the present study utilized an experimental design via pre - test and post - test in three groups .
the participants were selected from the child psychiatry clinic of ibn - e - sina psychiatric hospital in mashhad using convenience sampling .
this sample size was calculated using g power software version 3.1 with alpha = 0.05 and a high effect size based on the study of klingberg et al . ( 47 ) .
inclusion and exclusion criteria were as follows : 
 inclusion criteria : 1-children aged 6 to 12 years ; 2- diagnosis of adhd based on the dsm - tr criteria by a child and adolescent psychiatrist ; 3- taking ritalin and 4-having normal iq score ; 4- signing the consent form by mothers.exclusion criteria : 1-children who were taking any other medications were excluded from the study .
inclusion criteria : 1-children aged 6 to 12 years ; 2- diagnosis of adhd based on the dsm - tr criteria by a child and adolescent psychiatrist ; 3- taking ritalin and 4-having normal iq score ; 4- signing the consent form by mothers .
exclusion criteria : 1-children who were taking any other medications were excluded from the study .
the present sample was randomly assigned into three research groups as follows : 1 ) parent training group for 12 mothers ; 2 ) working memory group consisting of 12 children ; 3 ) the combined group comprising 12 children along with their mothers . in this group , children benefited from working memory training and their mothers participated in parent training sessions . parent and working memory trainings were conducted by a clinician with a masters degree and supervised by a phd in child psychology .
the participants of the three groups were concurrently under medication that was the same ( ritalin ) for all the subjects .
also , the dosage of the medication was similar in all the participants according to their weight , so the three groups were homogeneous in this respect . to collect the required data , the present study employed the following instruments : the snap - iv is a revision of the swanson , nolan and pelham ( snap ) questionnaire ( 61 ) .
the items from the dsm - iv criteria for attention deficit hyperactivity disorder ( adhd ) are included for the two following subsets of symptoms : inattention ( items 1 to 0 ) and hyperactivity / impulsivity ( items 10 to 18 ) .
scoring procedure is as follows : each item is scored on a likert - scale type ranging 0 - 3 ( never = 0 , sometimes = 1 , often = 2 , always = 3 ) .
the total score is then divided by 18 and each subtype is divided by 9 . to determine the cut - off point , the designers of the scale utilized mean and standard deviation of 1.65(61 , 62 ) .
( 1386 ) estimated the total cut - off point and the cut - off point of the subtypes of adhd - i and adhd - h as 1.57 , 1.1 , and 1.9 , respectively .
the total reliability of the scale and the reliability of the subscales calculated via cronbach s alpha were found to be 0.97 , 0.90 , 0.76 , respectively , ( 62 ) . in a similar vein , sadroaldin et al . , ( 1386 ) reported the reliability estimates of the scale calculated via test - retest , cronbach s alpha and split - half reliability coefficients among a sample of iranian children as 0.82 , 0.90 , and 0.76 , respectively ( 63 ) .
this scale was utilized in the present study as a diagnostic test as well as pre - test and post - test to study the decline of the symptoms .
child behavior checklist ( cbcl ) which is appropriate for children within the age range of 6 - 18 years is completed by the parents according to the participant s condition over the preceding six months .
cbcl comprises three sections : a ) demographic information ; b ) competence and adaptive functioning criteria ; c ) dsm and experience - based scales .
each item is rated on a scale ranging from 0 ( not true ) , to 1 ( somehow true ) and 2 ( totally or often true ) . the total reliability of the instrument estimated via cronbach s alpha was 0.97 and it was 0.94 via test - retest .
minaee s ( 1385 ) study demonstrated that cronbach s alpha estimated for competence and adaptive functioning ranged from 0.65 to 0.91 , cronbach s alpha calculated for dsm was acceptable and ranged from 0.62 to 0.92 .
cronbach s alpha computed for the subscales of adhd in each form was found to be between 0.92 and 0.78 .
it is worth mentioning that cbcl was employed in the present study in order to diagnose the patients and examine the reduction of the symptoms of adhd .
