Psychiatric syndromes comorbid with mental retardation: Differences in cognitive and adaptive skills

JOURNAL OF PSYCHIATRIC RESEARCH

Journal of Psychiatric Research 41 (2007) 795–800

www.elsevier.com/locate/jpsychires

Psychiatric syndromes comorbid with mental retardation: Differences in cognitive and adaptive skills Santo F. Di Nuovo b

a,*

, Serafino Buono

b

a University of Catania, Faculty of Education, 2, Ofelia, 95124 Catania, Italy Scientific Research Institute for Diagnosis and Therapy IRCCS Oasi, 73, Conte Ruggero 94018 Troina, Italy

Received 6 September 2005; received in revised form 23 February 2006; accepted 24 February 2006

Abstract The study concerns the specific cognitive and adaptive skills of persons dually diagnosed with mental retardation (MR) and comorbid pathologies, as schizophrenia, personality and mood disorders, pervasive developmental disorders, epilepsy and ADHD. The sample was composed of 182 subjects, diagnosed as mild or moderate MR level, age range from 6 years 8 months to 50 years 2 months, mean age 17.1 (standard deviation 7.9). All the subjects were inpatients in a specialized structure for the diagnosis and the treatment of MR. The instruments of the study were Wechsler Intelligence Scale (WAIS-R or WISC-R according to the chronological age of subjects) and Vineland Adaptive Behavior Scale (VABS). Results confirm that comorbidity is a factor differentiating among mentally retarded subjects. Both verbal processes requiring memory retrieval and visuo-spatial processes are involved as differentiating features. ADHD strongly increases the impairment of cognitive skills, while behavioral disorders are less damaging in MR performance. In adult samples, the differentiating role of comorbid syndromes in MR individuals is reduced for cognitive skills, and limited to some basic verbal abilities, more impaired in mood disorder, less in schizophrenic disorder. The areas of adaptation and socialization, motor and daily living skills, are impaired more in generalized development disturbances than in comorbid schizophrenic and personality and mood disorders. An accurate psychological assessment of dual diagnoses is useful in detecting the specific underlying processes differentiating the comorbid syndromes, and in planning an appropriate rehabilitative treatment. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Cognition; Adjustment; Pathological syndromes; Mental retardation; Comorbidity

1. Introduction Comorbidity in mental retardation (MR) is an intriguing puzzle for researchers and professionals. From a theoretical point of view, it is of great relevance to know what comorbidity ‘adds’ to basic cognitive impairment, or what interaction happens between impaired cognitive development and behavioral disorders of attention, mood, personality, and thought processes. In the perspective of the practitioner, early and accurate differential diagnosis and intervention may *

Corresponding author. Tel.: +39 095 7466301; fax: +39 095 316792. E-mail address: [email protected] (S.F. Di Nuovo). 0022-3956/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpsychires.2006.02.011

have a profound impact on the quality of rehabilitative processes. The comorbidity between MR and psychological pathology has been widely debated in the literature (Jacobson, 1990; Fletcher and Dosen, 1993; Matson and Barrett, 1993; Berrios, 1994; Rojahn and Tasse, 1996; Tonge and Bouras, 1999). Comorbidity is high in intellectually disabled adults (Moss and Glidden, 2001), children and adolescents (Gillberg et al., 1986; Dekker and Koot, 2003, for a review, Wallander et al., 2003). Overall, the international classification systems (e.g., ICD-10) and other studies (Masi, 1998; Szymanski and King, 1999; Rush et al., 2004) report that the prevalence of psychopathology in subjects with MR is nearly 4 times

