drug addiction and diabetes are two prevalent chronic diseases , and comorbidity of psychiatric disorders with these stress - related diseases is well documented ( 
 1 
  
 7 
 ) . moreover , such comorbidity interferes with the management of these patients ( 
 8 
 ) . oftentimes , evaluating clinicians are faced with considerable confusions for diagnosing comorbid psychiatric disorder in these patients ( 
 5 
 , 
 8 10 
 ) ; therefore , this points a great need to provide proper psychological scales to evaluate and understand such comorbidity in patients with chronic disease ( 
 11 
 ) . nowadays , self - rating assessments have become necessary to advance the clinician in evaluating and understanding psychiatric comorbidities in chronic patients . nevertheless , use of these scales can yield benefits if they are validated ( 
 7 
 , 
 12 
  
 15 
 ) . indeed , validity is the baseline of measurement as a crucial indicator of psychometric quality , and construct validity is essential in these disciplines ( 
 16 
 ) . among valid and reliable self - rating scales , the symptom checklist-90-revised ( scl-90-r ) and general health questionnaire-28 ( ghq-28 ) are both appropriate psychological instruments for assessing psychiatric disorder in chronic patients ( 
 17 
 ) i.e. drug addicts and diabetics . the concurrent validity of the ghq-28 against scl-90-r indicated a meaningful correlation between scores of samples within the scales of these instruments ( 
 18 
 ) . the factor structures of ghq-28 have been consistent with its original dimensions ( 
 18 
  
 22 
 ) ; whereas , the documents for construct validity of the scl-90-r are controversial . the scl-90-r nine subscales are originally proposed as representing a multidimensional structure ( 
 29 
 ) . several studies ( 
 19 
 , 
 23 
  
 29 
 ) replicated the construct validity of scl-90-r , and supported the multidimensional structure of the scl-90-r ; meanwhile , other studies failed to replicate this fact , and suggested a unitary measure for global distress instead of multi - dimensional measure ( 
 19 
 , 
 23 
 , 
 30 
  
