Thought disorders are commonly associated with psychiatric disorders and especially considered a primary feature of schizophrenia. The thinking and speech of schizophrenic patients are confused and disorganized and contain many idiosyncratic and peculiar phrases [15,16,26]. Among schizophrenia patients, thought disorder most often occurs during the acute phase of the disease [3,12,19]. However, some patients continue to have thought disorder even after the acute phase, while improvements in specific aspects of thought disorder have also been reported. Thought disorder is present in other psychiatric disorders as well. Previous studies have revealed thought disorders in patients with affective [6,23,36], schizoid [37,38], and borderline personality disorder [9,11], in autistic Reference Dykens, Volkmar and Glick and bulimic children Reference Smith, Hillard and Roll, and in children with attention-deficit hyperactivity disorder (ADHD) Reference Caplan, Guthrie, Tang, Nuechterlein and Asarnow.
Although thought disorders have been reported to be present in several psychiatric disorders, only a few studies have explored whether thought disorders have trait-like (stable) features. Marengo and Harrow Reference Marengo, Harrow, Tsuang and Simpson evaluated thought disorder in schizophrenia, schizoaffective disorder, and other psychotic and non-psychotic disorders at 2, 4.5, and 7.5 years after index hospitalization, and they found the stability of thought disorder to be most prominent in schizophrenia (correlations of 0.42–0.47, depending on the length of follow-up). Thought disorder was also stable in the other diagnostic categories, although this stability was quite low and did not last throughout the whole follow-up period. Earle-Boyer et al. Reference Earle-Boyer, Levinson, Grant and Harvey found negative thought disorder 10 days after acute admission to be relatively consistent across admissions in schizophrenics, but less consistent in manic patients. Adair and Wagner Reference Adair and Wagner studied the Rorschach protocols of 50 outpatients with schizophrenia who had been tested twice at an average interval of 6.4 years. They found no significant differences in the group mean of unusual verbalizations (UVs) scores between the first and second tests. The correlations between the tests were, however, modest at best (r = 0.16–0.50).
Thought disorders are commonly related to psychiatric disorders. However, it is noticeable that the occurrence of minor cognitive slippages are possible in healthy individuals as well. They occur most frequently during periods of anxiety or fatigue Reference Solovay, Shenton and Holzman. The early presence of some categories of thought disorder in healthy individuals has also been found to predict future psychiatric disorders Reference Metsänen, Wahlberg, Saarento, Tarvainen, Miettunen and Koistinen.
Generally speaking, thought disorder appears to be a trait, at least in some subgroups of schizophrenic and manic patients [4,13]. However, previous studies have also shown that thought disorder could have both trait and state (depending on context) features in psychiatric patients [14,22]. Among healthy individuals, the occurrence of thought disorders could be assumed to be more a state-like feature. On the other hand, Wahlberg et al. Reference Wahlberg, Lyman, Keskitalo, Nieminen, Moring and Läksy reported communication deviance to be a trait-like characteristic among adult subjects (r = 0.58). Subscales measuring “thinking problems” (close to the thought disorder index, TDI scale by Johnston and Holzman Reference Johnston and Holzman) had some stability among adult subjects (language anomalies: r = 0.35; reasoning problems: r = 0.29), but not among subjects aged 20 years or younger.
1.1. Aims of the study
In this study, we investigated whether thought disorders were permanently present among the adoptees in the Finnish adoptive study of schizophrenia. Two assessments of the TDI sum scores on the Rorschach (TDR) of the adoptees Reference Johnston and Holzman, the TDR at the initial assessment and the TDR at follow-up, were performed. In addition, comparisons of the TDR mean scores between genders, between adoptees at low and high genetic risk, and according to psychiatric status were conducted both at baseline and at follow-up.
2. Material and methods
The subjects for this assessment were drawn from the Finnish adoptive family study of schizophrenia [30–Reference Tienari, Wynne, Moring, Läksy, Nieminen and Sorri32]. The total Finnish national sample of high-risk (HR) adoptions includes the adoptive families of all the children adopted away by women hospitalized because of schizophrenia (or paranoid psychosis) in Finland during 1960–1979 Reference Tienari, Sorri and Lahti. Women were excluded if they had an organic brain syndrome, severe mental retardation, primary alcoholism (preceding schizophrenia), or any other major physical illness. Adoptees were excluded if they had been adopted by a relative, adopted abroad, or adopted after the age of 4 years. The final sample included 190 genetically HR offspring whose biological mothers had verified DSM-III-R diagnoses of the broad schizophrenia spectrum [17,32,33]. The HR offspring were blindly compared with 192 adoptees at low genetic risk (LR), who had been adopted away from biological mothers with non-spectrum diagnoses or no psychiatric disorder (NPD).
All adoptees were evaluated twice. At the initial assessment, the psychiatric status of the adoptees was assessed. Individual Rorschach was part of the study to evaluate the thought disorders and communication patterns of the adoptees and their family members. The adoptees were independently re-examined in the same manner after a mean interval of 11 years. The mean follow-up period was 11 years for the HR adoptees and 12 years for the LR adoptees. The difference was not statistically significant. The design, sampling, and diagnostic procedures of the adoption study as a whole have been described earlier [30–Reference Tienari, Wynne, Moring, Läksy, Nieminen and Sorri32].