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higher than that found in the general population. Confirming these epidemiological data, a recent review on the mental health status of people with MR (Kerker et al., 2004) pointed out that available evidence reveals inconsistent estimates of the prevalence of behavioral specific syndromes. Quite surprisingly, Cowley et al. (2004) found that a lower incidence of any psychopathology was associated with more severe MR, presence of epilepsy, and residence with the family. As regards epilepsy, despite prevalence rates of this pathology are 30 times higher in MR than in the general population, there are few studies on its relationship with cognitive and adaptive impairments typical of mentally disabled people (Espie et al., 2003). Little is known also about concomitant behavioral and emotional problems in children with MR and attention deficit disorder with hyperactivity (ADHD) (Pearson et al., 2000). Indeed, there is evidence that ADHD is more common in this population than among the non MR population, and that rates of hyperactivity increase with severity of disability (Masi, 1998; Seager and O’Brien, 2003). Handen et al. (1994) demonstrated significant differences in classroom behavior between groups of MR children with and without ADHD. More studies focused on the co-occurrence between MR and psychopathological disturbances, i.e., attention to mood, personality, and thought disorders. Although MR may be viewed as confounding the diagnosis and treatment of psychiatric illness, the knowledge about the development of this co-occurrence of pathologies is a challenge to modify the developmental outcomes of children with MR (Sachs et al., 2000). The impact of MR on personality development is confirmed by the high psychopathological vulnerability of the mentally disabled (Masi, 1998). Some attempts have been made to establish objective diagnostic criteria for psychiatric disorders in persons with MR. Mood or schizophrenic disorders, and a wide range of emotional and behavior disorders often coexist with MR at different ages (Barrett et al., 1992; Fuller and Sabatino, 1998; Masi et al., 1999). The presence of the full range of affective disorders has been demonstrated in persons with MR (Sovner and Hurley, 1983), but, if affective disorders do occur in all forms in persons with MR, in turn the presence and degree of intellectual disability modify manifestations of these disorders (Girimaji, 2000). More generally, there is an established relationship between social skills and maladaptive behaviors (Rojahn et al., 2004); according to Bielecki and Swender (2004) social skills deficits and excesses are a defining aspect of MR. Examining recent research evidence and reviews about personality disorder in intellectual disability, Torr (2003) underlines that research has been limited by methodological shortcomings, as reduced reliability and validity of the tools used for the assessment. This

reflects the lack of conceptual clarity about the fundamental constructs of personality disorder in intellectual disability. There is good evidence that the prevalence rates of psychiatric and behavioral disorders are increased in this population but the factors that contribute to increased risk or are protective have not been established (Holland, 1999). So, the causal direction of the relationship between these variables is still unclear: mental retardation involves strengths and limitations in cognitive adaptive functioning that may coexist with or lead to impairment in emotional and social role functioning. In mental health crisis, on the other hand, the inappropriate use of cognitive abilities is a primary component of psychiatric disorders. Researchers have traditionally emphasized prevalence issues, but an etiological approach should be promoted (Dykens, 2000; Dykens and Hodapp, 2001). From an applied point of view, standard practice in the clinical care of individuals with MR has often undervalued impairments in mental health and behavioral functioning (Fuller and Sabatino, 1998). Although several methods have been devised to obtain empirical classifications of behavioral problems in MR subjects (e.g., Brown et al., 2004) there is still a tendency to under diagnose psychiatric disorders in the developmentally retarded population (Rush et al., 2004). A number of studies demonstrate that the social competence of individuals with MR and comorbid psychopathology can be enhanced with social skills training. However, to design an effective training, an accurate assessment of adaptive and social functioning must first be conducted (Bielecki and Swender, 2004). The assessment of psychiatric disorders in MR persons is important to validate the dual diagnosis, and to plan appropriate mental health services (Reiss, 1994). When signs of a comorbid mental disorder are identified in MR, further diagnostic assessment will permit differential diagnosis and a specific etiological treatment (Weisblatt, 1994). Beyond the well-established conclusion that comorbidity, in general, reduces performance and adjustment, if compared with non comorbid ‘pure’ MR matched by age and severity of cognitive impairment, it is of interest to search for specific differences in cognitive strengths and challenges and adaptive skills among different mental health syndromes comorbid with MR.

2. Method 2.1. Sample The sample was composed of n = 184 subjects, 103 males (56%) and 81 females (44%), diagnosed as mild (n = 124, 67.4%) or moderate (n = 60, 32.6 %) MR level.

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consent of the participants and/or their families was previously obtained. The procedure was approved by the Ethical Committee of the Scientific Research Institute for Diagnosis and Therapy Oasi (Troina), where the sample was collected.

