Ilpo Lahti

Thought disorder index of Finnish adoptees and communication deviance of their adoptive parents.

BACKGROUND Diverse forms of thought disorder, as measured by the Thought Disorder Index (TDI), are found in many conditions other than schizophrenia. Certain thought disorder categories are primarily manifest during psychotic schizophrenic episodes. The present study examined whether forms of thought disorder qualify as trait indicators of vulnerability to schizophrenia in persons who are not clinically ill, and whether these features could be linked to genetic or environmental risk or to genotype-environment interactions. The Finnish Adoptive Study of Schizophrenia provided an opportunity to disentangle these issues. METHODS Rorschach records of Finnish adoptees at genetic high risk but without schizophrenia-related clinical diagnoses (N = 56) and control adoptees at low genetic risk (N = 95) were blindly and reliably scored for the Thought Disorder Index (TDI). Communication deviance (CD), a measure of the rearing environment, was independently obtained from the adoptive parents. RESULTS The differences in total TDI between high-risk and control adoptees were not statistically significant. However, TDI subscales for Fluid Thinking and Idiosyncratic Verbalization were more frequent in high-risk adoptees. When Rorschach CD of the adoptive rearing parents was introduced as a continuous predictor variable, the odds ratio for the Idiosyncratic Verbalization component of the TDI of the high-risk adoptees was significantly higher than for the control adoptees. CONCLUSIONS Specific categories of subsyndromal thought disorder appear to qualify as vulnerability indicators for schizophrenia. Genetic risk and rearing-parent communication patterns significantly interact as a joint effect that differentiates adopted-away offspring of schizophrenic mothers from control adopted-away offspring.

Interaction of Genetic and Psychosocial Factors in Schizophrenia

What the genetic and family dynamic theory have in common, is that the cause of schizophrenia could be found in the family. Usually the genetic factors and the rearing factors are confounded in the same family. In a study of adoptive children given away for adoption early enough, discrimination between these two sets of factors is possible.

Genotype-environment interaction in the Finnish adoptive family study — Interplay between genes and environment?

Nature and nurture are not separate. Instead of studying them apart from each other, it is important to investigate the interplay between genes and environment and how they influence one another. To an important degree, genetic effects on behavior come about because they either influence the extent to which the individual is likely to be exposed to individual differences in environmental risk or they affect how susceptible the individual is to environmental adversities [17]. The disorders of greatest medical, research, and policy concern today, particularly in psychiatry, are likely to be complex. Such disorders may have not a single cause but a causal chain, or multiple such chains. These chains may involve genetic, biological, environmental and social risk factors. The effect of a single risk factor can only be fully understood in the context of all the others [7].

Observing relationships in Finnish adoptive families: Oulu Family Rating Scale

Adoption studies were intended to separate genetic from environmental “causal” factors. In earlier adoption studies, psychiatric diagnostic labels for the adoptive parents were used as a proxy for the multiple dimensions of the family rearing environment. In the Finnish Adoption Study, research design provided the opportunity to study directly the adoptive family rearing environment. For this purpose 33 sub-scales were selected creating what we call Oulu Family Rating Scale (OPAS, Oulun PerheArviointiSkaala). In this paper, the manual for scoring of these sub-scales is presented.

Die finnische Adoptionsstudie: Kinder schizophrener Mütter, die von anderen Familien adoptiert wurden

Die Aussagekraft herkommlicher genetischer und familiendynamischer Forschungen ist begrenzt, weil die Kinder gestorter Eltern bei eben diesen Eltern aufgewachsen sind. Demgegenuber ist eine Unterscheidung zwischen Erb- und Umweltfaktoren dann moglich, wenn die Kinder im fruhen Alter aus der leiblichen Familie in eine Adoptivfamilie kommen: Adoptierte Kinder bringen von ihren leiblichen Eltern die Erbanlagen mit und wachsen in der familiaren Umgebung der Adoptiveltern auf. Damit ist die Moglichkeit gegeben, Vererbungsund Umweltwirkungen getrennt zu erforschen.

Biologic Mothers in the Finnish Adoptive Family Study; Alternative Definitions of Schizophrenia

Our study was started in 1967, after the International Symposium on Transmission of Schizophrenia organized by David Rosenthal, Ph.D. and Seymour Kety, M.D. (1968). All the participants were highly impressed by the new strategy for separating heredity and environment. Still some problems remained in Rosenthal’s Danish study on adopted-away-offspring of schizophrenics (Rosenthal 1971, Lidz 1981). Their series was rather small. The diagnoses of the index parents were based on hospital records, not on psychiatric interviews. The family environment was not investigated directly, although some historical information was obtained through individual interviews of the offspring, of whom 80% participated. There was also the chance of omitting cases of early onset of schizophrenia in biological parents, because the regulations in Denmark discouraged known schizophrenics from giving their offspring up for adoption. Finally, the diagnostic concepts have changed considerably since the late 50’s, when their study was planned. Because of these problems, we considered it justifiable to replicate the study, including direct family measurements of the rearing environment and personal diagnostic interviews of the biological index parents, too.