The subsample discussed in this report included the 158 adoptees whose thought disorder had been assessed by TDI both at the baseline of the study and at follow-up. A further inclusion criterion was that the Rorschach records had been tape-recorded and transcribed. Of these subjects, 78 were HR and 80 LR adoptees. The demographic and clinical data of the subjects according to their genetic status are presented in Table 1.
a Student’s t-test was used to assess the group differences.
b The differences in the groups was assessed by using χ 2-test.
c Social group classification is based on the main provider’s occupation and education. The basis to this classification was the social respect to different occupation. The first group included occupations which were in managerial positions, the second one enterpreneurs, foremen, upper functionaries, the third one skilled workers and lower functionaries and the fourth class unskilled workmen.
The TDI scale was developed by Johnston and Holzman Reference Johnston and Holzman. TDI tags, classifies, and measures putative disturbances in thinking, and it allows assessment of both qualitative and quantitative disturbances of thought. To assess thought disorder by TDI, any verbal sample can be used, but the technique is most commonly applied to responses to Rorschach cards. Clinical experience has shown that by using TDI, it is possible to find a range of severity of thought disorders from mild to severe Reference Holzman, Shenton and Solovay. Therefore, a revised version of TDI includes 24 categories weighted along a continuum of severity (0.25, 0.50, 0.75 and 1.0) Reference Solovay, Shenton and Holzman.
In the present study, the sum of weighted TDI scores on Rorschach (TDR) divided by the number of Rorschach responses was used to assess the stability of thought disorders (the full 10-card procedure) at the initial assessment and at follow-up. The Rorschach test is a rich source of deviant verbalization, and the subjects cannot use any overlearned or stereotyped answers. In addition, in the Rorschach procedure it is not possible to draw any conclusions concerning the correctness of the answers, and this stimulate the person’s potential liability to produce thought disorder under environmental stress. The use of the Rorschach procedure also permits the administration and scoring without knowledge of the purpose of the study. However, the Rorschach test is a rather time-consuming method, and the test situation could thus be quite fatiguing to the subjects. The examiners must also have extremely good education in the use of the method to guarantee reliable results. In this study, the tests were audiotaped and transcribed. The developers of the TDI scale [15,16] used weighted scores, and the following formula was applied to calculate the TDI on the Rorschach score (TDR),
The scoring of the Rorschachs for TDR was carried out from transcribed protocols at the initial assessment by four psychologists unaware of the subjects’ relatedness to their biological and adoptive families or their psychiatric diagnoses. They only knew the subjects’ age, sex, and occupation. The intraclass correlation coefficient (ICC) between the pairs of psychologists was 0.94 for TDR, 0.92 for 0.25 level, 0.92 for 0.50 level, 0.86 for 0.75 level, and 0.66 for 1.0 level, The scoring at follow-up was made by one psychologist (M. Metsänen), again unaware of the subjects’ relatedness to their biological and adoptive families and their psychiatric diagnoses. As at the initial assessment, she only knew the subjects’ age, sex, and occupation. Reliability was checked (n = 31) by the single-measure ICC between the two psychologists (M. Metsänen and K.-E. Wahlberg). The ICC’s were 0.98 for TDR, 0.85 for 0.25 level, 0.92 for 0.50 level, and 0.95 for 0.75 level.
2.3. Adoptees’ DSM-III-R diagnoses
To evaluate the stability of TDI between different psychiatric disorders, the adoptees’ mental disorders were determined by psychiatrists blind to their HR/LR status. The diagnoses were made according to the DSM-III-R criteria [2,31] at maximum certainty, i.e. for a disorder to be diagnosed as probable or definite. The kappa coefficient for inter-rater reliability between the different raters was found to be good (kappa 0.71–0.80) Reference Tienari, Wynne, Moring, Läksy, Nieminen and Sorri. Earlier findings have indicated that the offspring of a schizophrenic parent have an elevated risk for schizophrenia and schizophrenia spectrum disorders [10,21,32], but also for psychiatric disorders of all kinds [21,24,32]. Therefore, the study sample was divided into two groups. The first group consisted of adoptees without any psychiatric disorder (NPD). The second group included adoptees with any psychiatric disorder (APD).
2.4. Statistical methods
The group differences in the categorical variables were assessed with the χ 2-test and those in the continuous variables with Student’s t-test. The mean difference in TDR scores was examined by using analysis of covariance (ANCOVA) Reference Tabachnick and Fidell. In the first ANCOVA, the mean difference in TDR at baseline between the groups (gender, genetic risk, and psychiatric disorder at baseline) was determined after controlling for age at baseline. In the second ANCOVA, the mean difference in TDR at follow-up between the groups (gender, genetic risk, and psychiatric disorder at follow-up) was assessed after controlling for age at follow-up and TDR at baseline. The Tukey–Kramer method was used as an adjustment procedure for multiple testing in both ANCOVA tests. F-statistics and associated P-values from ANCOVA are reported for each main effect (gender, genetic risk, and psychiatric disorder) and their interactions are reported for the covariates. Statistical analyses were performed with the SPSS version SPSS (SPSS Inc.) and the SAS version 8.2 (SAS Institute, Cary, NC).
