Genetic boundaries of the schizophrenia spectrum: evidence from the Finnish Adoptive Family Study of Schizophrenia.
OBJECTIVE
Identification of the genetically related disorders in the putative schizophrenia spectrum is an unresolved problem. Data from the Finnish Adoptive Family Study of Schizophrenia, which was designed to disentangle genetic and environmental factors influencing risk for schizophrenia, were used to examine clinical phenotypes of schizophrenia spectrum disorders in adopted-away offspring of mothers with schizophrenia spectrum disorders.


METHODS
Subjects were 190 adoptees at broadly defined genetic high risk who had biological mothers with schizophrenia spectrum disorders, including a subgroup of 137 adoptees at narrowly defined high risk whose mothers had DSM-III-R schizophrenia. These high-risk groups, followed to a median age of 44 years, were compared diagnostically with 192 low-risk adoptees whose biological mothers had either a non-schizophrenia-spectrum diagnosis or no lifetime psychiatric diagnosis.


RESULTS
In adoptees whose mothers had schizophrenia, the mean lifetime, age-corrected morbid risk for narrowly defined schizophrenia was 5.34% (SE=1.97%), compared to 1.74% (SE=1.00%) for low-risk adoptees, a marginally nonsignificant difference. In adoptees whose mothers had schizophrenia spectrum disorders, the mean age-corrected morbid risk for a schizophrenia spectrum disorder was 22.46% (SE=3.56%), compared with 4.36% (SE=1.51%) for low-risk adoptees, a significant difference. Within the comprehensive array of schizophrenia spectrum disorders, schizotypal personality disorder was found significantly more often in high-risk than in low-risk adoptees. The frequency of the group of nonschizophrenic nonaffective psychoses collectively differentiated high-risk and low-risk adoptees, but the frequencies of the separate disorders within this category did not. The two groups were not differentiated by the prevalence of paranoid personality disorder and of affective disorders with psychotic features.


CONCLUSIONS
In adopted-away offspring of mothers with schizophrenia spectrum disorders, the genetic liability for schizophrenia-related illness (with the rearing contributions of the biological mothers disentangled) is broadly dispersed. Genetically oriented studies of schizophrenia-related disorders and studies of genotype-environment interaction should consider not only narrowly defined, typical schizophrenia but also schizotypal and schizoid personality disorders and nonschizophrenic nonaffective psychoses.
Tienari
Pekka
P
Department of Psychiatry, University of Oulu, PL 5000, 90014 Oulun Yliopisto, Oulu, Finland. ptienari@cc.oulu.fi
Wynne
Lyman C
LC
Läksy
Kristian
K
Moring
Juha
J
Nieminen
Pentti
P
Sorri
Anneli
A
Lahti
Ilpo
I
Wahlberg
Karl-Erik
KE
D000300:Adoption; D000328:Adult; D017668:Age of Onset; D002648:Child; D016241:Child of Impaired Parents; D002675:Child, Preschool; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D007223:Infant; D008297:Male; D010260:Paranoid Personality Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics; D015995:Prevalence; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D012565:Schizophrenic Psychology; D012569:Schizotypal Personality Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics