Sarah H. Ailey Ph.D. (c), R.N., Beth Marks Ph.D., R.N., Tamar Heller, Ph.D.
Depression, one of the most commonly diagnosed mental illnesses in individuals with intellectual disabilities (ID) (Reiss, 1994), is associated with poor social skills, poor social support, and increases in aggressive behavior (Benson, Reiss, Smith, & Laman, 1985; Laman & Reiss, 1987; Meins, 1993; Reiss & Rojahn, 1993). Behavior problems are a common reason for referral to the mental health system for individuals with ID, and behavior modification models are a prevailing form of mental health treatment for individuals with ID (Spreat & Behar, 1994; Matson & Coe, 1992; Petronko, Harris, & Kormann, 1994). Assessing whether behavior problems are related to underlying problems with depression or other mental health disorders is important in determining effective treatment. In addition, a focus on behavior may mean that individuals with ID who have non-problematic behaviors may not be referred for mental health assessment and treatment, and evaluation of such individuals is important. While our society has moved toward normalization of individuals with ID, depression and its associated problems may hamper the ability of individuals with ID to integrate into community living and working situations.
Instruments useful for measuring depression are needed in research and for screening and diagnostic evaluations (Feinstein, Kaminer, Barrett, & Tylenda, 1988; Jacobson, 1996; Reiss, 1994). Moreover, the use of self-report in research and treatment is limited. The focus of this paper is on the potential use of the adult form of the Childrens Depression Inventory short form (CDI-S [adult-form]) (Kovacs, 1985) as a self-report measure in research and treatment of depression in adults with mild or moderate ID. Two issues are addressed in the usefulness of scores on the CDI-S (adult form) in assessing depression. One issue is whether scores on the self-report CDI-S (adult form) associate to self-report symptoms corresponding Diagnostic and Statistical Manual IV (DSM-IV) (American Psychiatric Association [APA], 1994) criteria for depression. The Psychopathology Instrument for Mentally Retarded Adults affective disorders subscale (PIMRA-AD) is an instrument based on DSM-III (APA, 1980) criteria for depression and is very similar to DSM-IV criteria (APA, 1980, 1994; Kazdin, Matson, & Senatore, 1983). The association of scores on the CDI-S (adult form) to scores on the PIMRA-AD is assessed. The second issue addressed is the item order or endorsability of the CDI-S (adult form), which may give information on how depression is manifested in adults with ID.
The data used in the following discussion are from 73 adults with Down Syndrome who are participants in the Exercise Adherence Study for Adults with Down Syndrome/ Mental Retardation. The Exercise Adherence Study for Adults with Down Syndrome/ Mental Retardation is a research project to assess the effects of a 12-week exercise, nutrition, and health promotion program in adults with Down syndrome and/or mental retardation (Heller & Rimmer, 1999). Participants in the program live in a large urban area, are over 30, and have Down Syndrome and mild to moderate levels of intellectual disability (Heller & Rimmer, 1999). Of the participants, 49% are women, 30% African-American and 7% Hispanic. Depression as assessed by scores on self-report questionnaires is among the variables being measured prior to participation in the program, immediately after participation, and at six month intervals for two years following participation in the program. The data analyzed here come from baseline scores.
Childrens Depression Inventory (CDI-S adult form)
The adult form of the CDI-S is a 10 item scale taken from the 27 item Childrens Depression Inventory (CDI) (Kovacs, 1985; 1992). The CDI is a self-rated depression scale based on the Beck Depression Inventory (BDI) (Kovacs, 1985) and has a second to third grade reading level (Berndt, Schwartz & Kaiser, 1983). Items consist of three statements, with statements for each item scored 0-2. Zero indicates no symptoms of depression and two is the most severe. The CDI -S (adult form) consists of items on sadness, pessimism, self-deprecation, self-hate, crying spells, irritability, negative body image, loneliness, lack of friends, and feeling unloved (Kovacs, 1992).
Psychopathology Instrument for Mentally Retarded Adults affective disorders subscale (PIMRA-AD)
The PIMRA-AD is a checklist of psychopathology symptoms derived directly from Diagnostic and Statistical Manual III (DSM-III) criteria (Kazdin, Matson, & Senatore, 1983; Senatore, Matson, & Kazdin, 1985). The criteria were reworded in simple language (Linaker & Helle, 1994). DSM-III and DSM-IV categorizations of major depression are very similar (APA, 1980, 1995). The affective disorders subscale has seven questions with a yes/no response (Kazdin et al., 1983). The items, scored 1 or 0, indicate presence or absence of symptoms, and are summed to provide a possible score of seven (Kazdin et al., 1983; Senatore et al., 1985). The items consist of sad mood, happy mood, alternating sad and happy moods, weight loss or gain, energy, and enjoyment of being with groups of peoples. Kazdin et al. (1983) recommend categorizing individuals as depressed if responses indicate the presence of sadness and the presence of four or more other symptoms of affective disorders. The criteria established tend to exclude depression less serious than major depression (Linaker & Nitter, 1990). The PIMRA-AD is one of the most widely used instruments in research on depression with individuals with ID.
Rasch psychometric methods are used to evaluate scores on the CDI-S (adult form) and PIMRA-AD for adults with Down syndrome. Rasch psychometric methods are based in Thurstone scaling traditions in which items are not considered to be of equal strength, and positive responses to different items are expected to represent different levels of an attribute. (Nunnally & Bernstein, 1994). In Rasch measurement, item endorsability or order is part of the operational definition of a variable, and assessing item order is related to content and construct validity (Wright & Stone, 1988). Assessing the relation of scores on an instrument to scores on instruments measuring variables thought to be associated is also possible. Using Rasch psychometric methods, a sample of 50 well-targeted persons is conservative to obtain stable estimates (Linacre, 1994).
The mean score on the CDI-S (adult form) with the 73 participants is 4.4 (sd. 4.0), and the mean score on the PIMRA AD is 1.8 (sd 1.4). A cut-off score for referral for the CDI-S (adult form) is 6 (Kovacs, 1992). Twenty-three of the 73 subjects or 32% scored at or above this cutoff. Internal consistency reliability for the CDI using Cronbachs alpha is .54. The test/retest correlation of the CDI-S (adult form) is 0.54 and for the PIMRA-AD is .54. Rasch psychometric methods give separate reliability estimates for persons and for items (Wright & Masters, 1992). Person reliabilities in Rasch measurement are similar to Cronbachs alpha. Person reliability for the CDI-S (adult form) is 0.47 and for the PIMRA-AD is 0.10. Item reliability for the CDI-S (adult form) is 0.91 and for the PIMRA-AD is 0.90. In Rasch measurement separation indices are important. Person separation refers to the ability of test scores to adequately separate persons by their performance. The implication of item separation is that items must be separated enough in difficulty to identify the direction and meaning of the variable. Person separation for the CDI-S (adult form) is 0.94 and item separation is 3.25. Person separation for the PIMRA-AD is 0.34 and item separation is 3.04.
The low person reliabilities and separation indices may be related to lack of variance in the scores of the subjects. As well, the PIMRA-AD is based on DSM criteria of depression. In the approach taken in the DSM criteria of depression, many different symptom patterns could result in the same diagnosis (Clark, Watson, & Reynolds, 1995). A scale for depression can result in two very different score patterns for two individuals. Scores on the instrument may distinguish depressed from non-depressed subjects, but have low internal consistency (Prosser et al., 1998). The item reliability and separation indices indicate that the direction and meaning of the items in the variable of depression can be identified using scores on the instruments.
DSM-IV criteria for depression
Psychological disorders are broadly similar for individuals with mild and moderate intellectual disability and the general population (Sturmey, 1995), and diagnoses based on the DSM-IV criteria are frequently used to determine access to treatment, therapies, and third party payment. Borthwick-Duffy (1994) notes a lack of uniformity in the criteria used for depression and the methods used to determine depression in individuals with ID. One issue in the adequacy of interpretation of scores on depression measures for screening and diagnostic purposes and for research is the ability to identify individuals who meet Diagnostic and Statistical Manual 4th edition (DSM-IV) criteria for depression.
According to the DSM-IV, major depression is defined as episodes lasting at least two weeks in which a person exhibits depressed mood and loss of interest or pleasure in activities along with associated symptoms (APA, 1994). Associated symptoms include decreased energy, appetite changes, sleep disorders, death wishes, mood swings, feelings of worthlessness and guilt, and social withdrawal (APA, 1994). The DSM-IV specifically states that five or more associated symptoms should be present.
DSM-IV criteria for dysthymic disorder are a chronically depressed mood or sadness for at least two years and in which two of the following additional symptoms are present: poor appetite or overeating, insomnia or hypersomnia, low energy or fatigue, low self-esteem, poor concentration or difficulty making decisions, and feelings of hopelessness (p.345). The DSM-IV criteria for the diagnosis of major depression or dysthymic disorder are very similar to those of the DSM-III-R and the DSM-III (APA, 1980; 1991). Individuals with ID may be likely to have sleep loss, poor appetite, and increased fatigue as symptoms of depression (Charlot, Doucette, & Mezzacappa, 1993; Meins, 1993; Marston, Perry, & Roy, 1997). New or increased problem behaviors or episodic behaviors may present as atypical symptoms (Charlot, et al., 1993; Meins, 1993).
Association of CDI-S (adult form) and PIMRA-AD scores
Evaluation of the association of scores on the CDI -S (adult form) with scores on the PIMRA-AD is done as part of establishing whether scores on the CDI-S (adult form) associate with self-reported symptoms reflecting DSM criteria for depression. Scores on the CDI-S (adult form) and the PIMRA-AD were converted to logit scores in Rasch measurement and a Pearson correlation obtained. The correlation of scores on the CDI-S (adult form) with scores on the PIMRA-AD is r=0.42 with statistical significance. The obtained correlation indicates that the two scores are associated. Further, it is also expected that some difference would be seen between the two scores as the CDI-S (adult form) measures cognitive representations of depression and the PIMRA-AD is based on DSM criteria for major depression.
The item structure of the CDI-S (adult form) and PIMRA-AD are evaluated. The authors of the CDI-S (adult form) and the PIMRA-AD do not address the difficulty of endorsement of items. Further, DSM-IV criteria do not address the difficulty of meeting particular criteria as each of the criteria is considered to be of equal weight. Scores on the two scales were combined and item endorsability levels assessed. It should be noted that, in evaluating the response format of the CDI-S (adult form), the middle response with a score of one is transitional (Linacre, 1994). For analysis of the data, the scores of one and two were combined. For example, the score of one on the statement I am sad many times was combined with the score of two on the statement I am sad all the time. The item reflecting loneliness from the CDI-S (adult form) is the easiest item to endorse followed by the items from the CDI-S (adult form) reflecting pessimism, lack of friends, and sadness. Negative endorsement of the item Do you like being with groups of people from the PIMRA-AD and the item reflecting self-hate from the CDI-S (adult form) are the hardest items to endorse.
The findings in this study indicate that improved methods of screening for and diagnosing depression in adults with Down Syndrome and intellectual disability are needed. The individuals participating in the exercise adherence program are not clinically referred, but 32% of the individuals in the study met a cutoff for referral on scores on the CDI-S (adult form).
The findings of the study indicate that simple means of self report of depression such as the CDI-S (adult form) may be useful in research and in diagnosis and treatment of depression in individuals with intellectual disabilities.The usefulness of self-report is an issue in research and treatment of depression for individuals with ID. Discussion regarding self and informant report has sometimes centered on which form of report is better to use (Reiss, 1994). However, in assessing depression, both self and informant reports are useful (Coyne, 1999). The association of scores on the CDI-S (adult form) to scores on the PIMRA-AD, based on DSM criteria, indicates that the CDI-S (adult form) may have usefulness as a self-report supplement to assessing for DSM-IV criteria of depression. Further, the similarity of the CDI-S (adult form) to the BDI, one of the most commonly used instruments to measure depression, may make it useful in comparing and contrasting depression in individuals with ID to the general population. Further research on the sensitivity and specificity of scores on the CDI-S (adult form) in relation to clinical diagnosis may be warranted.
The findings of the study regarding item order endorsement on the CDI-S (adult form) and PIMRA-AD also indicate the need for further investigation of the role of loneliness and lack of friendships in depression and mental health disorders in individuals with ID. The experience of depression has both personal and social effects (Coyne & Calarco, 1995). Self perception is important, and the perception of loneliness and lack of friends is important information in understanding the realities of depression in individuals with Down syndrome and intellectual disabilities. Assessment of social contacts and the social environment may be useful in developing treatment strategies for depression in adults with intellectual disabilities.
Information used in this article comes from a small number of individuals, all of whom have Down syndrome. As well, all the individuals live in an urban area and are clients of agencies that provide sheltered or community employment. Further information is needed from individuals with mild or moderate ID who do not have Down syndrome, do not have employment services, and live in an urban area. The research does indicate the potential usefulness for further investigation regarding using the CDI-S (adult form) as a one means of self-report of depression in research and as part of screening and evaluation of depression in adults with mild and moderate ID.
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Findings for this study are based on data available from the Exercise Adherence Study among adults with Down Syndrome/mental retardation. Heller, T. & Rimmer, J. (1999) Rehabilitation Research and Training Center on Aging with Developmental Disabilities:NIDRR-Grant # H133B980046; Center for Health Promotion Research for People with Disabilities CDC-Grant # CCRS514155; Roybal Center on Health Maintenance NIA Grant # AG15890-12
Correspondence should be addressed to Sarah Ailey, College of Nursing, Rush University, 600 S. Paulina St. #1027A, Chicago, Il. 60612. E-mail is received at firstname.lastname@example.org.