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Speech disturbances and quality of life in schizophrenia: Differential impacts on functioning and life satisfaction
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ScienceDirect Comprehensive Psychiatry 55 (2014) 693 – 698 www.elsevier.com/locate/comppsych
Speech disturbances and quality of life in schizophrenia: Differential impacts on functioning and life satisfaction Eric J. Tan a,⁎, Neil Thomas a, b , Susan L. Rossell a, b a
Monash Alfred Psychiatry research centre, Monash University Central Clinical School, and The Alfred Hospital, Melbourne, Australia b Brain and Psychological Sciences Research Centre, Swinburne University of Technology, Hawthorn, Australia
Abstract Speech disturbances in schizophrenia impact on the individual’s communicative ability. Although they are considered a core feature of schizophrenia, comparatively little work has been done to examine their impact on the life experiences of patients. This study aimed to examine the relationship between schizophrenia speech disturbances, including those traditionally known as formal thought disorder (TD), and quality of life (QoL). It assessed effects on functioning (objective QoL) and satisfaction (subjective QoL) concurrently, while controlling for the influence of neurocognition and depression. Fifty-four patients with schizophrenia/schizoaffective disorder were administered the MATRICS Consensus Cognitive Battery (MCCB), the PANSS, MADRS (with separate ratings for negative TD [verbal underproductivity] and positive TD [verbal disorganisation and pressured speech]) and Lehman’s QOLI assessing both objective and subjective QoL. Ratings of positive and negative TD, depression, and general neurocognition were entered into hierarchical regressions to explore their relationship with both life functioning and satisfaction. Verbal underproductivity was a significant predictor of objective QoL, while pressured speech had a trend association with subjective QoL. This suggests a differential relationship between speech disturbances and QoL. Verbal underproductivity seems to affect daily functioning and relations with others, while pressured speech is predictive of satisfaction with life. The impact of verbal underproductivity on QoL suggests it to be an important target for rehabilitation in schizophrenia. © 2014 Elsevier Inc. All rights reserved.
1. Introduction As one of the most disabling mental disorders, reducing the negative impact of schizophrenia symptoms on quality of life is a major aim of treatment. Speech disturbances are considered a core schizophrenia symptom [1,2], and describe the aberrant speech patterns and word choices that manifest in conversation. While traditionally and diagnostically known as formal thought disorder (TD), these speech disturbances are no longer seen as deriving solely from disordered thought [3]. We have chosen to retain the term TD here for continuity and ease of reference. The presentation of speech disturbances are broadly categorised under either positive or negative domains. Positive TD symptoms typically exceed normal presentations of speech,
⁎ Corresponding author at: Monash Alfred, Psychiatry Research Centre, Level 4 607 St Kilda Rd, Melbourne, VIC 3004, Australia. Tel.: +61 3 9076 6564; fax: +61 3 9076 6588. E-mail address: [email protected] (E.J. Tan). 0010-440X/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.comppsych.2013.10.016
such as frequent ventures off a topic (derailment) and pressure of speech. Negative TD symptoms represent reductions from the norm, such as monosyllabic or unelaborated responses to questions (poverty of speech). These speech disturbances can result in fragmentation and impaired fluidity [4], and reduce a patient’s ability to successfully communicate intended meanings [5]. TD can thus degrade communication, which is arguably critical to daily functioning. This is a key area of investigation because while only 20% of schizophrenia patients will meet diagnostic criteria for TD, varying levels of speech disturbances will be observed in about 80% of them [6]. Measurement of quality of life (QoL) has proven important in understanding the functional impact of symptoms in schizophrenia. An individual’s QoL can be considered as a statement of his/her daily life experience, with the most common definition relating to the individual’s sense of well-being and satisfaction with his/her life situation [7]. While there is still no agreement on the precise definition of QoL, evidence supports two distinct, though related, components within the concept [8,9] that
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should be assessed concurrently [10]. Objective QoL relates to quantifiable measurements of functioning such as frequency of social contact and financial income, whilst subjective QoL reflects the individual’s reported experience of well-being and life satisfaction. Prevailing evidence suggests that individuals with schizophrenia have a reduced QoL compared with the general population [11–13]. Schizophrenia symptoms established as being related to reduced QoL include increased positive and negative symptomatology [14–16], and depression and anxiety [17–20]. Better neurocognitive ability has also been linked to higher objective but lower subjective QoL [21–23], while better insight seems to reduce subjective QoL [24]. Two previous attempts have been made to relate TD to aspects of QoL. The first study found no association between general TD symptoms and subjective QoL [25]. However, this study neither examined objective QoL nor considered the potential for separate effects of positive and negative TD. Subsequently, another study looked at positive and negative TD separately, finding that verbal underproductivity (negative TD), but not positive TD, predicted social disengagement and reduced friendships [26], a component of objective QoL. They did not however investigate subjective QoL. Taken together, there thus appears to be some evidence that TD relates to QoL, However, the specificity of this association to the relationship between negative TD and objective QoL requires clarifying in a study considering both elements of TD and both subjective and objective QoL. It remains possible that subjective QoL is additionally affected by specific aspects of TD, considering (i) that TD affects communication of meaning [27], and so could conceivably impact on interpersonal relations and functioning, which should then influence satisfaction; and (ii) growing evidence for associations between QoL and schizophrenia symptoms that are comorbid with TD, such as poorer neurocognitive function [28] and reduced insight [29,30]. To this end, this study sought to assess the impact of positive and negative TD on both functioning and satisfaction within the same cohort by measuring both objective and subjective QoL. Following Bowie and Harvey [26], it was hypothesised that negative TD would be associated with lower levels of objective and also subjective QoL. The relationship between positive TD and both objective and subjective QoL will be examined, while accounting for the effects of depression, neurocognition and insight. No specific hypothesis was made for this due to a gap in the literature.
medication (no change in previous 8 weeks). All participants were screened for previous traumatic brain injury, current substance abuse (previous 6 months), previous neurological illness, and proficiency in English. This research received ethical approval from the Alfred Hospital Human Research Ethics Committee, Melbourne. Written voluntary informed consent was collected from all participants prior to assessment. Demographic and clinical characteristics are presented in Table 1. 2.2. Measures 2.2.1. Symptom assessment (incl. insight) The Positive and Negative Syndrome Scale [PANSS; 31] was used to assess schizophrenia symptomatology. Specific items were selected to represent elements of TD; conceptual disorganization (P2) and excitement (P4) for positive TD and lack of spontaneity/flow of conversation (N6) for negative TD. P2 is commonly used as a measure of TD, P4 contains the pressure of speech element characteristic of TD and N6 is akin to poverty of speech (alogia). G12 (Lack of judgment and insight) was used as a basic measure of patient insight. 2.3. Depression The Montgomery–Asberg Depression Rating Scale [MADRS; 32] was selected to provide a brief but comprehensive measure of depression, which has been strongly linked to reduced subjective QoL in chronic schizophrenia [33]. The PANSS depression rating was not used as it is considered to be less sensitive than the MADRS.
Table 1 Demographic and clinical characteristics of the sample (n = 54). Variable
Mean
SD
2.1. Participants
Age (years) Gender (% male) Years of education Premorbid intelligence (WTAR) Employed (%) Partnered (%) Age of onset Length of illness Medication (CPZE) PANSS positive a PANSS negative (minus N6) a PANSS conceptual disorganization (P2) PANSS excitement (P4) PANSS lack of spontaneity/flow of conversation (N6) PANSS Lack of judgment and insight (G12) MCCB Overall Cognitive Score Depression score (MADRS)
43.35 51.9 14.31 101.76 40.7 14.8 23.55 19.77 489.85 12.06 14.04 2.07 1.44 1.70 1.94 35.24 9.76
10.74 – 2.65 13.88 – – 6.67 11.59 439.13 4.82 4.65 1.27 .79 1.02 1.24 12.12 8.64
Fifty-four patients with DSM-IV schizophrenia/schizoaffective disorder were recruited for this study from the Alfred Hospital and surrounding community clinics in Melbourne, Australia. All patients were on stable doses of anti-psychotic
SD: standard deviation; WTAR = Wechsler Test of Adult Reading; CPZE = Chlorpromazine equivalence; PANSS = Positive and Negative Syndrome Scale; MCCB = MATRICS Consensus Cognitive Battery; MADRS = Montgomery–Asberg Depression Rating Scale. aCalculated from PANSS five-factor model [36].
2. Method
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2.4. Neurocognitive assessment and intelligence All participants completed the MATRICS Consensus Cognitive Battery [MCCB; 34] as a comprehensive measure of general cognition. The Overall Cognitive Score from this battery was chosen for the regression analyses. Premorbid intelligence was measured using the Wechsler Test of Adult Reading [WTAR; 35]. 2.5. Quality of Life assessment The Quality of Life Interview [QoLI; 12] has been widely used and provides both objective and subjective measures of life domains, including daily activities, family contact and social functioning. For this study, three measures of objective QoL were selected based on previous research [9,10] and reliance on communicative ability and relation to daily functioning: daily activities and functioning (e.g., going to a movie, shopping, preparing a meal); family relations (e.g., interactions with family members); and social relations (e.g., interactions with close friends). Patientreported satisfaction ratings for these three objective domains were chosen as subjective QoL. 2.6. Statistical Analysis All variables conformed to normal distributions. Scores for each of the objective and subjective QoL measures were converted into z-scores and Pearson’s correlations were run between the variables of interest as a first step. In step 2, a series of hierarchical regressions was used to test the hypothesis that the TD variables contributed independent variance to QoL. This was done separately for both objective and subjective QoL. Only variables which correlated with at least one of the measures of objective or subjective QoL were entered. Two overall mean scores were generated from the QoL variables to independently represent objective QoL and subjective QoL, which were then used in two separate hierarchical regression analyses. In both instances, scores for depression and neurocognition were entered as the first two blocks. N6 was entered into the third block for negative TD, with P2 and P4 in Block 4 for positive TD. This specific ordering of variables allowed for the identification of the unique contribution of TD to QoL beyond depression and general neurocognitive function. The decision was taken to enter negative TD before positive TD based on previous established effects for negative TD on functioning [26], which have not yet been ascertained for positive TD. For positive or negative TD to be established as predicting variance in either or both objective and subjective QoL, separate from both depression and general neurocognitive function, a significant increase in explained variance would have to be observed when blocks 3 and 4 are added. For the TD symptoms, it was also necessary to distinguish the contributed variance from that of broader positive and
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negative symptomatology. This was because the TD measures were taken from the PANSS positive and negative symptomatology subscales, which could possibly confound the results. To do this, associations with the positive symptoms and negative symptoms factors from the five factor PANSS model [36] were examined. We calculated the positive symptoms factor, which does not include items P2 or P4, and a composite version of the negative symptoms factor removing item N6 (items N1, N2, N3, N4, G7 and G16). Correlations between these scores and measures of objective and subjective QoL were calculated. These scores were then entered in place of the positive and negative TD blocks in new hierarchical regressions on mean objective and subjective QoL. All analyses were two-tailed and alpha was set at .05.
3. Results 3.1. Relationships between variables of interest and QoL Pearson’s product moment correlations between TD variables on the PANSS, insight, depression, neurocognition and selected objective and subjective aspects of QoL are presented in Table 2. As seen in Table 2, positive TD variables were associated with higher objective ratings of daily functioning, with a trend towards significance for personal satisfaction. Negative TD was inversely related to objective ratings of daily functioning and participation in social activities. Depression severity was inversely related to both objective and subjective aspects of QoL, while neurocognition was negatively related to satisfaction with daily functioning. Insight did not correlate with either objective or subjective aspects of QoL, and so was excluded from subsequent analyses. Due to the observations that some predictors influenced both aspects of QoL, the decision was taken to include all predictors that correlated with either objective or subjective QoL in both regressions. 3.2. Associations between depression, neurocognition, TD and QoL When depression and neurocognition were entered first into two hierarchical regressions, followed by N6 for negative TD and P2 and P4 for positive TD, differential effects of TD were observed. In the regression with objective QoL, the predictive model was significant only when negative TD was included, F(3,50) = 3.94, p = .013, explaining 15% of the variance in objective QoL scores (see Table 3). Addition of positive TD did not significantly increase the fit of the model. In the regression with subjective QoL, significant changes in R 2 were produced by both depression, F(1,52) = 10.65, p = .002, and neurocognition, F(1,51) = 7.67, p = .001, explaining an incremental 17% and 6% of the variance in subjective QoL scores respectively. Entering negative
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Table 2 Pearson’s correlations for all variables (n = 54). Measures
PANSS P2
PANSS P4
PANSS N6
PANSS G12
MADRS score
CPZE dose
Positive TD PANSS P2 PANSS P4
– .60**
– –
– –
– –
– –
Negative TD PANSS N6
−.01
−.18
–
–
Insight PANSS G12
.60**
.45**
.27*
Depression MADRS score
−.01
−.07
Neurocognition MCCB OCS a
−.38**
−.09
Objective QoL
Subjective QoL
DAF
FAM
SOC
DAF
FAM
SOC
−.02 −.02
.32* .37**
.03 .08
.04 .14
.06 .26^
−.09 .00
.10 .24^
–
−.11
−.32*
−.22
−.30*
.01
.15
.02
–
–
−.22
.09
−.11
−.16
−.03
.01
−.07
.09
−.01
–
.05
.06
−.15
−.34*
−.36**
−.26^
−.34*
−.27^
−.10
−.17
.09
.11
−.05
.02
−.32*
−.02
−.06
DAF = Daily activities and functioning; FAM = frequency of family contact; SOC = frequency of social activities. PANSS = Positive and Negative Syndrome Scale. MADRS = Montgomery–Asberg Depression Rating Scale. CPZE = Medication dose in chlorpromazine equivalence. aOverall Cognitive Score. * = p b .05. ** = p b .01. ^ = at trend level pb.1.
TD did not significantly increase model fit (p = .69), but an additional 8% of variance was explained when entering positive TD variables, F(5,48) = 4.47, p = .002, although this fell just outside statistical significance (p = .062) (see Table 4). 3.3. Relationship of general positive and negative symptoms to QoL When the adapted PANSS negative symptom score was substituted for negative TD in the regression model for objective QoL, a significant R 2 change was observed above neurocognition and depression alone, R 2 change = .13, F(1,50) = 8.06, p = .007. Conversely, R 2 change was not significant when the adapted PANSS positive symptom score was substituted for positive TD in the subjective QoL model, R 2 change = .03, F(1,49) = 1.88, p = .18. 4. Discussion This study presents, to our best knowledge, the first concurrent investigation of objective and subjective QoL in relation to speech disturbances in schizophrenia. In line with Bowie and Harvey [26], negative TD successfully predicted
lower objective QoL, that is, reduced daily activities, family and social contact; however it did not have an effect on subjective QoL. Additionally, a trending relationship was found for positive TD to predict increased subjective QoL, but not objective QoL. This tentative association between TD and self-reported satisfaction is in contrast to the previous null finding [25]. Taken together, these findings support the notion that the speech and communication disturbances induced by TD in schizophrenia do affect QoL, and that this relationship varies depending on type of TD (positive and negative) and QoL component (objective and subjective). Also, largely in line with previous research [28–30], positive and negative TD showed significant correlations with reduced insight and positive TD was correlated with neurocognition, whereas this failed to achieve significance in negative TD. The finding that negative TD predicts reduced objective QoL still strongly emerged after controlling for depression and neurocognitive effects. This suggests that reduction in spontaneous conversation has an independent and significant impact on functioning above mood and cognitive impairments that appears to align with established negative symptom impact on objective QoL [16]. However, negative TD does explain more variance than general negative
Table 3 Multiple regressions for the prediction of objective QoL by depression, neurocognition, negative and positive TD. Predictor
MADRS score MCCB OCS PANSS N6 PANSS P2 PANSS P4 Δ = change.
R2
Standardised beta (β) Block 1
Block 2
Block 3
Block 4
−.20 p=.14 – – – –
−.20 p=.16 .01 p=.96 – – –
−.18 p=.17 −.10 p=.47 −.40 p=.004 – –
−.16 p=.21 −.04 p=.77 −.36 p=.01 .07 p=.70 .15 p=.36
.04 .04 .19 .23
R 2 Change Δ
F
p
.04 .00 .15 .04
2.20 .002 9.29 1.15
.14 .96 .004 .33
E.J. Tan et al. / Comprehensive Psychiatry 55 (2014) 693–698 Table 4 Multiple regressions for the prediction of subjective QoL by depression, neurocognition, negative and positive TD. Predictor
Standardised beta (β) Block 1 Block 2 Block 3 Block 4
M A D R S −..41 −.46 score p=.002 p=.001 MCCB OCS – −.25 p=.049 PANSS N6 – – PANSS P2
–
–
−.46 p=.001 −.24 p=.073 .05 p=.692 –
PANSS P4
–
–
–
−.45 p=.001 −.31 p=.028 .09 p=.459 −.31 p=.063 .37 p=.023
R2
R 2 Change Δ
F
p
.17 .17 10.65 .002 .23 .06 4.07
.049
.23 .00 .16
.69
.32 .08 2.95
.062
Δ = change.
symptoms here, which supports the case for a substantial contribution of negative TD itself towards social isolation in schizophrenia. A possible pathway is that negative TD impairs the ability of schizophrenia patients to communicate with others, resulting in disrupted social relations. This is consistent with longitudinal evidence that verbal underproductivity leads to reduced social engagement [26], which may be compounded by lack of volition. Consequently, the rehabilitation of decreased verbal production in therapy may go some way to remedying these effects. The non-association with subjective QoL possibly indicates that reduced communicability does not directly impact on self-perceived satisfaction. There was a trend toward association between increased positive TD and better subjective QoL, after controlling for depression and neurocognition. The effect of positive TD appeared independent of these, and was a stronger predictor than positive symptoms in general. While it has been suggested that TD is associated with reduced insight, nonsignificant correlations between insight and the two indexes of QoL here do not support a mediating role for insight between TD and QoL. The trending association precludes any definitive interpretations being made about the effect of positive TD on subjective QoL; however, subjective QoL is defined as self-perceived satisfaction, so it is plausible to speculate that the aberrant internal thinking processes associated with positive TD may be involved. Significant correlations between positive TD and neurocognition here raise the possibility of the latter having a role, given longitudinal evidence that it is a long-term predictor of subjective QoL at 3-year follow up [37]. However, given we controlled for neurocognition in this model, further studies would need to investigate this point before more definitive conclusions can be made. The results of the regression analysis do however suggest that the positive association between positive TD and subjective QoL primarily reflects the relationship with P4. Positive TD is heterogeneous [38], and it may be the difficulties in regulating and inhibiting thinking and speech processes, rather than broad verbal
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disorganisation, that are most predictive of subjective QoL. The paradoxical positive correlation with subjective QoL may be due to this element of positive TD being an index of broader difficulties in self-awareness and self-monitoring, which may protect the person from dwelling on the social consequences of their illness [39]. Positive TD generally presents more severely during acute episodes [40], rather than across a long period of time. Negative TD, much like general negative symptoms, tends to be more stable and exacerbated in the long term [41]. Effects on current satisfaction can be state-based, instantaneous and so influenced by the fluid/florid nature of positive TD. However, markers of functioning tend to change more slowly, and are conceivably more likely to be affected by consistent symptom presence, such as that exemplified by negative TD. The minimal and unspontaneous speech that reduces communicability may result in the slow subtle changes to daily routines, and loss of social relationships which are measured in objective QoL. There has been some debate about the primacy of negative symptoms in schizophrenia and factors that may induce secondary negative symptoms (i.e. anti-psychotic drug use) [42]. However, given non-significant correlations between symptoms and medication dose estimates in this sample, it is unlikely that the negative TD observed here is a result of this. These findings come with some caveats. Notably, P4 does not represent a pure measure of speech disorder, with conventional ratings made on the basis of behavioural signs of excitement as well. A review of rating notes indicated that most patients were rated on this item primarily on speech output, supporting our use of this item to provide a more complete characterisation of TD. However this circumstance is specific to this study and must be considered a limitation. Future studies should be more cautious or use a different measure of TD. Severity of TD was in the low range with minimal variability which may reduce the generalizability of results. However, the strong finding with negative TD was consistent with previous research, despite a much smaller sample size. Overall positive and negative symptom scores were also generally lower in this group, in keeping with this sample being made up primarily of community-living stable outpatients. We also only investigated aspects of QoL that are closely linked with communicative ability; TD may indeed only directly impact on the elements of QoL that directly require communication to function properly. Nonetheless, this study provides the first evidence that impaired communication impacts both functioning and satisfaction in schizophrenia, and that positive and negative TDs have differential effects on objective and subjective QoL. We speculate different causal mechanisms for these effects. Further replication is desirable to strengthen the evidence base. These findings support the value and efficacy of the concurrent assessment of objective and subjective QoL. The findings also suggest that in prioritising aspects of symptomatology in terms of their impact upon QoL, addressing verbal underproductivity may represent a
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particularly important consideration in conceptualising rehabilitation needs in schizophrenia. Acknowledgment The authors would like to acknowledge all participants for their time. These results were first presented at the Australasian Schizophrenia Conference 2013 in Melbourne, Australia. References [1] Kraepelin E. Dementia praecox and paraphrenia. Edinburgh: E and S Livingstone; 1919. [2] Bleuler E. Dementia praecox of the group of schizophrenias (J. Zinkin, Trans.). New York: International Universities Press; 1950. [3] Chaika E. Thought disorder or speech disorder in schizophrenia? Schizophr Bull 1982;8(4):587-91. [4] Bergman HF, Preisler G, Werbart A. Communicating with patients with schizophrenia: characteristics of well functioning and poorly functioning communication. Qual Res Psychol 2006;3:121-46. [5] Docherty NM. Cognitive impairments and disordered speech in schizophrenia: thought disorder, disorganization, and communication failure perspectives. J Abnorm Psychol 2005;114(2):269-78. [6] Rodriguez-Ferrera S, McCarthy RA, McKenna PJ. Language in schizophrenia and its relationship to formal thought disorder. Psychol Med 2001;31(2):197-205. [7] Eack SM, Newhill CE. Psychiatric symptoms and quality of life in schizophrenia: a meta-analysis. Schizophr Bull 2007;33(5):1225-37. [8] Ruggeri M, et al. Subjective and objective dimensions of quality of life in psychiatric patients: a factor analytical approach: the South Verona Outcome Project 4. Br J Psychiatry 2001;178:268-75. [9] Lehman AF, Postrado LT, Rachuba LT. Convergent validation of quality of life assessments for persons with severe mental illnesses. Qual Life Res 1993;2:327-33. [10] Narvaez JM, et al. Subjective and objective quality of life in schizophrenia. Schizophr Res 2008;98:201-8. [11] Hermann H, Hawthorne G, Thomas R. Quality of life assessment in people living with psychosis. Soc Psychiatry Psychiatr Epidemiol 2002;37:510-8. [12] Lehman AF. A quality of life interview for the chronically mentally ill. Eval Program Plann 1988;11:51-62. [13] Pitkanen A, et al. Individual quality of life of people with severe mental disorders. J Psychiatr Ment Health Nurs 2009;16(1):3-9. [14] Aksaray G, et al. Neurocognitive deficits and quality of life in outpatients with schizophrenia. Prog Neuropsychopharmacol Biol Psychiatry 2002;26:1217-9. [15] Dan A, et al. A comparative study on quality of life of patients of schizophrenia with and without depression. Psychiatry Res 2011;189(2): 185-9. [16] Savilla K, Kettler L, Galletly C. Relationships between cognitive deficits, symptoms and quality of life in schizophrenia. Aust N Z J Psychiatry 2008;42(6):496-504. [17] Huppert JD, et al. Quality of life in schizophrenia: contributions of anxiety and depression. Schizophr Res 2001;51:171-80. [18] Karow A, et al. PANSS syndromes and quality of life in schizophrenia. Psychopathology 2005;38:320-6. [19] Priebe S, et al. Association between symptoms and quality of life in patients with schizophrenia: a pooled analysis of changes over time. Schizophr Res 2011;133:17-21.
