If madness is as old as humankind is, we might be tempted to assume that schizophrenia, one of today’s best known, most common, and most recognised forms of madness, has been present since the dawn of civilization. (Gottesman... 91. P.1). Surprisingly to the contrary, it has been argued that to search the centuries for schizophrenia is a valueless task, because schizophrenia is of recent origin. (Howell.91.p.10). Supporting this Torrey cited in Howell asserts, “There are no descriptions of schizophrenia, as we know it, before the early 19th century when Halsen in England and Pinel in France gave clear descriptions” (93.p.10). At this juncture, it is pertinent to note as Cromwell, informs, “the term “schizophrenic psychosis” by way of Eugene Bleuler’s writings” is enveloped with all the elements of our language, embedded in our consciousness with all the cultural influences that reflect the times. (93.p3.)

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PreamblePreamble
§
If madness is as old as humankind is, we might be tempted to assume that
schizophrenia, one of today’s best known, most common, and most
recognised forms of madness, has been present since the dawn of civilization.
(Gottesman... 91. P.1).
Surprisingly to the contrary, it has been argued that to search the centuries
for schizophrenia is a valueless task, because schizophrenia is of recent
origin. (Howell.91.p.10).
Supporting this Torrey cited in Howell asserts, “There are no descriptions of
schizophrenia, as we know it, before the early 19th century when Halsen in
England and Pinel in France gave clear descriptions” (93.p.10).
At this juncture, it is pertinent to note as Cromwell, informs, “the term
“schizophrenic psychosis” by way of Eugene Bleuler’s writings” is enveloped
with all the elements of our language, embedded in our consciousness with
all the cultural influences that reflect the times. (93.p3.)
-What then is schizophrenia-?
By way of explanations this paper will attempt to bring to light the above question
through explanation of the reasoning behind twin studies in the genetic versus
environmental contributions to abnormal behaviour ;focussing on research in the often
misunderstood and misrepresented malady of the modern human condition; that being
schizophrenia.
§
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This paper will give clear explanation of the rationale of twin studies in
schizophrenia.
It will demonstrate central issues, being why twin studies are relevant
and not so relevant to the contributions twin studies make in the
determinations of the genetic and environmental make up of abnormal
behaviour in schizophrenia.
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This is to be achieved through facilitating examples of the
conundrums linked and associated with twin study investigations of
schizophrenia, and, how genetic and environmental contributions
impact positively and not so positively in the pursuit of scientific
understanding of schizophrenia per se.
Defining facets of this paper will be frame worked by the above, and
described by two main elements.
First, how one defines schizophrenia vis a vis diagnostics, and
secondly but not insignificant to the previous element; so scribed’ and
most integral to the whole concept as presented above ,the effects
upon a person(s) experiencing living day to day, year by year with
schizophrenia, particularly with respect to women and schizophrenia.
†
The aetiology of major mental disorders involves a complex interplay of
nature and nurture.
Ridley.M.2007 cited in Roberts .S.S .et al p.97 argues, “Simplistic
nature nurture arguments are no longer tenable; especially, when
nurture is limited to the post uterine environments”.
Schizophrenia is for so many afflicted a chronic relapsing and
remitting condition that “affects approximately 1% of the world’s
populations”. (The Neurophysiology of Schizophrenia. 2003), (Mowry,
Nancarrow.2001),(Gottesman and Shields.82.p.113),and(Portin and
Alanen.97.p1)
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Interestingly it is also been demonstrated that schizophrenia occurs,
“across all socio-economic groups with recent evidence of an urban/
rural gradient reported”.
(Mortensen PB, Pedersen, CB, Westergard T. et al, cited in, Mowry
and Nancarrow .2001)
Mowry and Nancarrow reiterate, “while causes for schizophrenia
remain unknown, evidence from family, twin and adoption studies
clearly demonstrate that it aggregates in families”(2001).
Further to this, Mowry and Nancarrow assert this clustering can be
largely, “attributable to genetic rather than cultural and
environmental factors”. (2001).