. these interviews can vary by the objective , structure and source of data collection ( 66 ) . in the present study ,
the diagnostic clinical interviews based on dsm - iv - tr criteria were conducted by a child and adolescent psychiatrist .
working memory training software was designed by khodadady , mashhadi and amani ( 1388 ) ; compatible with its english version made by the cogmed company , this software in a form of a computer game presents different tasks to improve the visual and auditory working memory ( 67 ) . the current version , the wisc - iv , was produced in 2003 .
the wisc - iv is divided into fifteen subtests , ten of which formed a part of the previous wisc iii .
the five new subtests include three core tests : picture concepts , letter - number sequencing , matrix reasoning and two supplemental tests : cancellation and word reasoning .
the wisc - iv generates a full scale iq ( fsiq ) which represents overall cognitive ability .
the four other composite scores are verbal comprehension index ( vci ) , perceptual reasoning index ( pri ) , processing speed index ( psi ) and working memory index ( wmi).some studies were conducted to examine the scale s reliability and validity in iran .
there was a significant correlation between wisc - iv , raven s progressive matrices and wisc  ii ( 68 , 69 ) .
the present study was conducted in several phases . in the first phase , after the diagnosis was made by a child and adolescent psychiatrist , snap - iv rating scale and cbcl test were completed by the mother . in the second phase , the wechsler intelligence scale for children - fourth edition
was implemented in order to homogenize the groups in terms of their iqs and to examine whether the participants had any intelligence incompetency .
the third phase included the random assignment of the participants in the treatment groups and the onset of the treatment .
after conducting the pre - tests , the training program derived from the barkley s model was offered to the parent training group over eight private sessions .
the training issues consisted of the following 10 steps : 
 step 1 : introducing adhd and presenting an overviewstep 2 : understanding parent - child relationshipstep 3 : improving positive attention skillsstep 4 : developing positive attention skills and enhancing child acceptancestep 5 : creating a coupon - based economy at homestep 6 : supplementing response coststep 7 : using timeoutstep 8 : managing children s behaviour in public placesstep 9 : making preparations for restraining school problemsstep 10 : back - up sessions step 1 : introducing adhd and presenting an overview step 2 : understanding parent - child relationship step 3 : improving positive attention skills step 4 : developing positive attention skills and enhancing child acceptance step 5 : creating a coupon - based economy at home step 6 : supplementing response cost step 7 : using timeout step 8 : managing children s behaviour in public places step 9 : making preparations for restraining school problems step 10 : back - up sessions during the last session , snap - iv rating scale and cbcl test were completed again by mothers . in the working memory training group , after performing pre - tests , children were required to take part in individual sessions .
besides , visual and auditory computer - based rewards encouraged the child to sustain his / her effort . at the end of the eighth training session , the post - tests were performed . in the combined group , after completing the pre - tests , both trainings were concurrently presented for the mother and her child .
post - test was performed in the last session . before testing the research hypotheses ,
the wisc - iv intelligence test was conducted to ensure the homogeneity of the participants regarding their intelligence level .
the present study utilized an experimental design via pre - test and post - test in three groups .
the participants were selected from the child psychiatry clinic of ibn - e - sina psychiatric hospital in mashhad using convenience sampling .
this sample size was calculated using g power software version 3.1 with alpha = 0.05 and a high effect size based on the study of klingberg et al . ( 47 ) .
inclusion and exclusion criteria were as follows : 
 inclusion criteria : 1-children aged 6 to 12 years ; 2- diagnosis of adhd based on the dsm - tr criteria by a child and adolescent psychiatrist ; 3- taking ritalin and 4-having normal iq score ; 4- signing the consent form by mothers.exclusion criteria : 1-children who were taking any other medications were excluded from the study .
inclusion criteria : 1-children aged 6 to 12 years ; 2- diagnosis of adhd based on the dsm - tr criteria by a child and adolescent psychiatrist ; 3- taking ritalin and 4-having normal iq score ; 4- signing the consent form by mothers .
exclusion criteria : 1-children who were taking any other medications were excluded from the study .