Age range was 6 years 8 months to 50 years 2 months, mean age 17.1 (standard deviation 7.9). Co-occurring pathologies were schizophrenia, personality disorders, mood disorders, pervasive developmental disorders (PDD), epilepsy and attention deficit hyperactivity disorder (ADHD). The diagnosis of MR and comorbid pathologies was made by a team including psychiatrists and psychologists, according to the criteria of DSM-IV-R (APA, 2000). Table 1 shows the composition of the pathological subgroups and the comparison of the general intelligence levels, not significantly different among the subgroups. The subjects, coming from families with middle/lower social status, were all inpatients in a specialized structure for the diagnosis and the treatment of MR. They were admitted to special school classes and rehabilitative work activities inside the same structure. The study design was included in the assessment procedure routinely done for diagnosis, therefore informed

2.2. Instruments The instruments of the study were WAIS-R (Wechsler adult intelligence scale – revised, Wechsler, 1981) or WISC-R (Wechsler Intelligence Scale for children – revised, Wechsler, 1974), selected according to the chronological age of subjects on the basis of the cut-off age of 16 proposed by Wechsler, and VABS (Vineland Adaptive Behavior Scale – survey form, Sparrow et al., 1984). The tests were administered by qualified psychologists, with several years of practice in the assessment of MR persons. Only complete protocols, i.e., without missing values in any subtest, were considered for the research. Consequently, for each test the number of subjects included in the groups divided according to comorbid pathology may be different. In order to assure the comparability of these subgroups, the absence of significant differences in age levels was previously tested. F-values for the comparison were nonsignificant: for WISC-R sample F[3,95,98] = 1.33 (p = .27), for WAIS-R sample F[3,104,107] = 1.18 (p = .32), for VABS sample F[5,157,162] = 1.58 (p = .17).

Table 1 Sample composition and general intelligence level of the subgroups Syndromes comorbid with MR

General IQ level

Epilepsy ADHD Schizophrenia Personality disorders Mood disorders Pervasive development disorder

N

M (SD)

72 25 15 30 18 24

58.34 55.09 63.73 63.22 56.32 55.09

797

(13.88) (13.24) (11.34) (14.11) (14.46) (13.24)

2.3. Analysis of data To detect the significance of the difference among group’s means, analyses of variance were performed,

ANOVA: F = 1.87, d.f. [5, 178, 183], p = 0.10.

Table 2 Differences in WISC-R subtests between means of subgroups with MR and comorbid pathologies (ages 6–16, n = 99) Subtest

Information Comprehension Arithmetic Similarities Digit span Vocabulary Picture completion Picture arrangement Object assembly Block design Coding Labyrinths

Syndrome comorbid with MR Epilepsy n = 45 M (SD)

ADHD n = 25 M (SD)

Personality disorders n = 17 M (SD)

Mood disorders n = 12 M (SD)

ANOVA d.f. [3, 95, 98] F

7.91 9.24 5.55 7.60 5.03 21.19 13.07 7.57 11.48 10.43 18.12 10.35

5.17 6.13 4.25 5.70 3.89 16.43 10.44 5.92 10.33 6.88 15.33 9.22

9.12 8.71 7.59 8.12 7.38 19.07 14.19 11.33 12.33 14.13 24.36 16.00

7.58 6.36 5.83 6.82 6.44 17.82 11.08 7.82 10.42 8.25 15.25 6.33

3.64* 1.71 2.96* 1.28 4.34** 1.45 0.88 1.58 0.36 2.63* 2.19 3.43*

(4.26) (6.40) (3.69) (4.49) (3.33) (10.87) (11.22) (8.14) (7.25) (9.49) (12.59) (9.93)

(3.24) (4.65) (3.05) (3.70) (3.25) (8.50) (4.55) (6.47) (6.25) (7.25) (10.04) (6.48)

(5.25) (8.15) (3.91) (5.75) (2.90) (6.84) (6.16) (9.67) (7.15) (8.98) (13.59) (8.99)

(3.48) (5.01) (3.66) (4.29) (3.81) (9.17) (4.66) (7.64) (6.01) (6.33) (11.43) (6.22)

Significant Bonferroni post-hoc tests (p < .05): Information: personality disorders > ADHD (t = 3.04). Arithmetic: personality disorders > ADHD (t = 2.97). Digit span: personality disorders > ADHD (t = 3.04). Block design: personality disorders > ADHD (t = 2.70). Labyrinths: personality disorders > mood disorders (t = 2.97). * p < .05. ** p < .01.