 34 
 ) . although , the resent study done in malaysia revealed a good reliability for the scl-90-r ( 
 35 
 ) ; yet , there is no study has examined the construct validity of this self - report inventory in malaysia . with regard to the contributions of psychological assessments in case finding , case conceptualization , and treatment planning of patients with comorbid psychiatric disorders ( 
 18 
 , 
 36 
 ) , validation of the scl-90-r and ghq-28 would be important to ensure accurate psychiatric information especially in patients with stress - related disease like drug addiction and diabetes . furthermore , continual improvement and innovation in validating such scales is necessary to all research settings ; in fact , they must be replicated in different setting , language , and culture , it is because , they rely on the judgment of the respondents , and are sensitive to the linguistic or cultural factors ( 
 34 
 ) . despite the significance of studying the psycho - metric properties of psychological instruments , there do not appear to be any study investigating the construct of scl-90-r and ghq-28 scales in malaysia . therefore , the aim of this study was to investigate the constructs ( convergent and discriminant validity ) of scl- 90-r and ghq-28 scales in chronic patients ( i.e. drug addiction and diabetes ) and normal population in malaysia . this study would be a step toward establishing the construct validity of the malaysian version the scl-90-r and ghq-28 , and add substantial information on the construct validity of scl-90-r and ghq-28 . furthermore , the present study advances the literature through the comparative investigation of the mentioned scales . this comparative cross - sectional study was carried out in kuala lumpur , malaysia in 201213 . the sample frame consisted of malaysian adults aged 18 and above with chronic disease and normal people as a control group . the clinical samples were patients with drug addiction and diabetes ( two prevalent stress - related diseases ) , and were recruited from six clinics , including three diabetic clinics and three rehabilitation clinics . the non - clinical sample was consisted of the normal people free of any chronic disease , and was selected nearby the selected clinics in the study . with regard to the results of sample size calculations , a total of 660 subjects were included in the study through simple random sampling method . the method of calculation for the sample size was the method described by kelsey et al . the following subjects have been excluded in this study ( the registration criteria ) : 
 females : to prevent the gender bias , the females were excluded from the study populations , as only 12 females mmt patients referred to the clinics.non-malaysian citizens ( for the purpose of homogeneity).those unwilling to answer the questionnaire.severe ill patients or who needed to be referred to emergency room.those with communication difficulties ; e.g. deafness , blindness , muteness , or dysarthria . 
  females : to prevent the gender bias , the females were excluded from the study populations , as only 12 females mmt patients referred to the clinics . non - malaysian citizens ( for the purpose of homogeneity ) . those unwilling to answer the questionnaire . severe ill patients or who needed to be referred to emergency room . those with communication difficulties ; e.g. deafness , blindness , muteness , or dysarthria . adding to exclusions , to obtain accurate data , if any patient revealed any withdrawal symptoms , acute intoxication , or acute psychosis would be excluded from the study , and also if he had an organic brain problem , or an organic brain problem made it difficult for giving reliable information , he would be excluded , as well . prior to collect the data , the ethical approval was obtained from the medical ethics committee of university of malaya medical center ( ummc ) . the ethical conditions of participation including voluntary participation , privacy , anonymity and confidentiality were explained to the respondents . based on the written informed consent , they would be free to withdraw from the study at any point . all subjects in this study declared their agreement , and to ensure anonymity , they were mentioned that putting their names or other identifying notation on the questionnaires is optional . afterward , they were invited to complete the screening package translated to the bahasa malaysian . the instruments applied in this study were the bahasa malaysian version of symptom checklist-90-riviesed ( scl-90-r ) and general health questionnaire-28 items ( ghq-28 ) . these scales were designed to determine the mental health status and psychiatric symptoms at a specific time . they are brief instruments being sensitive , time efficient and well - validated for assessing common psychiatric disorders ( 
 38 
 ) , and are successfully used in both clinical and epidemiological studies of mental disorders ( 
 18 
 , 
 39 
 , 
 40 
 ) . the scl-90-r developed by derogatis is a self - report instrument containing 90 items and designed to measure nine current psychiatric symptoms , as well as psychological distress . the scl-90-r sub - scales assess followings psychiatric symptoms : somatization , obsessive compulsive disorder , interpersonal sensitivity , depression , anxiety , hostility , phobic anxiety , paranoid ideation , and psychoticism . each item has five following response categories : 0 = not at all , 1= little , 2 = some , 3 = very , 4 = severe . albeit this instrument has been developed in 1970 's , it is still useful to understand psychiatric disorder as classified in dsm - iv ( 
 28 
 ) . the scale helps measuring 4 groups of psychiatric morbidity containing somatization , anxiety , social dysfunction , and depression , and provides overall mental health at a specific point in time , as well . each item has four response categories such as  better than usual  ;  same as usual  ;  worse than usual  ; or  much worse than usual  . the higher ghq-28 scores , the severe psychiatric disorder in which the subject may suffer from . the data was analyzed using statistical package for the social sciences software ( spss ) version 20 , and those with more than 20% missing data were excluded . the confirmatory factor analysis ( cfa ) and convergent and discriminant validity of the constructs were examined by the following indexes : composite reliability ( cr ) , average variance extracted ( ave ) , maximum shared squared variance ( msv ) , and average shared squared variance ( asv ) . pearson correlation was utilized to prove the relationship between the research instruments , as well as their dimensions . this comparative cross - sectional study was carried out in kuala lumpur , malaysia in 201213 . the sample frame consisted of malaysian adults aged 18 and above with chronic disease and normal people as a control group . the clinical samples were patients with drug addiction and diabetes ( two prevalent stress - related diseases ) , and were recruited from six clinics , including three diabetic clinics and three rehabilitation clinics . the non - clinical sample was consisted of the normal people free of any chronic disease , and was selected nearby the selected clinics in the study . with regard to the results of sample size calculations , a total of 660 subjects were included in the study through simple random sampling method . the method of calculation for the sample size was the method described by kelsey et al . the following subjects have been excluded in this study ( the registration criteria ) : 
 females : to prevent the gender bias , the females were excluded from the study populations , as only 12 females mmt patients referred to the clinics.non-malaysian citizens ( for the purpose of homogeneity).those unwilling to answer the questionnaire.severe ill patients or who needed to be referred to emergency room.those with communication difficulties ; e.g. deafness , blindness , muteness , or dysarthria . 
  females : to prevent the gender bias , the females were excluded from the study populations , as only 12 females mmt patients referred to the clinics . non - malaysian citizens ( for the purpose of homogeneity ) . those unwilling to answer the questionnaire . severe ill patients or who needed to be referred to emergency room . those with communication difficulties ; e.g. deafness , blindness , muteness , or dysarthria . adding to exclusions , to obtain accurate data , if any patient revealed any withdrawal symptoms , acute intoxication , or acute psychosis would be excluded from the study , and also if he had an organic brain problem , or an organic brain problem made it difficult for giving reliable information , he would be excluded , as well . prior to collect the data , the ethical approval was obtained from the medical ethics committee of university of malaya medical center ( ummc ) . the ethical conditions of participation including voluntary participation , privacy , anonymity and confidentiality were explained to the respondents . based on the written informed consent , they would be free to withdraw from the study at any point . all subjects in this study declared their agreement , and to ensure anonymity , they were mentioned that putting their names or other identifying notation on the questionnaires is optional . afterward , they were invited to complete the screening package translated to the bahasa malaysian . the instruments applied in this study were the bahasa malaysian version of symptom checklist-90-riviesed ( scl-90-r ) and general health questionnaire-28 items ( ghq-28 ) . these scales were designed to determine the mental health status and psychiatric symptoms at a specific time . they are brief instruments being sensitive , time efficient and well - validated for assessing common psychiatric disorders ( 
 38 
 ) , and are successfully used in both clinical and epidemiological studies of mental disorders ( 
 18 
 , 
 39 
 , 
 40 
 ) . the scl-90-r developed by derogatis is a self - report instrument containing 90 items and designed to measure nine current psychiatric symptoms , as well as psychological distress . the scl-90-r sub - scales assess followings psychiatric symptoms : somatization , obsessive compulsive disorder , interpersonal sensitivity , depression , anxiety , hostility , phobic anxiety , paranoid ideation , and psychoticism . each item has five following response categories : 0 = not at all , 1= little , 2 = some , 3 = very , 4 = severe . albeit this instrument has been developed in 1970 's , it is still useful to understand psychiatric disorder as classified in dsm - iv ( 
 28 
 ) . the scale helps measuring 4 groups of psychiatric morbidity containing somatization , anxiety , social dysfunction , and depression , and provides overall mental health at a specific point in time , as well . each item has four response categories such as  better than usual  ;  same as usual  ;  worse than usual  ; or  much worse than usual  . the higher ghq-28 scores , the severe psychiatric disorder in which the subject may suffer from . the scl-90-r developed by derogatis is a self - report instrument containing 90 items and designed to measure nine current psychiatric symptoms , as well as psychological distress . the scl-90-r sub - scales assess followings psychiatric symptoms : somatization , obsessive compulsive disorder , interpersonal sensitivity , depression , anxiety , hostility , phobic anxiety , paranoid ideation , and psychoticism . each item has five following response categories : 0 = not at all , 1= little , 2 = some , 3 = very , 4 = severe . albeit this instrument has been developed in 1970 's , it is still useful to understand psychiatric disorder as classified in dsm - iv ( 
 28 
 ) . the scale helps measuring 4 groups of psychiatric morbidity containing somatization , anxiety , social dysfunction , and depression , and provides overall mental health at a specific point in time , as well . each item has four response categories such as  better than usual  ;  same as usual  ;  worse than usual  ; or  much worse than usual  . the higher ghq-28 scores , the severe psychiatric disorder in which the subject may suffer from . the data was analyzed using statistical package for the social sciences software ( spss ) version 20 , and those with more than 20% missing data were excluded . the confirmatory factor analysis ( cfa ) and convergent and discriminant validity of the constructs were examined by the following indexes : composite reliability ( cr ) , average variance extracted ( ave ) , maximum shared squared variance ( msv ) , and average shared squared variance ( asv ) . pearson correlation was utilized to prove the relationship between the research instruments , as well as their dimensions . the entire sample fully completed the malaysian versions of ghq-28 ( bm ) and scl-90-r ( bm ) in the study . the mean age of the study sample was 40.45 ( sd = 10.735 ) , and the majority of them were malay ( 78.9% ) , muslim ( 79.2% ) . result of the present study is based on goodness of fit of the measurement models obtained for both scales by using amos-21 . indeed , the measurement model was adjusted to provide a few useful indexes putting to test the construct validity and reliability of the ghq-28 and scl-90-r . the measurement model showed satisfactory fit statistics ; ( chi - squared=810.8 , df=305 , rmr=.023 , cfi= .962 , agfi= .898 , gfi= .918 , rmsea=0.05 ) . to measure the consistency of related questions in the ghq-28 , the subscales of the scale were subjected to reliability analysis . according to the results of composite reliability ( cr ) , the composite reliability of ghq-28 subscales ranged from 0.915 to 0.859 , accordingly , the highest consistency was related to somatization items ( 0.915 ) , and the lowest consistency was related to depression items ( 0.85 ) ; thus , the reliability of the scale was established . following confirmatory factor analysis ( cfa ) and determining the measurement model the construct validity was evaluated to calculate the discriminant and convergent validity of the subscales . all variables have met a sufficient convergent validity in the study ; indeed , composite reliability ( cr ) is between 0.875 and 0.915 in the study , and the standardized factor loadings are significant ; likewise , as illustrated in 
 table 1 
 , composite reliabilities ( cr ) of all dimensions have exceeded the minimum limit ( 0.70 ) , as well as the average variance extracted ( ave ) . furthermore , ave is all above the acceptable threshold level ( 0.50 ) implying that greater than fifty percent of the variances have been observed . convergent and discriminant validity of ghq-28 composite reliability ( cr ) , average variance extracted ( ave ) , maximum shared squared variance ( msv ) , and average shared squared variance ( asv ) to obtain discriminant validity , the maximum shared squared variances ( msv ) has been compared between factors and average shared squared variance ( asv ) as well as average variance extracted ( ave ) . indeed , the discriminant validity was obtained by putting to test the average variance extracted for all construct against squared correlations ( shared variance ) between the construct and all other constructs in the model . as all of the constructs have exceeded the test , the discriminant validity has been confirmed in the current study . furthermore , ave squared root of each dimension surpassed the squared correlation between two dimensions suggesting that an adequate discriminant validity for all of the constructs ( 
 table 2 
 ) . construct correlation matrix note : correlations are below the diagonal and ave is presented on the diagonal , in bold the measurement model showed satisfactory fit statistics ( chi - squared = 12587 , df = 3265 , rmr = 0.038 , cfi = 0.785 , agfi = 0.636 , gfi = 0.656 , rmsea = 0.06 ) . to measure the consistency of related questions in the ghq-28 composite reliability index revealed that all factor loadings of the scale were significant and greater than 0.50 level , and the consistency of the scl-90-r was in a high acceptable level ( 

