this is a cross - sectional study based on the primary health care clinics of qatar . the survey was conducted among qatari nationals between 25 and 65 years of age during a period from january to july 2007 . a multistage stratified sampling design was developed using the administrative divisions of the primary health centres in qatar that had approximately equal numbers of inhabitants . the sample size was determined on a priori presumption that the prevalence rate of somatisation in qatar would be more or less similar to rates found for several other countries in the arabian gulf and eastern mediterranean ( 13 , 15 ) , where the reported prevalence of somatisation among adults ranged from 15% to 20% . assuming the prevalence of somatisation to be 17% , with the 99% confidence interval for an error of 2% at the level of significance , a sample size of 2,320 would be required to meet the specific objectives of the study . of the total 22 primary health care clinics available , this study was approved by research and ethical committee of hamad medical corporation , qatar . during the study period , a consecutive series of 2,320 patients were selected from the register of the recruited health centres . only patients attending the primary health care centres for scheduled routine follow - up appointments or new complaints were approached . of the approached 2,320 patients , 1,689 responded to the 12-item general health questionnaire ( ghq-12 ) with a response rate of 72.8% . the research assistants conducted a face - to - face interview with the patients and completed questionnaires until they reached the required sample size . also , patients who were not willing to disclose their personal information and medical history were not included in this study ( 631 patients ) . a consultant and training held two sessions for administering the ghq-12 , the socio - demographic questionnaire , cis and the procedure as a whole . after dealing with the presenting complaint , the individuals were considered to be probable cases for clinical interview on the bases of scores above the cut - off point on ghq-12 items . a sample of 404 out of 1,689 ( 23.9% ) scored more than 13 in ghq were planned for the clinical interview schedule ( cis ) using cis questionnaire . identified cases were assigned diagnoses according to the icd-10 classification of mental illness ( 16 ) . the severity of their illness was measured according to the total weighted score ( tws ) scores . ( 17 ) as a self - administered questionnaire that would identify non - psychotic psychiatric cases . the ghq-12 is the shortest version of the ghq and it is concerned mainly with psychoemotional disturbance . the arabic version of the ghq-12 has already proven to be a valid instrument for screening psychiatry morbidity among arab primary health care patients in qatar ( 1 ) . it consists of questions designed to elicit the presence or absence of 10 defined psychiatric symptoms and 12 manifest abnormalities ( 17 ) . each item of psychiatric symptoms and manifest abnormality was graded on 5 points ( 04 ) , 0 = absent , 1 = mild , 2 = moderate , 3 = severe , 4 = very severe ) . the tws is calculated by adding the sum of the 10  reported symptoms scores plus twice the sum of the 12  manifest abnormality scores . for the purpose of this study the criteria used to define a psychiatric case was a tws of 20 or more . this threshold was found appropriate when previously used in uae ( 13 , 18 , 19 ) . to avoid ambiguity and overgeneralisation in using the term somatisation in this sample , we adopted the restrictive operational criteria set by bridges and goldberg ( 20 ) and el rufaie et al . the bridges and goldberg criteria for somatisation include two terms which are subject to rating bias . first is the decision required of the interviewer as to whether the physical symptoms can be explained by the psychiatric disorder , and second is the interviewer 's opinion on whether these symptoms could be alleviated by suitable treatment . the classification of the pgs and sts is as follows : sts : patients with psychiatric disorder who presented to their gp with physical complaints , but in whom a functional diagnosis was recorded.pgs : patients with psychiatric disorder who presented to their gp with psychological complaints.among the 404 psychiatric cases identified , 210 patients were classified as sts and 194 patients were pgs according to bridges and goldberg 's operational criteria ( 20 ) . sts : patients with psychiatric disorder who presented to their gp with physical complaints , but in whom a functional diagnosis was recorded . student 's t - test was used to ascertain the significance of differences between mean values of two continuous variables and confirmed by non - parametric mann multivariate stepwise linear regression analysis was performed