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scores, while the lowest scores are found in the ADHD group. Also in block design and labyrinths the highest mean score is recorded for personality disorders, but the lowest mean score is obtained by the mood disorders group. In the test WAIS-R for subjects older than 16 (Table 3) information, comprehension and similarities are the only subtest where differences between the syndromes are statistically significant, schizophrenic MR subjects having the highest mean score, mood disorders and epilepsy the lowest. As regards adaptive behaviors, all the areas of the VABS interview (Table 4) show significant differences among groups with pathologies comorbid with MR. Post-hoc comparisons verify that in all the considered

with Bonferroni post-hoc comparisons, using Systat 10.2 software.

3. Results Analyses of variance show the following differences in subgroups of MR subjects with co-occurrent pathologies. In the test WISC-R, suitable for the ages 6–16, significant differences are found for the subtests information, arithmetic, digit span, block design and labyrinths (Table 2). Post-hoc comparisons show that in the first three subtests, part of the verbal scale, the group of MR with personality disorders has the highest mean

Table 3 Differences in WAIS-R subtests between means of subgroups with MR and comorbid pathologies (ages 17–50, n = 108) Subtest

Syndrome comorbid with MR

Information Comprehension Arithmetic Similarities Digit span Vocabulary Digit-symbol Picture completion Block design Picture arrangement Object assembly

Epilepsy n = 51 M (SD)

Schizophrenia n = 11 M (SD)

Personality disorders n = 30 M (SD)

Mood disorders n = 16 M (SD)

ANOVA d.f. [3, 104, 107] F

4.84 5.96 3.39 5.67 5.71 14.02 15.71 5.96 10.56 7.34 10.06

11.73 9.27 3.91 8.73 6.91 18.64 14.18 7.27 11.64 9.18 11.18

4.50 6.10 3.23 6.40 6.13 13.53 16.03 5.33 11.10 6.69 11.10

3.81 5.50 3.06 4.69 5.63 11.50 12.19 5.19 9.69 7.63 12.00

13.84*** 3.04* 0.39 2.60* 0.73 1.38 0.50 0.82 0.11 0.61 0.29

(3.34) (3.76) (2.11) (3.91) (2.84) (8.89) (11.38) (3.73) (9.24) (5.46) (7.97)

(5.62) (4.29) (2.39) (3.98) (2.34) (8.38) (10.60) (4.31) (9.20) (4.92) (7.01)

(3.42) (2.87) (1.83) (4.23) (2.23) (10.10) (11.43) (3.94) (9.69) (4.48) (7.61)

(2.46) (3.39) (2.46) (3.22) (3.07) (8.25) (10.57) (4.17) (11.10) (6.29) (9.09)

Significant Bonferroni post-hoc tests (p < .05): Information: schizophrenia > epilepsy (t = 5.85), personality disorders (t = 5.85), mood disorders (t = 5.71). Comprehension: schizophrenia > epilepsy (t = 2.81), mood disorders (t = 2.72). Similarities: schizophrenia > mood disorders (t = 2.63). * p < .05. ** p < .01. *** p < .001.

Table 4 Differences in VABS’ areas between means of subgroups with MR and comorbid pathologies (all ages, n = 163) Adaptation area

Communication Daily Living Skills Socialization Motor Skills

Syndrome comorbid with MR Epilepsy

ADHD

Schizophrenia

PDD

Personality disorders

Mood disorders

n = 72 M (SD)

n = 21 M (SD)

n = 15 M (SD)

n = 24 M (SD)

n = 13 M (SD)

n = 18 M (SD)

53.82 68.03 45.31 44.13

55.33 68.10 50.43 46.95

77.73 96.80 59.47 59.62

18.92 35.96 18.17 34.54

73.62 92.00 62.17 58.20

72.88 114.88 71.25 58.75

(31.93) (33.43) (26.17) (15.85)

(19.93) (17.43) (17.66) (13.56)

(25.76) (30.31) (26.22) (11.20)

(9.78) (18.71) (10.61) (11.33)

(29.28) (33.51) (30.94) (12.10)

(24.90) (17.58) (21.23) (10.08)