 table 3 

 ) in which the consistency of its subscales ranged from 0.955 to 0.904 , the highest consistency was related to the anxiety items ( 0.955 ) , and the lowest consistency was related to aggression items ( 0.904 ) . therefore , the reliability of the questionnaire was established , as well . convergent and discriminant validity of scl-90 composite reliability ( cr ) , average variance extracted ( ave ) , maximum shared squared variance ( msv ) , and average shared squared variance ( asv ) . scl_71 and scl_60 had a loading factor > 0.5 and were excluded from the analysis on the basis of the cfa and measurement model the scl90-r was evaluated for construct validity ( 
 table 3 
 ) ; a sufficient convergent validity have been provided for all variables . the results show that composite reliability ( cr ) for all dimensions are above 0.9 and also are larger than the ave . estimated ave were all above the acceptable threshold 0.5 , suggesting that greater than one - half of the variances observed . msv and asv were larger than ave for scl-90-r dimensions ; thus , the discriminant validity was not met for this questionnaire . based on 
 table 4 
 , the squared root of ave of each dimension is less than the correlations between two dimensions . thus , for all of the constructs the discriminant validity is not adequate . construct correlation matrix note : correlations are below the diagonal , and ave is presented on the diagonal , in bold pearson correlation coefficient was utilized for evaluation of the relationship between total mean scores of the ghq-28 and scl-90-r as well as their common subscales including ; somatization , anxiety , and depression . the relationships were significantly positive ; total mean scores ( r= 0,765 p<0.01 ) , somatization ( r=0.671 , p<0.01 ) , anxiety ( r=0.728 , p<0.01 ) , and depression ( r=0.660 , p<0.01 ) . the measurement model showed satisfactory fit statistics ; ( chi - squared=810.8 , df=305 , rmr=.023 , cfi= .962 , agfi= .898 , gfi= .918 , rmsea=0.05 ) . to measure the consistency of related questions in the ghq-28 , the subscales of the scale were subjected to reliability analysis . according to the results of composite reliability ( cr ) , the composite reliability of ghq-28 subscales ranged from 0.915 to 0.859 , accordingly , the highest consistency was related to somatization items ( 0.915 ) , and the lowest consistency was related to depression items ( 0.85 ) ; thus , the reliability of the scale was established . following confirmatory factor analysis ( cfa ) and determining the measurement model the construct validity was evaluated to calculate the discriminant and convergent validity of the subscales . all variables have met a sufficient convergent validity in the study ; indeed , composite reliability ( cr ) is between 0.875 and 0.915 in the study , and the standardized factor loadings are significant ; likewise , as illustrated in 
 table 1 
 , composite reliabilities ( cr ) of all dimensions have exceeded the minimum limit ( 0.70 ) , as well as the average variance extracted ( ave ) . furthermore , ave is all above the acceptable threshold level ( 0.50 ) implying that greater than fifty percent of the variances have been observed . convergent and discriminant validity of ghq-28 composite reliability ( cr ) , average variance extracted ( ave ) , maximum shared squared variance ( msv ) , and average shared squared variance ( asv ) to obtain discriminant validity , the maximum shared squared variances ( msv ) has been compared between factors and average shared squared variance ( asv ) as well as average variance extracted ( ave ) . indeed , the discriminant validity was obtained by putting to test the average variance extracted for all construct against squared correlations ( shared variance ) between the construct and all other constructs in the model . as all of the constructs have exceeded the test , the discriminant validity has been confirmed in the current study . furthermore , ave squared root of each dimension surpassed the squared correlation between two dimensions suggesting that an adequate discriminant validity for all of the constructs ( 
 table 2 
 ) . construct correlation matrix note : correlations are below the diagonal and ave is presented on the diagonal , in bold the measurement model showed satisfactory fit statistics ( chi - squared = 12587 , df = 3265 , rmr = 0.038 , cfi = 0.785 , agfi = 0.636 , gfi = 0.656 , rmsea = 0.06 ) . to measure the consistency of related questions in the ghq-28 composite reliability index revealed that all factor loadings of the scale were significant and greater than 0.50 level , and the consistency of the scl-90-r was in a high acceptable level ( 