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ScienceDirect Comprehensive Psychiatry 55 (2014) 693 – 698 www.elsevier.com/locate/comppsych
Speech disturbances and quality of life in schizophrenia: Differential impacts on functioning and life satisfaction Eric J. Tan a,⁎, Neil Thomas a, b , Susan L. Rossell a, b a
Monash Alfred Psychiatry research centre, Monash University Central Clinical School, and The Alfred Hospital, Melbourne, Australia b Brain and Psychological Sciences Research Centre, Swinburne University of Technology, Hawthorn, Australia
Abstract Speech disturbances in schizophrenia impact on the individual’s communicative ability. Although they are considered a core feature of schizophrenia, comparatively little work has been done to examine their impact on the life experiences of patients. This study aimed to examine the relationship between schizophrenia speech disturbances, including those traditionally known as formal thought disorder (TD), and quality of life (QoL). It assessed effects on functioning (objective QoL) and satisfaction (subjective QoL) concurrently, while controlling for the influence of neurocognition and depression. Fifty-four patients with schizophrenia/schizoaffective disorder were administered the MATRICS Consensus Cognitive Battery (MCCB), the PANSS, MADRS (with separate ratings for negative TD [verbal underproductivity] and positive TD [verbal disorganisation and pressured speech]) and Lehman’s QOLI assessing both objective and subjective QoL. Ratings of positive and negative TD, depression, and general neurocognition were entered into hierarchical regressions to explore their relationship with both life functioning and satisfaction. Verbal underproductivity was a significant predictor of objective QoL, while pressured speech had a trend association with subjective QoL. This suggests a differential relationship between speech disturbances and QoL. Verbal underproductivity seems to affect daily functioning and relations with others, while pressured speech is predictive of satisfaction with life. The impact of verbal underproductivity on QoL suggests it to be an important target for rehabilitation in schizophrenia. © 2014 Elsevier Inc. All rights reserved.
1. Introduction As one of the most disabling mental disorders, reducing the negative impact of schizophrenia symptoms on quality of life is a major aim of treatment. Speech disturbances are considered a core schizophrenia symptom [1,2], and describe the aberrant speech patterns and word choices that manifest in conversation. While traditionally and diagnostically known as formal thought disorder (TD), these speech disturbances are no longer seen as deriving solely from disordered thought [3]. We have chosen to retain the term TD here for continuity and ease of reference. The presentation of speech disturbances are broadly categorised under either positive or negative domains. Positive TD symptoms typically exceed normal presentations of speech,
⁎ Corresponding author at: Monash Alfred, Psychiatry Research Centre, Level 4 607 St Kilda Rd, Melbourne, VIC 3004, Australia. Tel.: +61 3 9076 6564; fax: +61 3 9076 6588. E-mail address: [email protected] (E.J. Tan). 0010-440X/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.comppsych.2013.10.016
such as frequent ventures off a topic (derailment) and pressure of speech. Negative TD symptoms represent reductions from the norm, such as monosyllabic or unelaborated responses to questions (poverty of speech). These speech disturbances can result in fragmentation and impaired fluidity [4], and reduce a patient’s ability to successfully communicate intended meanings [5]. TD can thus degrade communication, which is arguably critical to daily functioning. This is a key area of investigation because while only 20% of schizophrenia patients will meet diagnostic criteria for TD, varying levels of speech disturbances will be observed in about 80% of them [6]. Measurement of quality of life (QoL) has proven important in understanding the functional impact of symptoms in schizophrenia. An individual’s QoL can be considered as a statement of his/her daily life experience, with the most common definition relating to the individual’s sense of well-being and satisfaction with his/her life situation [7]. While there is still no agreement on the precise definition of QoL, evidence supports two distinct, though related, components within the concept [8,9] that
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should be assessed concurrently [10]. Objective QoL relates to quantifiable measurements of functioning such as frequency of social contact and financial income, whilst subjective QoL reflects the individual’s reported experience of well-being and life satisfaction. Prevailing evidence suggests that individuals with schizophrenia have a reduced QoL compared with the general population [11–13]. Schizophrenia symptoms established as being related to reduced QoL include increased positive and negative symptomatology [14–16], and depression and anxiety [17–20]. Better neurocognitive ability has also been linked to higher objective but lower subjective QoL [21–23], while better insight seems to reduce subjective QoL [24]. Two previous attempts have been made to relate TD to aspects of QoL. The first study found no association between general TD symptoms and subjective QoL [25]. However, this study neither examined objective QoL nor considered the potential for separate effects of positive and negative TD. Subsequently, another study looked at positive and negative TD separately, finding that verbal underproductivity (negative TD), but not positive TD, predicted social disengagement and reduced friendships [26], a component of objective QoL. They did not however investigate subjective QoL. Taken together, there thus appears to be some evidence that TD relates to QoL, However, the specificity of this association to the relationship between negative TD and objective QoL requires clarifying in a study considering both elements of TD and both subjective and objective QoL. It remains possible that subjective QoL is additionally affected by specific aspects of TD, considering (i) that TD affects communication of meaning [27], and so could conceivably impact on interpersonal relations and functioning, which should then influence satisfaction; and (ii) growing evidence for associations between QoL and schizophrenia symptoms that are comorbid with TD, such as poorer neurocognitive function [28] and reduced insight [29,30]. To this end, this study sought to assess the impact of positive and negative TD on both functioning and satisfaction within the same cohort by measuring both objective and subjective QoL. Following Bowie and Harvey [26], it was hypothesised that negative TD would be associated with lower levels of objective and also subjective QoL. The relationship between positive TD and both objective and subjective QoL will be examined, while accounting for the effects of depression, neurocognition and insight. No specific hypothesis was made for this due to a gap in the literature.