With respect to familiality these same authors argue that twin studies
have shown that this familiality is predominantly genetic (vs.
cultural/environmental) factors. (Mowry and Nancarrow.2001).
With respect to genetics and twin studies into schizophrenia: Tsuang,
Gilbertson, and Faraone 91, and Risch 90; cited in Mowry and
Nancarrow 2001; highlight that concept by stating. “The prevalence of
schizophrenia in offspring is approximately 8%; (there is a high 50%
or more monozygotic concordance rate), suggesting the involvement of
multiple genes”. (2001)
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Contra to this hypothesis it is significant to note Portin and Alanens
perspective on genetic versus environment causality.
Basing there findings on the Finland twin studies, they assert,
“simple genetic hypothesis are not valid where schizophrenia is
concerned”. (1997.p.1). Accordingly; Portin and Alanens conflicting
evidence as to the proportion of the genetic component apparent in
the Scandinavian studies; in particular Danish and Finland twin
studies into schizophrenia, highlights yet another conundrum. Most
notably,and in relation to the Finland study where researcher Pekka
Tienare reported a 0% concordance rate in identical twins, in respect
to schizophrenia. These studies were, as Gottesman and Shields
poignantly point out, were carried out on one or both, and male
twins only. (82.p102); and what is most noteworthy; “half the
starting sample of 3.000 pairs were lost by age 16 by death (ordinary
and war related), in one or both pairs”. (Gottesman and
Shields.82.p102).
Intervening literature and contradictory opinions on the causal factors
in schizophrenia has significance; at this point of the argument; and,
it is of interest to note, that some people will argue that family
environment, rather than families’ genes accounts in relation to the
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5. twin concordance and discordance findings in relation to
schizophrenia.
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Gottesman and Shields contend in relation to the genetic/
environmental conundrum argues.
To disprove the genetic hypothesis it would be necessary to
show samples known to differ genetically such as MZ and DZ
co-twins of schizophrenics(100% vs.50% gene overlap) do not
differ in their rates of schizophrenia when exposed to the same
environments”.(82.p101).
Gottesman and Shields further this by highlighting
The nature of shared environments for parent-offspring
pairs is quite different from that shared by two siblings,
yet the risk of schizophrenia is the same ,as is the degree
of genetic relatedness”(82.p.101).
Gottesman and Shields analysis of older and more recent twin studies
in schizophrenia highlights the significance of meshing; maintaining
and comparing studies; the statistical processes used; and analysing
comparative summaries of concordance and discordance in
schizophrenic twin studies, so as one can proffer a balanced viewpoint
in respect to the genetic vis a vis environmental elements.
Gottesman and Shields report;
The rates reported in the older studies are simple pairwise ones;
they are less satisfactory than proband rates for comparison
with the risks reported for other relatives and for the general
population. (82.p102)
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6. † Note: (See appendix for tables 6.1, and table 6.2 concordance
rates in older and newer schizophrenic twin series).
With respect to concordance rates and diagnostic measures,
Gottesman and Shields, also express concerns in having concordance
rates too broad or too narrow in orientation to the diagnosis of
schizophrenia. (82.p111)
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These authors state in fact that:
Extremes eroded the MZ: DZ contrasts: sample size
unmercifully: too broad raised both the MZ and DZ rates to
dilute an indicator of “biological specificity”, the ratio of the
rates. (Gottessman and Shields .82.p.111.).
† Note See appendix (Refer to table 6.3 “possible reasons for the
magnitude of MZ concordance rates, for confounding element
summary).
Newer twin studies of schizophrenia have addressed such confounding
elements as so described above, through processes of: using proband
rates method; also, through using “more thorough sample
investigation; or, longer follow up times since the first published
results”. (ibid).
This therefore, resulting in; “No bizarre findings of MZ rates of 0%, a
result incompatible with either genetical or environmental arguments”
(Gottesman and Shields .82.p.112).