the present sample was randomly assigned into three research groups as follows : 1 ) parent training group for 12 mothers ; 2 ) working memory group consisting of 12 children ; 3 ) the combined group comprising 12 children along with their mothers . in this group , children benefited from working memory training and their mothers participated in parent training sessions . parent and working memory trainings were conducted by a clinician with a masters degree and supervised by a phd in child psychology .
the participants of the three groups were concurrently under medication that was the same ( ritalin ) for all the subjects .
also , the dosage of the medication was similar in all the participants according to their weight , so the three groups were homogeneous in this respect .
to collect the required data , the present study employed the following instruments : the snap - iv is a revision of the swanson , nolan and pelham ( snap ) questionnaire ( 61 ) .
the items from the dsm - iv criteria for attention deficit hyperactivity disorder ( adhd ) are included for the two following subsets of symptoms : inattention ( items 1 to 0 ) and hyperactivity / impulsivity ( items 10 to 18 ) .
scoring procedure is as follows : each item is scored on a likert - scale type ranging 0 - 3 ( never = 0 , sometimes = 1 , often = 2 , always = 3 ) .
the total score is then divided by 18 and each subtype is divided by 9 . to determine the cut - off point , the designers of the scale utilized mean and standard deviation of 1.65(61 , 62 ) .
( 1386 ) estimated the total cut - off point and the cut - off point of the subtypes of adhd - i and adhd - h as 1.57 , 1.1 , and 1.9 , respectively .
the total reliability of the scale and the reliability of the subscales calculated via cronbach s alpha were found to be 0.97 , 0.90 , 0.76 , respectively , ( 62 ) . in a similar vein , sadroaldin et al . , ( 1386 ) reported the reliability estimates of the scale calculated via test - retest , cronbach s alpha and split - half reliability coefficients among a sample of iranian children as 0.82 , 0.90 , and 0.76 , respectively ( 63 ) .
this scale was utilized in the present study as a diagnostic test as well as pre - test and post - test to study the decline of the symptoms .
child behavior checklist ( cbcl ) which is appropriate for children within the age range of 6 - 18 years is completed by the parents according to the participant s condition over the preceding six months .
cbcl comprises three sections : a ) demographic information ; b ) competence and adaptive functioning criteria ; c ) dsm and experience - based scales .
each item is rated on a scale ranging from 0 ( not true ) , to 1 ( somehow true ) and 2 ( totally or often true ) .
the total reliability of the instrument estimated via cronbach s alpha was 0.97 and it was 0.94 via test - retest .
minaee s ( 1385 ) study demonstrated that cronbach s alpha estimated for competence and adaptive functioning ranged from 0.65 to 0.91 , cronbach s alpha calculated for dsm was acceptable and ranged from 0.62 to 0.92 .
cronbach s alpha computed for the subscales of adhd in each form was found to be between 0.92 and 0.78 .
it is worth mentioning that cbcl was employed in the present study in order to diagnose the patients and examine the reduction of the symptoms of adhd .
. these interviews can vary by the objective , structure and source of data collection ( 66 ) . in the present study ,
the diagnostic clinical interviews based on dsm - iv - tr criteria were conducted by a child and adolescent psychiatrist .
working memory training software was designed by khodadady , mashhadi and amani ( 1388 ) ; compatible with its english version made by the cogmed company , this software in a form of a computer game presents different tasks to improve the visual and auditory working memory ( 67 ) .
the wisc - iv is divided into fifteen subtests , ten of which formed a part of the previous wisc iii .
the five new subtests include three core tests : picture concepts , letter - number sequencing , matrix reasoning and two supplemental tests : cancellation and word reasoning .
the wisc - iv generates a full scale iq ( fsiq ) which represents overall cognitive ability .
the four other composite scores are verbal comprehension index ( vci ) , perceptual reasoning index ( pri ) , processing speed index ( psi ) and working memory index ( wmi).some studies were conducted to examine the scale s reliability and validity in iran .
there was a significant correlation between wisc - iv , raven s progressive matrices and wisc  ii ( 68 , 69 ) .