to determine the predictors of sts and pgs . ( 17 ) as a self - administered questionnaire that would identify non - psychotic psychiatric cases . the ghq-12 is the shortest version of the ghq and it is concerned mainly with psychoemotional disturbance . the arabic version of the ghq-12 has already proven to be a valid instrument for screening psychiatry morbidity among arab primary health care patients in qatar ( 1 ) . it consists of questions designed to elicit the presence or absence of 10 defined psychiatric symptoms and 12 manifest abnormalities ( 17 ) . each item of psychiatric symptoms and manifest abnormality was graded on 5 points ( 04 ) , 0 = absent , 1 = mild , 2 = moderate , 3 = severe , 4 = very severe ) . the tws is calculated by adding the sum of the 10  reported symptoms scores plus twice the sum of the 12  manifest abnormality scores . for the purpose of this study the criteria used to define a psychiatric case was a tws of 20 or more . this threshold was found appropriate when previously used in uae ( 13 , 18 , 19 ) . to avoid ambiguity and overgeneralisation in using the term somatisation in this sample , we adopted the restrictive operational criteria set by bridges and goldberg ( 20 ) and el rufaie et al . the bridges and goldberg criteria for somatisation include two terms which are subject to rating bias . first is the decision required of the interviewer as to whether the physical symptoms can be explained by the psychiatric disorder , and second is the interviewer 's opinion on whether these symptoms could be alleviated by suitable treatment . the classification of the pgs and sts is as follows : sts : patients with psychiatric disorder who presented to their gp with physical complaints , but in whom a functional diagnosis was recorded.pgs : patients with psychiatric disorder who presented to their gp with psychological complaints.among the 404 psychiatric cases identified , 210 patients were classified as sts and 194 patients were pgs according to bridges and goldberg 's operational criteria ( 20 ) . sts : patients with psychiatric disorder who presented to their gp with physical complaints , but in whom a functional diagnosis was recorded . student 's t - test was used to ascertain the significance of differences between mean values of two continuous variables and confirmed by non - parametric mann multivariate stepwise linear regression analysis was performed to determine the predictors of sts and pgs . from the total of 1,689 patients studied , 404 were identified for cis ( 23.9% ) . the socio - demographic characteristics of sts and pgs are shown in table 1 . among the 404 identified psychiatric cases , 210 patients were sts ( 52% ) and 194 were pgs ( 48% ) , a ratio of 1.1:1 . the prevalence of somatisation was 12.4% of the total studied sample , while for psychologisation it was 11.5% . somatisation and psycholgisation were significantly more frequent among the middle - aged patients , especially in the age group of 3039 years ( 40.5% vs. 44.3% ; p=0.01 ) . somatisation was higher in female patients ( 51.4% ) , whereas psychologisation was more frequent in male patients ( 56.2% ) . there were no significant differences observed in their gender , marital status , education and occupation . the socio - demographic characteristics of somatisers and psychologisers a total of 1,689 patients were the study patients who responded to the 12-item general health questionnaire ( ghq ) . the severity of psychiatric illness as measured by the tws of the patients suffering from different types of disorders is given in table 2 . the severity of the psychiatric illness ; generalised anxiety disorder , depressive episode , recurrent depressive disorder , dysthymia , prolonged depressive reaction were significantly more in pgs ( p<0.001 ) . the severity of psychiatric illness in both somatisers and psychologisers note : ns , not significant ; tws , total weighted score . results of the comparison of postulated determinants in both sts and pgs are shown in table 3 . family history of psychiatric disorder ( p=0.014 ) and physical illness during adulthood were higher in pgs than sts . significant physical illness during adulthood before the onset of presenting symptoms was significantly higher in pgs ( 23.2% ; p=0.007 ) . dissatisfaction at work was significantly higher in sts ( 63.8% ; p=0.007 ) , while dissatisfaction with social life was significantly higher in pgs ( 77.8% ; p=0.007 ) . results of the comparison of postulated determinants in both somatisers and psychologisers chi - square test was performed . the factors associated with sts and pgs using multivariate stepwise linear regression analysis is listed in table 4 . most episodes of depression and anxiety  the common mental disorders  are contained and managed in primary care . common somatic symptoms are the