Regarding diagnostic issues in these twin studies, these were
addressed; as well as confirmed using a diagnostic criterion cut off
that was similar as possible to the consensus diagnosis formed in
Gottessman’s Maudsley twin study. (Gotesman and Shields.82p.112).
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In relation to discordant monozygotic twins, a further conundrum is
apparent.
Gottesman and Bertelsen .89;cited in Portin and Alanen, found “no
difference between the prevalence of schizophrenia in the children of
the sick twin (16.8%), and the offspring of the twin who remained
healthy”. (97.p .2).
However comparative studies (using pairwise methodologies), reported
a completely contradictory result to this end “the sample 17.9% of the
children of the sick twin were ill, compared to only 4.4% of the
offspring of the healthy twin”. (Klinglen and Kramer cited in Portin
and Alanen .97.p2).
As noted by Portin and Alanen in relation to this “the difference did
not reach the level of statistical significance ;however these
contradicting findings again indicate the problems encountered in
genetic studies of schizophrenia”(97.p.2).
Just reiterating ,and, as noted on page one of this paper ,multiple
authors postulate that the lifetime prevalence of schizophrenia in the
adult population ,regardless of race or country is about 1%,(and
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8. furthermore), in the siblings of patients it is 8-10%,and in children of
patients it is 12-15%.(Gottesman .93.cited,in Portin & Alanen 97.p.1.)
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It can therefore be assumed, that such insufficiencies of the strength
of genetic evidence, must lead to the assumption “that environmental
factors also play a role in the aetiology of schizophrenia” .(Portin and
Alanen 97.p.1).
♠
The methodological conundrum of genetically grounded evidence also
exists in relation to gender and twin studies of schizophrenia;
especially so in relation to older studies: these were as ,Gottesman
and Shields argue, “unbalanced in this regard”. (82.112).
In relation to gender differences, a similar conundrum of methodology
exists; Gottesman and Shields argue; in relation to concordance.
Female twin pairs tend to be concordant more often than male twin
pairs, and that of two of the recent studies, those with the lowest rate
of concordance only sampled male twin pairs. (Gottesman and Shields
.82.p.113).
Authors Gottesman and Shields believe that a complete evaluation of
this source of variation is onerous because its source of variation has
been closely linked “with other problems of sampling such as
chronicity of illness. (82.p114).
These authors stated preferred reason in relation to the older studies
in relation to concordance and chronicity as follows.
…Higher MZ concordance rates in the earlier studies is those
samples ,unlike the recent ones ,were heavily weighted with
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9. chronic unremitting cases of schizophrenia; such cases are
much more likely than others to have schizophrenic partners
(Gottesman, and Shields. 82. P.114).
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† Note (see appendix for table 6.4 sex sampling and concordance).
The concordance rates as so described and processed in table 6.4 sex
sampling and concordance, show there is:
No sex differences in concordance for schizophrenia and no
difference in the representation by sex …the higher concordance
in females is accounted for entirely by the use of samples with
biases –(interestingly)- through the loss of certain cases.
(Gottesman and Shields .82.p.114).
Furthermore evidence to the fact that with opposite –sex twins, when
studied, are no less concordant than same –sex fraternal twin pairs
further reinforces the aforementioned explanations.(Gottesman and
Shields .82.114.).
Furthermore as noted historically, gender differences in schizophrenia
have been confirmed by such empirical data as mentioned above, this
being so since the turn the 20th
century. However also of note is that
the study of schizophrenia has remained largely “gender blind”.
(Jarboe .98.p.4).
Clearly, there is a great deal of work to be achieved in the area of
studying women suffering from schizophrenia.
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The complexity of the research approaches necessary to explore the
area of gender differences in schizophrenia is immense, and may
explain the aforementioned conundrums as highlighted in this paper
as so found in research methodologies; therefore highlighting some of
the obstacles to the systematic study of gender differences and
specifically women suffering from schizophrenia .