after the diagnosis was made by a child and adolescent psychiatrist , snap - iv rating scale and cbcl test were completed by the mother . in the second phase , the wechsler intelligence scale for children - fourth edition
was implemented in order to homogenize the groups in terms of their iqs and to examine whether the participants had any intelligence incompetency .
the third phase included the random assignment of the participants in the treatment groups and the onset of the treatment .
after conducting the pre - tests , the training program derived from the barkley s model was offered to the parent training group over eight private sessions .
the training issues consisted of the following 10 steps : 
 step 1 : introducing adhd and presenting an overviewstep 2 : understanding parent - child relationshipstep 3 : improving positive attention skillsstep 4 : developing positive attention skills and enhancing child acceptancestep 5 : creating a coupon - based economy at homestep 6 : supplementing response coststep 7 : using timeoutstep 8 : managing children s behaviour in public placesstep 9 : making preparations for restraining school problemsstep 10 : back - up sessions step 1 : introducing adhd and presenting an overview step 2 : understanding parent - child relationship step 3 : improving positive attention skills step 4 : developing positive attention skills and enhancing child acceptance step 5 : creating a coupon - based economy at home step 6 : supplementing response cost step 7 : using timeout step 8 : managing children s behaviour in public places step 9 : making preparations for restraining school problems step 10 : back - up sessions during the last session , snap - iv rating scale and cbcl test were completed again by mothers . in the working memory training group , after performing pre - tests , children were required to take part in individual sessions .
besides , visual and auditory computer - based rewards encouraged the child to sustain his / her effort . at the end of the eighth training session
, the post - tests were performed . in the combined group , after completing the pre - tests , both trainings were concurrently presented for the mother and her child .
post - test was performed in the last session . before testing the research hypotheses ,
the wisc - iv intelligence test was conducted to ensure the homogeneity of the participants regarding their intelligence level .
due to gender differences prevalent in adhd subjects , the frequency in each group favored boys .
in addition , the children of the parent training group had the lowest age average in comparison with their counterparts in the other groups .
the highest frequency within the combined treatment group and working memory treatment group were related to the second grade primary school children ; the highest frequency within the parent training group consisted of first grade primary school participants .
the results of mancova revealed no significant differences among the three groups regarding their verbal comprehension iq , perceptual reasoning , processing time and total score ( wilksl= 0.74 , f= 0.95 , p > 0.05 ) .
this plausibly demonstrates the homogeneity of the groups . in the current study , it was hypothesized that combined treatment in comparison with working memory training method , and parent training treatment per se are more effective in suppressing the adhd symptoms .
the following table shows the descriptive statistics of the three groups including means and p < 0.05 , * * * p < 0.001 standard deviations . table 1 indicates means and standard deviations of the participants scores in combined treatment group , working memory training group and parent training group on snap and cbcl tests .
the dependant variables in this analysis included the scores of attention deficit symptoms , hyperactivity/ impulsivity and the total symptoms of snap test as well as the scores of the inattention symptoms ( experience - based scales ) and adhd clinical symptoms ( dsm - based ) contained in cbcl test .
pre - test scores were regarded as control variables and group represented the independent variable .
the results indicated that the test is significant ( c2 ( 14 ) = 229.38 , p<0.001 ) ; this demonstrates a significant correlation among the dependant variables ( 68 ) .
the result of leven s test of error variance homogeneity was not significant ( p.0.05 ) which suggests that error variance was equal across all the levels of group variable .
there was a significant difference among the groups in symptoms reduction ( wilksl= 0.12 , f48 , 10 (= 9.09 , p<.0.05 ) .
as indicated in table 3 , the three groups displayed significant differences in the following variables : attention deficit symptoms ( f2)8&2)= 17.56 , p < 0.001 , 2=0.56 ) , hyperactivity / impulsivity symptoms ( f2 ) 8 & 2)= 10.48 , p<0.001 , 2=0.43 ) , total symptoms ( f2 ) 8 & 2)= 13.78 , p<0.001 , 2=0.50 ) , attention problems ( experience - based scales ) ( f2 ( 8 & 2)= 10.39 , p<0.001 , 2=0.42 ) , and adhd symptoms based on dsm ( f2 ( 8 & 2)= 5.32 , p<0.05 , 2=0.28 )
. comparative analysis of treatment groups employing multiple comparisons ( lsd ) suggested a significant difference between the combined treatment group and the two other groups in all the variables of snap and cbcl tests .