ANOVA d.f. [5, 157, 162] F 13.76*** 20.12*** 13.23*** 11.44***

Significant Bonferroni post-hoc tests (p < .05): Communication: schizophrenia (t = 7.79), personality disorders (t = 5.93), mood disorders (t = 6.46), ADHD (t = 5.50) epilepsy (t = 5.23) > PDD. Daily living skills: mood disorders > PDD (t = 8.98), epilepsy (t = 6.30), ADHD (t = 5.17), schizophrenia > PDD (t = 6.56), epilepsy (t = 3.59), ADHD (t = 3.01), personality disorders (t = 5.85), epilepsy (t = 4.82), ADHD (t = 3.82) > PDD. Socialization: mood disorders (t = 7.27), personality disorders (t = 5.93), schizophrenia (t = 5.36), ADHD (t = 4.61) epilepsy (t = 4.91) > PDD, mood disorders > epilepsy (t = 4.21). Motor skills: schizophrenia (t = 5.70), mood disorders (t = 5.05), personality disorders (t = 5.00), ADHD (t = 3.02) > PDD, mood disorders (t = 4.03), schizophrenia (t = 3.97), personality disorders (t = 3.39) > epilepsy. *** p < .001.

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variables mentally retarded persons with pervasive development disturbances have the lowest mean scores, epileptics are significantly lower in socialization and motor skills. Significantly higher mean scores are found in mentally retarded subjects with schizophrenia (in the areas of communication and motor skills), and mood disorders (daily living skills and socialization).

4. Discussion It is well known that ADHD, organic diseases as epilepsy, and other psychiatric pathologies as psychotic and mood disorders and pervasive developmental disorders, often coexist with MR, so differential diagnosis has become a priority (Fuller and Sabatino, 1998; Wallander et al., 2003). Our study aimed to find some specific patterns of cognitive ad adaptive skills that differentiate syndromes comorbid with MR. In the cognitive domains, as measured by the subtests of the intelligence scales suitable for the subject’s age, comorbidity is a factor differentiating among mentally retarded subjects. In the developmental ages, both verbal tests requiring memory retrieval (information, arithmetic, digit span) and visuo-spatial tests (block design and labyrinths) are involved as differentiating features. ADHD strongly impairs cognitive performance, while behavioral disorders of mood and thought are less damaging to performance on intellectual tests. In adult samples, the differentiating role of comorbid syndromes is reduced for cognitive skills, and limited to few WAIS-R subtest, i.e., information, comprehension, similarities. These basic verbal abilities of MR individuals are more impaired in mood disorders (i.e., depression), less in schizophrenic disorder. In all ages, the learning and retrieval of cultural knowledge, as measured by information subtest, seems to be the capacity better able to differentiate among various kind of pathology added to RM. Mood disorders are the comorbidity more damaging cognitive skills both for younger and older subjects, perhaps due to lack of motivation and interest in the requested performance. In the earlier ages, also attention deficit disorders impair cognitive processes, delaying reaction times and reducing attentional performance. Comorbidity of schizophrenic and personality and mood disorders impairs less the areas of adaptation and socialization, motor and daily living skills, while these aspects are most damaged, as expected, in pervasive development disturbances. Adaptation scores of ADHD and epileptic MR subjects are intermediate between these extremes. What schizophrenia, personality and mood disorders impact on is not basic adaptive skills but those skills requiring judgment and safety in the community.

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In conclusion, we have to underline the interactions between the outcome of cognitive and psychopathological assessment and the rehabilitation measures. The general goals of the treatment of MR persons with comorbid syndromes are to improve both cognitive and communication skills, to facilitate collaboration between trainers and teachers in order to stimulate MR subject’s integration in school and society, enhancing their cognitive, emotional and relational balance. To plan a more accurate and appropriate rehabilitative treatment, the psychological assessment of dual diagnoses has to refer to the specific underlying components differentiating the comorbid syndromes (Weisblatt, 1994). To this purpose, and to aid clinicians in their daily work, the American Academy of Child and Adolescent Psychiatry proposed some recommendations in the practice parameters for the assessment and treatment of children, adolescents, and adults with MR and comorbid mental disorders (Szymanski and King, 1999). These guidelines, together with the evidence based on empirical studies, may foster more accurate diagnosis and appropriate treatment of the dual diagnosis, essential for the enhancement of the quality of life of the MR persons. As more and more individuals with mental retardation are participating in community life it is important to address attention, mood, and anxiety disorders as these mental health conditions impact both on individual and social functioning and well being.

Acknowledgments Financial support of the study was granted by Ministry of Health, Italy, and Scientific Research Institute for Diagnosis and Therapy IRCSS Oasi, Troina (Italy).

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