 table 3 

 ) in which the consistency of its subscales ranged from 0.955 to 0.904 , the highest consistency was related to the anxiety items ( 0.955 ) , and the lowest consistency was related to aggression items ( 0.904 ) . therefore , the reliability of the questionnaire was established , as well . convergent and discriminant validity of scl-90 composite reliability ( cr ) , average variance extracted ( ave ) , maximum shared squared variance ( msv ) , and average shared squared variance ( asv ) . scl_71 and scl_60 had a loading factor > 0.5 and were excluded from the analysis on the basis of the cfa and measurement model the scl90-r was evaluated for construct validity ( 
 table 3 
 ) ; a sufficient convergent validity have been provided for all variables . the results show that composite reliability ( cr ) for all dimensions are above 0.9 and also are larger than the ave . estimated ave were all above the acceptable threshold 0.5 , suggesting that greater than one - half of the variances observed . msv and asv were larger than ave for scl-90-r dimensions ; thus , the discriminant validity was not met for this questionnaire . based on 
 table 4 
 , the squared root of ave of each dimension is less than the correlations between two dimensions . thus , for all of the constructs the discriminant validity is not adequate . construct correlation matrix note : correlations are below the diagonal , and ave is presented on the diagonal , in bold pearson correlation coefficient was utilized for evaluation of the relationship between total mean scores of the ghq-28 and scl-90-r as well as their common subscales including ; somatization , anxiety , and depression . the relationships were significantly positive ; total mean scores ( r= 0,765 p<0.01 ) , somatization ( r=0.671 , p<0.01 ) , anxiety ( r=0.728 , p<0.01 ) , and depression ( r=0.660 , p<0.01 ) . the current study aimed to examine the construct validity of the malaysian version of ghq-28 and scl-90-r as two psychometric scales in two clinical sample , as well as normal sample . following the measurement model and confirmatory factor analysis ( cfa ) , convergent and discriminant validity of both scales were evaluated . 
  on the basis of confirmatory factor analysis , all dimensions of the malaysian version of ghq-28 and scl-90-r scales had sufficient internal consistency ( 
 table 1 
 and 
 3 ) which implies a sufficient reliability and convergent validity for psychometric testing . in the other words , the results generally pointed that almost all items of the scales were significantly correlated with the factors ( symptoms ) of the original versions . therefore , the finding of the study replicated those confirmed the convergent validity of the ghq-28 ( 
 19 
  
 22 
 , 
 41 
 ) , as well as the scl-90-r ( 
 19 
 , 
 23 
  
 27 
 ) . on the basis of confirmatory factor analysis , the index value for all constructs has indicated no concerns about the construct validity of the ghq-28 and support the four - factor structure of the scale . putting simple terms , the sample of study could recognize inter - correlation between items or recognize the similarities among items ; likewise , they could distinguish the differences between items , suggesting an adequate discriminant validity . accordingly , the finding of the study is consistent with previous studies supporting construct validity and reliability of this scale ( 
 19 
  