the results indicated a significant difference between the combined treatment group and parent training group in suppressing the symptoms of attention deficit in snap test ( p<0.05 ) .
a significant difference was also found between the combined treatment group and working memory training group ( p<0.001 ) .
furthermore , a significant difference was found ( p<0.001 ) between the combined treatment group and working memory training group in the decline of total symptoms of snap test .
moreover , a significant difference ( p<0.05 ) was observed between the combined treatment group and working memory training group in deficit ( experience - based scales ) of cbcl test .
the difference in attention problems ( experience - based scales ) was also significant between the combined treatment group and parent treatment group ( p<0.001 ) .
moreover , a significant difference was detected between the combined treatment group and working memory training group ( p<0.01 ) as well as between the combined treatment group and parent training group ( p<0.05 ) in reducing clinical symptoms of adhd ( based on dms ) .
table 1 indicates means and standard deviations of the participants scores in combined treatment group , working memory training group and parent training group on snap and cbcl tests .
the dependant variables in this analysis included the scores of attention deficit symptoms , hyperactivity/ impulsivity and the total symptoms of snap test as well as the scores of the inattention symptoms ( experience - based scales ) and adhd clinical symptoms ( dsm - based ) contained in cbcl test .
pre - test scores were regarded as control variables and group represented the independent variable .
the results indicated that the test is significant ( c2 ( 14 ) = 229.38 , p<0.001 ) ; this demonstrates a significant correlation among the dependant variables ( 68 ) .
the result of leven s test of error variance homogeneity was not significant ( p.0.05 ) which suggests that error variance was equal across all the levels of group variable .
there was a significant difference among the groups in symptoms reduction ( wilksl= 0.12 , f48 , 10 (= 9.09 , p<.0.05 ) .
as indicated in table 3 , the three groups displayed significant differences in the following variables : attention deficit symptoms ( f2)8&2)= 17.56 , p < 0.001 , 2=0.56 ) , hyperactivity / impulsivity symptoms ( f2 ) 8 & 2)= 10.48 , p<0.001 , 2=0.43 ) , total symptoms ( f2 ) 8 & 2)= 13.78 , p<0.001 , 2=0.50 ) , attention problems ( experience - based scales ) ( f2 ( 8 & 2)= 10.39 , p<0.001 , 2=0.42 ) , and adhd symptoms based on dsm ( f2 ( 8 & 2)= 5.32 , p<0.05 , 2=0.28 )
. comparative analysis of treatment groups employing multiple comparisons ( lsd ) suggested a significant difference between the combined treatment group and the two other groups in all the variables of snap and cbcl tests .
the results indicated a significant difference between the combined treatment group and parent training group in suppressing the symptoms of attention deficit in snap test ( p<0.05 ) .
a significant difference was also found between the combined treatment group and working memory training group ( p<0.001 ) .
furthermore , a significant difference was found ( p<0.001 ) between the combined treatment group and working memory training group in the decline of total symptoms of snap test .
moreover , a significant difference ( p<0.05 ) was observed between the combined treatment group and working memory training group in deficit ( experience - based scales ) of cbcl test . the difference in attention problems ( experience - based scales ) was also significant between the combined treatment group and parent treatment group ( p<0.001 ) .
moreover , a significant difference was detected between the combined treatment group and working memory training group ( p<0.01 ) as well as between the combined treatment group and parent training group ( p<0.05 ) in reducing clinical symptoms of adhd ( based on dms ) .
various treatment methods for adhd have been presented so far , among which working memory training as a psychosocial method has received substantial support ( 42 , 46 , 47 , 51 , 53 ) .
plethora of research provides evidence that parent training as an evidence - based method is a well established treatment for children with adhd ( 9 ) .