medication (no change in previous 8 weeks). All participants were screened for previous traumatic brain injury, current substance abuse (previous 6 months), previous neurological illness, and proficiency in English. This research received ethical approval from the Alfred Hospital Human Research Ethics Committee, Melbourne. Written voluntary informed consent was collected from all participants prior to assessment. Demographic and clinical characteristics are presented in Table 1. 2.2. Measures 2.2.1. Symptom assessment (incl. insight) The Positive and Negative Syndrome Scale [PANSS; 31] was used to assess schizophrenia symptomatology. Specific items were selected to represent elements of TD; conceptual disorganization (P2) and excitement (P4) for positive TD and lack of spontaneity/flow of conversation (N6) for negative TD. P2 is commonly used as a measure of TD, P4 contains the pressure of speech element characteristic of TD and N6 is akin to poverty of speech (alogia). G12 (Lack of judgment and insight) was used as a basic measure of patient insight. 2.3. Depression The Montgomery–Asberg Depression Rating Scale [MADRS; 32] was selected to provide a brief but comprehensive measure of depression, which has been strongly linked to reduced subjective QoL in chronic schizophrenia [33]. The PANSS depression rating was not used as it is considered to be less sensitive than the MADRS.
Table 1 Demographic and clinical characteristics of the sample (n = 54). Variable
Mean
SD
2.1. Participants
Age (years) Gender (% male) Years of education Premorbid intelligence (WTAR) Employed (%) Partnered (%) Age of onset Length of illness Medication (CPZE) PANSS positive a PANSS negative (minus N6) a PANSS conceptual disorganization (P2) PANSS excitement (P4) PANSS lack of spontaneity/flow of conversation (N6) PANSS Lack of judgment and insight (G12) MCCB Overall Cognitive Score Depression score (MADRS)
43.35 51.9 14.31 101.76 40.7 14.8 23.55 19.77 489.85 12.06 14.04 2.07 1.44 1.70 1.94 35.24 9.76
10.74 – 2.65 13.88 – – 6.67 11.59 439.13 4.82 4.65 1.27 .79 1.02 1.24 12.12 8.64
Fifty-four patients with DSM-IV schizophrenia/schizoaffective disorder were recruited for this study from the Alfred Hospital and surrounding community clinics in Melbourne, Australia. All patients were on stable doses of anti-psychotic
SD: standard deviation; WTAR = Wechsler Test of Adult Reading; CPZE = Chlorpromazine equivalence; PANSS = Positive and Negative Syndrome Scale; MCCB = MATRICS Consensus Cognitive Battery; MADRS = Montgomery–Asberg Depression Rating Scale. aCalculated from PANSS five-factor model [36].
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2.4. Neurocognitive assessment and intelligence All participants completed the MATRICS Consensus Cognitive Battery [MCCB; 34] as a comprehensive measure of general cognition. The Overall Cognitive Score from this battery was chosen for the regression analyses. Premorbid intelligence was measured using the Wechsler Test of Adult Reading [WTAR; 35]. 2.5. Quality of Life assessment The Quality of Life Interview [QoLI; 12] has been widely used and provides both objective and subjective measures of life domains, including daily activities, family contact and social functioning. For this study, three measures of objective QoL were selected based on previous research [9,10] and reliance on communicative ability and relation to daily functioning: daily activities and functioning (e.g., going to a movie, shopping, preparing a meal); family relations (e.g., interactions with family members); and social relations (e.g., interactions with close friends). Patientreported satisfaction ratings for these three objective domains were chosen as subjective QoL. 2.6. Statistical Analysis All variables conformed to normal distributions. Scores for each of the objective and subjective QoL measures were converted into z-scores and Pearson’s correlations were run between the variables of interest as a first step. In step 2, a series of hierarchical regressions was used to test the hypothesis that the TD variables contributed independent variance to QoL. This was done separately for both objective and subjective QoL. Only variables which correlated with at least one of the measures of objective or subjective QoL were entered. Two overall mean scores were generated from the QoL variables to independently represent objective QoL and subjective QoL, which were then used in two separate hierarchical regression analyses. In both instances, scores for depression and neurocognition were entered as the first two blocks. N6 was entered into the third block for negative TD, with P2 and P4 in Block 4 for positive TD. This specific ordering of variables allowed for the identification of the unique contribution of TD to QoL beyond depression and general neurocognitive function. The decision was taken to enter negative TD before positive TD based on previous established effects for negative TD on functioning [26], which have not yet been ascertained for positive TD. For positive or negative TD to be established as predicting variance in either or both objective and subjective QoL, separate from both depression and general neurocognitive function, a significant increase in explained variance would have to be observed when blocks 3 and 4 are added. For the TD symptoms, it was also necessary to distinguish the contributed variance from that of broader positive and
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negative symptomatology. This was because the TD measures were taken from the PANSS positive and negative symptomatology subscales, which could possibly confound the results. To do this, associations with the positive symptoms and negative symptoms factors from the five factor PANSS model [36] were examined. We calculated the positive symptoms factor, which does not include items P2 or P4, and a composite version of the negative symptoms factor removing item N6 (items N1, N2, N3, N4, G7 and G16). Correlations between these scores and measures of objective and subjective QoL were calculated. These scores were then entered in place of the positive and negative TD blocks in new hierarchical regressions on mean objective and subjective QoL. All analyses were two-tailed and alpha was set at .05.