 22 
 , 
 41 
 ) ; however , it is inconsistent with another study ( 
 17 
 ) . in contrast , this study failed to support the construct validity of the scl-90-r , in fact discriminant validity was not sufficient . technically , ave for all dimensions was less than msv and asv , in addition , squared root of ave is less than the correlation between two constructs ( 
 table 3 
 ) . the scl-90-r subscales are originally proposed to represent a nine - factor structure ; however , the confirmatory factor analysis failed to support this fact ; therefore , the study failed to support the multidimensionality of the scale with a stable multi - factor structure . it may be assumed that this assessment tool is more useful as a unitary measure for global distress instead of multidimensional measure ( 
 32 
 ) . nonetheless , the study supported the previous studies suggesting the scl-90-r as a unitary measure rather than multidimensional structure ( 
 19 
 , 
 23 
 , 
 30 
  
 34 
 ) , and was inconsistent with those studies replicated the multidimensionality of the original version of this scale ( 
 19 
 , 
 23 
  
 28 
 ) . however , the current finding lends further support of the limits of the scl-90-r as reported elsewhere ( 
 19 
 , 
 25 
 , 
 32 
 ) . one way may account for is , the scores of the scl-90-r are subjected to response biases , and severity and acuteness of mental crisis is offered as an explanation . putting simple terms , some respondents believe that reporting their severe psychopathology such as paranoid status , hostility , and psychotic symptoms are undesirable and may lead to view of the involuntary hospitalization or other probable adverse consequences such as social and working problems . therefore , a positive response bias , that is , denying and underreporting with the aim of preventing the probable adverse consequences would lessen the variability of the scores leading to incline toward favor of a general psychopathology factor . another reason could be due to the relationships between the sub - scales of the scl-90-r . for example , interpersonal sensitivity is associated with anxiety ( 
 42 
 ) , and also depression is associated with somatization ( 
 43 
 ) . finally , the factor structure of the scl-90-r may vary throughout the time of observation in different sample ( 
 32 
 ) . yet on the bias of confirmatory factor analysis , the construct validity of the malaysian version of ghq-28 has been confirmed in the current study ; however , this study failed to do so with the scl-90-r . since the scl-90-r nine subscales are originally proposed as representing a multi - dimensional structure , this study failed to replicate this fact , and suggested a unitary measure for global distress instead of multi - dimensional measure ; thus , it can be argued that multidimensionality of the scl-90-r as clinical purposes is questionable . therefore , it is may be a better unitary measure for assessing psychological status , general distress , and screening for mental disorders , as well as measuring change in outcome studies . further research need to be carried out to prove this finding . this study might be considered unique , for , no study has focused on construct validity of the malaysian version of the ghq-28 and scl-90-r across three different samples simultaneously ; therefore , it may be contributed to add knowledge to the utility of two widely used psychological assessment tools . ethical issues ( including plagiarism , informed consent , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc . ) have been completely observed by the authors .
background : given that validity is the baseline of psychological assessments , there is a need to provide evidence - based data for construct validity of such scales to advance the clinicians for evaluating psychiatric morbidity in psychiatric and psychosomatic setting.methods:this comparative cross - sectional study aimed to investigate the construct validity of the malaysian version of the ghq-28 and the scl-90-r . 
 the sample comprised 660 individuals including diabetics , drug dependents , and normal population . 
 the research scales were administered to the participants . 
 convergent and discriminant validity of both scales were investigated by confirmatory factor analysis ( cfa ) using amos . 
 the pearson correlation coefficient was utilized to obtain the relationship between the two scales.results:the internal consistency of the ghq-28 and scl-90-r were highly acceptable , and confirmatory factor analysis confirmed the convergent validity of both scales . 
 the results of this study revealed that the construct validity of ghq-28 was acceptable , whereas discriminant validity of scl-90-r was not adequate . according to pearson correlation coefficient 
 the relationships between three common subscales of the ghq-28 and scl-90-r were significantly positive ; somatization ( r=0.671 , p<0.01 ) , anxiety ( r=0.728 , p<0.01 ) , and depression ( r=0.660 , p < 0.01).conclusions : this study replicated the construct of the malaysian version of ghq-28 , yet failed to support the nine - factor structure of the scl-90-r . 
 therefore , multidimensionality of the scl-90-r as clinical purposes is questionable , and it may be a better unitary measure for assessing and screening mental disorders . further research need to be carried out to prove this finding .