although , research strongly supports the effectiveness of the combination of adhd interventions ( 2 , 9 , 56 , 57 - 59 ) , the effectiveness of the combined methods of working memory training and parental training has not been investigated so far .
therefore , the objective of the present study was to examine the effectiveness of barkley s parent training program , working memory training and the combination of these two interventions for children with adhd .
the results of the present study demonstrated that combined treatment in comparison with the other two methods suppressed the clinical symptoms of adhd more significantly .
hence , it can be concluded that the finding of the present study are consistent with that of other national and international studies , and we recommend combined method as an effective treatment for individuals with adhd ( 56 - 59 ) .
it is worth mentioning that the most significant reductions of hyperactivity / impulsivity symptoms , after combined treatment group , were observed in the group of parent training .
this finding , in particular , indicates the positive impact of changes in parents coping strategies with children s hyperactivity / impulsivity symptoms .
this confirms the finding of previous research that supports parent training approaches in reducing adhd symptoms of children ( 3 , 9 , 25 - 29 ) .
in addition , the present research revealed that after the combined treatment group , the second most significant reduction of children s attention deficit symptoms occurred in working memory training group .
previous researches highlighted the effectiveness of working memory training and regarded this method superior to other psychosocial treatments ( 42 , 46 , 48 - 50 , 52 , 53 ) .
the findings of this study , congruent with previous researches , indicate that parent training program is more effective in reducing the hyperactivity / impulsivity symptoms ( 2 ) and working memory training has a better effect on inattention symptoms of adhd ( 46 ) .
therefore , it seems safe to claim that combined treatment of working memory training and parental training has the best effectiveness on reducing both hyperactivity / impulsivity and inattention symptoms .
a combination of working memory training and parent training as a new approach within the domain of combined treatment methods of adhd tends to not only impact the processes , functioning , and interactions between parents and children but also directly influences the children s memory functioning as one of the key modules of adhd .
substantial research provides evidence for the effectiveness of combined interventions in helping children with adhd ( 9 , 55 , 59 ) .
moreover , combined method can be taken into account as a treatment approach in reducing symptoms and improving deficiencies associated with adhd .
thus , further researches are required to encompass a larger sample of children with adhd to differentiate various treatment methods in terms of their effectiveness and based on the sub - types of the disorder and they should also involve long - term follow ups .
 objectivethe aim of the current study was to examine the effectiveness of barkley s parent training program , working memory training and the combination of these two interventions for children with attention deficit hyperactivity disorder ( adhd).methodsin this study , 36 participants with adhd ( aged 6 to 12 years ) were selected by convenience sampling . 
 revision of the swanson , nolan and pelham ( snap ) questionnaire ( snap  iv ) , child behavior checklist ( cbcl ) and clinical interviews were employed to diagnose adhd . 
 wechsler intelligence scale for children - fourth edition was also implemented . 
 the participants were randomly assigned to the three intervention groups of barkley s parent training program , working memory training and the combined group . 
 snap - iv and cbcl were used as pre - tests and post - tests across all three groups . 
 data were analyzed using mancova ( spss version18).resultsthere was a significant difference ( p < 0.05 ) in the decline of attention deficit and hyperactivity /impulsivity symptoms between the combined treatment group and working memory training group and also between the combined treatment group and the parent training group in snap . in terms of attention problems ( experience - based subscales ) of cbcl , there was a significant difference ( p < 0.001 ) between the combined treatment group and working memory training group . 
 furthermore , compared to the working memory training and parent training groups , the combined group demonstrated a significant decline ( p < 0.01 ) in clinical symptoms of adhd ( based on dsm).conclusionit was revealed that combined treatment in comparison with the other two methods suppressed the clinical symptoms of adhd more significantly . 
Material and Methods
Participants
Instruments
Child Behavior Checklist (CBCL)
Clinical Interviews
Working Memory Training Software
Wechsler Intelligence Scale Fourth Edition (WISC-IV)
Procedure
Results
None
None
None
Discussion
Limitations