As seen in Table 2, the variation in the baseline TDR scores was statistically significantly associated with gender, but not with the other main effects (genetic risk, psychiatric status) or their interactions. Female adoptees had significantly higher mean scores in TDR at baseline compared to men.
a ANCOVA was used to assess the statistical significance of the mean difference in baseline scores among groups (genetic risk, gender, psychiatric status) after adjustment for age of the adoptees at the baseline and correction for multiple comparisons with Tukey–Kramer method.
Table 3 shows that TDR measured at the initial assessment, statistically significantly predicted the variation in TDR at follow-up. However, no difference in the mean scores of TDR was found between the genders, between the LR and HR adoptees, or according to psychiatric status, and none of the interactions reached statistical significance.
a ANCOVA was used to assess the statistical significance of the mean difference in follow-up scores among groups (genetic risk, gender, psychiatric status) after adjustment for TDR at initial assessment and age of the adoptees at follow-up and correction for multiple comparisons with Tukey–Kramer method.
We were here able to demonstrate the stability of thought disorders among adoptees from the Finnish adoptive family study of schizophrenia. However, no difference in the mean scores of thought disorders could be found according to the genetic or psychiatric status of the adoptees in either the initial or the follow-up assessment of thought disorders.
Only a few studies have been made to investigate the stability of thought disorder. Previous reports have included rather short (6–7 years) follow-ups, and the stability of thought disorder has been examined with the help of correlation coefficients. In this study, it was possible to explore whether thought disorder had remained unchanged during 11 years of follow-up after controlling for age, gender, genetic risk, and mental disorder and to assess this stability by using an appropriate statistical method. Furthermore, to our knowledge, this is the first report where TDI was used as a method to assess the stability of thought disorder in a longitudinal study setting.
In the present study, the TDR at the initial assessment was found to predict statistically significantly the TDR of the adoptees measured at follow-up. Furthermore, the number of thought disorders decreased during the follow-up period, probably because of the maturation of thought functions. Despite the decrease of thought disorders, the TDR scores turned out to be a state-like feature at follow-up. However, the genetic risk did not affect the stability of thought disorder. One explanation could be that TDR scores may also be connected with environmental factors, and that the genetic variables do not in themselves influence on the stability of thought processes. In an earlier study, Wahlberg et al. Reference Wahlberg, Wynne, Oja, Keskitalo, Pykäläinen and Lahti indicated that one thought disorder factor, namely ‘idiosyncratic verbalization’, was linked not only with the genetic risk but also with the communication patterns of the adoptive rearing parents. In our study, only genetic factors were taken into account, while environmental variables were not.
Psychiatric status was not associated with the stability of thought disorder. Previous studies have reported thought disorders to be stable in subjects with psychiatric disorders, especially schizophrenia. One explanation for our result could be the distribution of the adoptees’ diagnoses in our sample. Our study included only three schizophrenic subjects, and other severe mental disorders were rare too.
The stability of thought disorder was not related to gender. However, we obtained quite an interesting gender-related result at the initial assessment. Women had significantly more thought disorders than men. Yurgelun-Todd et al. Reference Yurgelun-Todd, Killgore and Young reported sex-specific developmental differences in the relations between cerebral structure and function, and it is thus possible that at the initial test situation, the anxiety experienced by the women was so high that it affected their thought processes. Previous studies have shown that some psychiatric disorders, such as eating disorders, anxiety disorders, and depression, including major depression, dysphoria, seasonal affective disorder, posttraumatic stress disorder, panic disorder, and generalized anxiety disorder are more common among women Reference Strober, Freeman, Lampter, Diamond and Kaye. It is thus possible that in a stressful situation, the thought functions of women are more vulnerable to confusion, and thought disorders appear.
We report new information about the stability of thought disorder from a longitudinal perspective. Our results raise the question of whether it is possible to influence thought disorders by any interventions. It would also be interesting to know whether the achieved changes could be stable. Above all, a further challenge in the future is to explore the possible environmental factors that influence the stability of thought disorders.
This research was supported in part by grant MH39663 from the Public Health Service, by a grant from the Scottish Rite Schizophrenia Research Program, N.M.J., USA, by The Academy of Finland, The Jalmari and Rauha Ahokas Foundation, Yrjö Jansson Foundation, The Alma and K.A. Snellman Foundation, Oulu, Finland; Päijät-Häme Central Hospital, and Department of Psychiatry, Oulu University Hospital. We thank Heljä Anias, MA, Ilpo Lahti, MD, Juha Moring, MD, Mikko Naarala, MD, and Anneli Sorri, MD. for contributing to the psychological testing and psychiatric diagnosing of subjects in this study.