main reason for the primary health care visits ; they are also concomitants of anxiety and depression ( 14 ) . many patients with psychological disorders present to their gp with common somatic symptoms this combination has been referred to as  somtisation and is associated with lower rates of diagnosis of depression and anxiety . most studies in other countries have looked at patients ' beliefs about their symptoms that have focused on the dichotomy between somatising and psychologising . in the arab region , very few studies have been conducted on somatisation and this study is the first attempt to document the differences between sts and pgs in primary care qatari patients . a who cross - cultural study reported the prevalence of somatisation ( 19.7% ) with a range of 937% in 15 primary care centres ( 21 ) . the prevalence rate of somatisation in qatar ( 12.4% ) was lower than the international prevalence of somatisation ( 19.7% ) , but similar to the proportion of uae ( 12% ) ( 19 ) . in saudi arabia ( 22 ) , psychiatric morbidity in primary care is estimated at 3046% with a 19.3% prevalence of somatisation and 20% of depression which is higher than the prevalence found in qatar . also , the present study revealed a higher prevalence of somatisation ( 12.4% ) than psychologisation ( 11.5% ) . our results are comparable to uae , but inconsistent with the study in saudi arabia which demonstrated a higher prevalence of psychologisation than somatisation . our prevalence rates are comparable in relation to somatisation , but not to psychologisation which is consistent with another study that over half of their patients with diagnostic illness were sts , whereas only about one - fifth were pgs ( 14 ) . ratio of sts : pgs in the present study was 1.1:1 which is similar to the ratio reported in a study on somatised mental disorders among primary care arab patients conducted in uae ( 13 ) ( 1.1:1 ) . but the results of the spanish study revealed that somatic patients were three times more prevalent than pgs in primary care ( 21 ) . among the identified psychiatric cases in the present study , 52% of them were sts and 48% of them were pgs . our ratio is consistent with reports in non - western cultures claiming higher somatisation rates . in conformity with other reports , there was no significant difference between the sts and pgs groups in relation to gender , educational level and marital status ( 2224 ) . but , a study ( 5 ) reported that the group of sts had a significantly lower level of education and tended to be older ( p=0.05 ) which is consistent with the results of the study ( 14 ) that st would have lower level of education and would belong to a lower social class . the reason for this finding is that patients who have received less education may be less able to elaborate and interpret their psychological distress . in the present study , the diagnostic categories , mixed anxiety and depressive disorder and prolonged depressive reaction , were common in both pgs and sts in the current study . however , prevalence of generalised anxiety disorder , recurrent depressive disorder , dysthymia , depressive episode and brief depressive reaction were more prevalent among the pgs than the sts . the uae study also reported that the severity of most psychiatric illness was estimated to be greater among the pg group than the sts ( 19 ) . it is important that primary care physicians acquire specific skills for the recognition of depression . our study revealed that stressful life events was significantly more among sts than pgs which was comparable to the findings of another study ( 23 ) . for sts , general health and adverse childhood experience were strong positive predictors , whereas for pgs general health and impairing life or social life were positive predictors . the erroneous diagnosis of depression in patients leads to the risk of unnecessary and potentially dangerous medication . in conclusion , the present study revealed that the prevalence of somatised mental disorder was little higher than the psychologised mental disorder . the prevalence of somatisation and psychologisation is comparable with other reported studies from the middle - east and western countries . dissatisfaction at work and stressful life events within the 12 months before the onset of the presenting symptoms were significantly more among sts than pgs . for sts , general health and adverse childhood experience were strong predictors for sts , whereas general health and impairing family or social life were significant predictors for pgs . it is important to have educational programmes that raise awareness of the full spectrum of somatic symptoms as well as aiming to improve attitudes and consulting skills in primary care . the authors have not received any funding or benefits from industry to conduct this study .