3. Results 3.1. Relationships between variables of interest and QoL Pearson’s product moment correlations between TD variables on the PANSS, insight, depression, neurocognition and selected objective and subjective aspects of QoL are presented in Table 2. As seen in Table 2, positive TD variables were associated with higher objective ratings of daily functioning, with a trend towards significance for personal satisfaction. Negative TD was inversely related to objective ratings of daily functioning and participation in social activities. Depression severity was inversely related to both objective and subjective aspects of QoL, while neurocognition was negatively related to satisfaction with daily functioning. Insight did not correlate with either objective or subjective aspects of QoL, and so was excluded from subsequent analyses. Due to the observations that some predictors influenced both aspects of QoL, the decision was taken to include all predictors that correlated with either objective or subjective QoL in both regressions. 3.2. Associations between depression, neurocognition, TD and QoL When depression and neurocognition were entered first into two hierarchical regressions, followed by N6 for negative TD and P2 and P4 for positive TD, differential effects of TD were observed. In the regression with objective QoL, the predictive model was significant only when negative TD was included, F(3,50) = 3.94, p = .013, explaining 15% of the variance in objective QoL scores (see Table 3). Addition of positive TD did not significantly increase the fit of the model. In the regression with subjective QoL, significant changes in R 2 were produced by both depression, F(1,52) = 10.65, p = .002, and neurocognition, F(1,51) = 7.67, p = .001, explaining an incremental 17% and 6% of the variance in subjective QoL scores respectively. Entering negative
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Table 2 Pearson’s correlations for all variables (n = 54). Measures
PANSS P2
PANSS P4
PANSS N6
PANSS G12
MADRS score
CPZE dose
Positive TD PANSS P2 PANSS P4
– .60**
– –
– –
– –
– –
Negative TD PANSS N6
−.01
−.18
–
–
Insight PANSS G12
.60**
.45**
.27*
Depression MADRS score
−.01
−.07
Neurocognition MCCB OCS a
−.38**
−.09
Objective QoL
Subjective QoL
DAF
FAM
SOC
DAF
FAM
SOC
−.02 −.02
.32* .37**
.03 .08
.04 .14
.06 .26^
−.09 .00
.10 .24^
–
−.11
−.32*
−.22
−.30*
.01
.15
.02
–
–
−.22
.09
−.11
−.16
−.03
.01
−.07
.09
−.01
–
.05
.06
−.15
−.34*
−.36**
−.26^
−.34*
−.27^
−.10
−.17
.09
.11
−.05
.02
−.32*
−.02
−.06
DAF = Daily activities and functioning; FAM = frequency of family contact; SOC = frequency of social activities. PANSS = Positive and Negative Syndrome Scale. MADRS = Montgomery–Asberg Depression Rating Scale. CPZE = Medication dose in chlorpromazine equivalence. aOverall Cognitive Score. * = p b .05. ** = p b .01. ^ = at trend level pb.1.
TD did not significantly increase model fit (p = .69), but an additional 8% of variance was explained when entering positive TD variables, F(5,48) = 4.47, p = .002, although this fell just outside statistical significance (p = .062) (see Table 4). 3.3. Relationship of general positive and negative symptoms to QoL When the adapted PANSS negative symptom score was substituted for negative TD in the regression model for objective QoL, a significant R 2 change was observed above neurocognition and depression alone, R 2 change = .13, F(1,50) = 8.06, p = .007. Conversely, R 2 change was not significant when the adapted PANSS positive symptom score was substituted for positive TD in the subjective QoL model, R 2 change = .03, F(1,49) = 1.88, p = .18. 4. Discussion This study presents, to our best knowledge, the first concurrent investigation of objective and subjective QoL in relation to speech disturbances in schizophrenia. In line with Bowie and Harvey [26], negative TD successfully predicted
lower objective QoL, that is, reduced daily activities, family and social contact; however it did not have an effect on subjective QoL. Additionally, a trending relationship was found for positive TD to predict increased subjective QoL, but not objective QoL. This tentative association between TD and self-reported satisfaction is in contrast to the previous null finding [25]. Taken together, these findings support the notion that the speech and communication disturbances induced by TD in schizophrenia do affect QoL, and that this relationship varies depending on type of TD (positive and negative) and QoL component (objective and subjective). Also, largely in line with previous research [28–30], positive and negative TD showed significant correlations with reduced insight and positive TD was correlated with neurocognition, whereas this failed to achieve significance in negative TD. The finding that negative TD predicts reduced objective QoL still strongly emerged after controlling for depression and neurocognitive effects. This suggests that reduction in spontaneous conversation has an independent and significant impact on functioning above mood and cognitive impairments that appears to align with established negative symptom impact on objective QoL [16]. However, negative TD does explain more variance than general negative
Table 3 Multiple regressions for the prediction of objective QoL by depression, neurocognition, negative and positive TD. Predictor
MADRS score MCCB OCS PANSS N6 PANSS P2 PANSS P4 Δ = change.
