Abstract The study aimed to assess the Stability of Communication Deviance of 166 adoptive families recruited into the Finnish adoptive family study, including 76 high-risk children and 90 controls. The biological mothers of the high- risk children had been schizophrenic at some stage. The Communication Deviance shown by the adoptive parents and the adopted children was evaluated on the individual and family Rorschach Communication Deviance (CD) scales and, in the case of the parents, also the couple Rorschach tests. The thought disorders of the adopted children were evaluated on the Thought Disorder scale. The following statistical tests were used: χ2 -compatibility test, Spearman correlation test and Mann - Whitney U -test, logistic regression analysis and Mantel - Haenzel stratified χ2 test to compare the cross-tabulations. Communication Deviance was notably permanent in a variety of interactive situations. The parents showed most permanence between individual and couple Rorschach tasks and spouse and the family tasks. The presence of the children altered parental communication and the presence of the parents altered the children's communication: the impact was circular, and its magnitude depended on the clarity of communication by both parties. A high risk adoptee did not affect of Communication Deviance shown by the adoptive parents, except in family situations. The adoptive parents of high-risk children were more sensitive to the child's presence and showed abundant family CD more often than the control parents. Most of the adoptive parents of high-risk children produced a lot of CD in all situations studied, which implies that Communication Deviance is a circular phenomenon, whereby the child further enhances the basically incoherent communication between the parents.The control children's thought disorders were related to the compatibility of the adoptive parents' Communication Deviance, and to the degree of parental CD in couple and family tasks while those of the high-risk children were not. Part of the adopted children's thought disorders were more closely related to genetic vulnerability, being predicted by parental Communication Deviance in individual situations, but not in couple or family situations. Communication Deviance is so permanent as to be largely resistant to therapy. Constantly ambiguous parental communication is an environmental factor in a child's life and interferes with the development of his or her thinking. By behavioral therapy we can learn to make family communication less ambiguous.