It can again be postulated, from everything mentioned prior, that such
“insufficiencies” of the strength of genetic evidence, must lead to the
assumption “that environmental factors also play a role in the
aetiology of schizophrenia”. (Portin and Alanen 97.p.1).
This paper will now address the relevance that twin studies have; in
their contributions to women presenting with a diagnostic condition of
schizophrenia.
That being ,the realm of the environmental elements inherent to the
aetiology of schizophrenia twin studies, and its association with
epidemiological elements of; gender –based research, and
consequences for the person; that being a woman so diagnosed with
schizophrenia.
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11. Although gender-based research into schizophrenia has been lacking,
Jarboe argues,
Much of the credit for encouraging examination of this issue belongs -
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to epidemiologists who have described significant differences in the
age of onset, course and outcome of schizophrenia found between men
and women with schizophrenia. (98.p.5)
† Note (see appendix namely Table one: Gender differences in
Schizophrenia.).
With respect to table one; Gender differences in Schizophrenia, Jarboe
states, “these findings suggest a better outcome for women with
schizophrenia “(98.p.6)-(in comparison to male health outcomes).
However as Milburn and D’Ercole 91 cited in Jarboe illustrate ,
..There is evidence to suggest that women who fail to make a
good recovery have outcomes worse than men in the same
situation. Homelessness, poverty and victimization have a
greater subjective impact on a psychotic woman’s quality of life
than a man’s. (98.p.6).
Additionally relevant to the above facets Walter and Kenward
cited in Jarboe, concur as well that relating to women who are
chronically unwell with schizophrenia, they are at a very
heightened risk of, “domestic conflicts or abusive behaviours
from family members and thus increases the risk of
homelessness. (Jarboe .98.p6.).
By way of extrapolations into the above issues the above might
help clarify why researchers have met with difficulties as noted
in twin studies research, a major obstacle in statistical
methodologies as these authors believe: the chronicity of
illness contribution and concordance rates per se as
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12. “unbalanced in this regard’ (Gottesman and Shields.82.p113).
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Hence: this conundrum, is noted as being specific ,and,
“peculiar” to female twin studies, as so presented, within this
paper.
A further conundrum of the complexities inherent in schizophrenia:
and perhaps closely tied in with diagnostics per se; in relation to twin
studies and the environmental /genetic components per se, has
been in the pursuit of the scientific understanding of this disease.
This being from the standpoint of Neuro developmental theories.
Neurodevelopment theories extracted partly from studies of twins in
Schizophrenia attempt to build on epidemiological gender differences,
however as noted by Jarboe, “these theories do not explain the excess
of female patients presenting with their first episode of schizophrenia
in their late 20s and 30s”. (98.p.8.).
The above poses an important question relating to the efficacy of twin
study research, particularly regarding the more “classic” studies of the
early 20th
century, and women’s experiences of schizophrenia from
that time onward, in relation to the developing field euro-
developmental and its’ linkages to schizophrenia.
With resect to longitudinal designs and diagnostic methodology as has
been mentioned previously by Gottesman and Shields ,the newer twin
studies of schizophrenia are attempting to address such confounding
elements as onset and course of schizophrenia, by having longer
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13. follow -up times since the first published results, and more thorough
sample investigation”(82.p.111.) Created by Anne Percy
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Nasralla, 93, cited in Jarboe .98, argues that “Neurodevelopment in
women with schizophrenia may be under genetic control whereas;
neurodevelopment in men with schizophrenia appears to be mediated
by adverse environmental factors” (98.p.7.).
Further more and in relation to the above statements, Nasrallah and
Wilcox cited in Jarboe report,
Males are more prone to neurological brain insult as a result of
obstetrical complications, they have been reported to have a greater
incidence of structural brain pathologies than women.
(Jarboe.98.p.7.).
Twin studies have illustrated that foetal hypoxia and low birth weight
have been correlated, with an early onset of schizophrenia.
(Jarboe..89.p.7).
Further to this, some research has demonstrated that “females are at
decreased risk of neuro-developmental disorders when compared to
men” (Jarboe.89.p7.)
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