likely to be larger for cases
than for controls as a result of cognitive impairments
caused by the illness. Additional analyses showed that
there were no significant differences between scores of
cases and their key informants (available on request),
suggesting that recall bias cannot explain the results.
Table 4. ORs of Schizophrenia for Identity Types; Conditional Logistic Regression
Identity Type
a
Cases vs General Hospital Controls
b
Cases vs Sibling Controls
c
OR 95% CI POR 95% CI P
Integrated 0.54 0.26–1.11 .10 4.69 0.81–27.91 .09
Separated 0.17 0.06–0.47 .001 0.09 0.02–0.42 .002
Assimilated 4.68 1.82–12.04 .001 5.55 0.75–41.00 .09
Marginalized 2.28 1.06–4.91 .04 3.05 0.84–11.09 .09
Note: OR, odds ratio; CI, confidence interval.
a
Median used as cutoff on scale scores of affective ethnic and Dutch identity. Integrated identity indicates high ethnic and high Dutch
identity, separated is high ethnic and low Dutch identity, assimilated is low ethnic and high Dutch identity, marginalized is low ethnic
and low Dutch identity.
b
One hundred pairs, associations adjusted for marital status, level of education, and unemployment.
c
Sixty-three pairs, associations adjusted for sex, marital status, level of education, and unemployment.
1154
W. Veling et al.
The sample size was relatively small. Comparisons be-
tween cases and siblings may have been underpowered
because only 63 siblings participated, and the matched
case-control design required conditional analyses. This
had large consequences for the statistical power, as the
pairwise analysis implied that the data of 37 cases could
not be used in these comparisons.
All consecutive first-episode schizophrenia cases be-
tween 2000 and 2005 were eligible for the study, but
not all patients participated. It is conceivable that those
individuals who were oriented more toward their own
ethnic group lost contact with psychiatric services in
the early phase of treatment or that they refused to par-
ticipate. However, the same selection bias would occur in
the control groups.
The general hospital controls may not have been rep-
resentative for the general immigrant population, but
the choice for a control group selected from immigrants
who made contact with nonpsychiatric secondary
health-care services reduced selection bias as a result
of pathways to care, as the schizophrenia cases were
also recruited from secondary psychiatric services. Still,
it may be argued that immigrants who seek help for their
physical health problems have a more positive attitude
toward Dutch society than schizophrenia patients,
a proportion of whom has been compelled into contact
with mental health services. This type of bias would lead
to an underestimation of the effect of negative ethnic
identity.
In addition, the very diverse complaints for which the
controls made contact make it very unlikely that their so-
matic illness would be related to ethnic identity.
We had also included the ICSEY measures of accultur-
ation strategies in the study,
14
measuring preference for
assimilation, integration, separation, and marginaliza-
tion in 5 domains of life: cultural traditions, language,
marriage, social activities, and friends. The scales, how-
ever, had low Cronbach a’s in our study sample (.34–.58),
indicating that these measures were not very reliable.
Therefore, we did not report the results in the main anal-
yses, although the results support the other findings, as
cases had significantly higher scores on assimilation
and marginalization than both control groups (results
available on request).
Previous Findings
These results are consistent with reports of a higher inci-
dence of schizophrenia among ethnic minorities living in
neighborhoods where their own ethnic group comprises
a small proportion of the population.
6,7
Those who live
in low–ethnic density neighborhoods must contend with
the triple burden of increased exposure to prejudice, re-
duced social support, and fewer possibilities for positive
ethnic identification,
12
factors that are likely to increase
the social stress of minority status.
Previous studies have found variable and modest asso-
ciations of low family socioeconomic status and incidence
of schizophrenia
29
and have suggested that socioeco-
nomic disadvantage may contribute to the increased in-
cidence among immigrants.
30
In our data, there were no
significant differences in parental socioeconomic status
between the groups, but it was very low in all groups.
Low socioeconomic status may represent a situation of
social exclusion,
29
particularly for individuals who com-
pare themselves predominantly with the advantaged ma-
jority group.
11,13
Conclusions
This study is the first to investigate associations between
ethnic/national identity and schizophrenia in ethnic mi-
norities and found that negative ethnic identity may be
related to schizophrenia risk. These results should be
interpreted with caution, given the complexity of the con-
cepts, the inherent difficulties in measuring these, and the
methodological limitations of the case-control design.
Future research might include identity measures in stud-
ies among high-risk individuals in order to investigate
whether weak ethnic identity predicts transition into psy-
chosis. If weak ethnic identity is a risk factor for schizo-
phrenia, preventive interventions may be developed to
empower young members from ethnic minority groups.
Funding
The Netherlands Organization for Health Research and
Development (100-002-009).
Acknowledgments
Declaration of interest: None. Use of the ICSEY
questionnaires by courtesy of the ICSEY research
group. We thank Han Entzinger, professor of Migration
and Integration Studies, Faculty of Social Sciences,
Erasmus University Rotterdam, for his comments on
a previous version of this article.
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