R2
Standardised beta (β) Block 1
Block 2
Block 3
Block 4
−.20 p=.14 – – – –
−.20 p=.16 .01 p=.96 – – –
−.18 p=.17 −.10 p=.47 −.40 p=.004 – –
−.16 p=.21 −.04 p=.77 −.36 p=.01 .07 p=.70 .15 p=.36
.04 .04 .19 .23
R 2 Change Δ
F
p
.04 .00 .15 .04
2.20 .002 9.29 1.15
.14 .96 .004 .33
E.J. Tan et al. / Comprehensive Psychiatry 55 (2014) 693–698 Table 4 Multiple regressions for the prediction of subjective QoL by depression, neurocognition, negative and positive TD. Predictor
Standardised beta (β) Block 1 Block 2 Block 3 Block 4
M A D R S −..41 −.46 score p=.002 p=.001 MCCB OCS – −.25 p=.049 PANSS N6 – – PANSS P2
–
–
−.46 p=.001 −.24 p=.073 .05 p=.692 –
PANSS P4
–
–
–
−.45 p=.001 −.31 p=.028 .09 p=.459 −.31 p=.063 .37 p=.023
R2
R 2 Change Δ
F
p
.17 .17 10.65 .002 .23 .06 4.07
.049
.23 .00 .16
.69
.32 .08 2.95
.062
Δ = change.
symptoms here, which supports the case for a substantial contribution of negative TD itself towards social isolation in schizophrenia. A possible pathway is that negative TD impairs the ability of schizophrenia patients to communicate with others, resulting in disrupted social relations. This is consistent with longitudinal evidence that verbal underproductivity leads to reduced social engagement [26], which may be compounded by lack of volition. Consequently, the rehabilitation of decreased verbal production in therapy may go some way to remedying these effects. The non-association with subjective QoL possibly indicates that reduced communicability does not directly impact on self-perceived satisfaction. There was a trend toward association between increased positive TD and better subjective QoL, after controlling for depression and neurocognition. The effect of positive TD appeared independent of these, and was a stronger predictor than positive symptoms in general. While it has been suggested that TD is associated with reduced insight, nonsignificant correlations between insight and the two indexes of QoL here do not support a mediating role for insight between TD and QoL. The trending association precludes any definitive interpretations being made about the effect of positive TD on subjective QoL; however, subjective QoL is defined as self-perceived satisfaction, so it is plausible to speculate that the aberrant internal thinking processes associated with positive TD may be involved. Significant correlations between positive TD and neurocognition here raise the possibility of the latter having a role, given longitudinal evidence that it is a long-term predictor of subjective QoL at 3-year follow up [37]. However, given we controlled for neurocognition in this model, further studies would need to investigate this point before more definitive conclusions can be made. The results of the regression analysis do however suggest that the positive association between positive TD and subjective QoL primarily reflects the relationship with P4. Positive TD is heterogeneous [38], and it may be the difficulties in regulating and inhibiting thinking and speech processes, rather than broad verbal
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disorganisation, that are most predictive of subjective QoL. The paradoxical positive correlation with subjective QoL may be due to this element of positive TD being an index of broader difficulties in self-awareness and self-monitoring, which may protect the person from dwelling on the social consequences of their illness [39]. Positive TD generally presents more severely during acute episodes [40], rather than across a long period of time. Negative TD, much like general negative symptoms, tends to be more stable and exacerbated in the long term [41]. Effects on current satisfaction can be state-based, instantaneous and so influenced by the fluid/florid nature of positive TD. However, markers of functioning tend to change more slowly, and are conceivably more likely to be affected by consistent symptom presence, such as that exemplified by negative TD. The minimal and unspontaneous speech that reduces communicability may result in the slow subtle changes to daily routines, and loss of social relationships which are measured in objective QoL. There has been some debate about the primacy of negative symptoms in schizophrenia and factors that may induce secondary negative symptoms (i.e. anti-psychotic drug use) [42]. However, given non-significant correlations between symptoms and medication dose estimates in this sample, it is unlikely that the negative TD observed here is a result of this. These findings come with some caveats. Notably, P4 does not represent a pure measure of speech disorder, with conventional ratings made on the basis of behavioural signs of excitement as well. A review of rating notes indicated that most patients were rated on this item primarily on speech output, supporting our use of this item to provide a more complete characterisation of TD. However this circumstance is specific to this study and must be considered a limitation. Future studies should be more cautious or use a different measure of TD. Severity of TD was in the low range with minimal variability which may reduce the generalizability of results. However, the strong finding with negative TD was consistent with previous research, despite a much smaller sample size. Overall positive and negative symptom scores were also generally lower in this group, in keeping with this sample being made up primarily of community-living stable outpatients. We also only investigated aspects of QoL that are closely linked with communicative ability; TD may indeed only directly impact on the elements of QoL that directly require communication to function properly. Nonetheless, this study provides the first evidence that impaired communication impacts both functioning and satisfaction in schizophrenia, and that positive and negative TDs have differential effects on objective and subjective QoL. We speculate different causal mechanisms for these effects. Further replication is desirable to strengthen the evidence base. These findings support the value and efficacy of the concurrent assessment of objective and subjective QoL. The findings also suggest that in prioritising aspects of symptomatology in terms of their impact upon QoL, addressing verbal underproductivity may represent a
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