Most of the subjects (89.2%) lack any psychiatric disorder. The prevalence of subjects with no lifetime DSM-III-R diagnosis in a study in Oslo was 47.7% [9
]. Also, the rate in the National Co-morbidity Study in the USA was 52% [10
]. Although the two study samples were taken from the general population, they used the Composite International Diagnostic Interview [11
] and DSM-III-R criteria. This difference may be based on the instrument and method used in their studies. For example, the Norway study focused on the population of Oslo, a large city with different social problems when compared to small cities or villages. This generalization cannot be applied to the whole country. It is possible that some depressive and anxiety disorders are more common in larger cities with a higher rate of disorder. The National Co-morbidity Survey in the United States [9
] was a large cross-sectional population study with a design that was not comparable to our study. Also, the US study was limited to respondents aged 15–54. Plus, they used a paper and pencil version. These differences in the psychiatric interview may be responsible for the differences in the findings.
A cross national study showed that one third of the subjects experienced at least one disorder at some time in their life in Brazil (36.3%), Canada (37.5%), Germany (38.4%), Netherlands (40.9%), and the USA (48.6%). Lifetime prevalence estimates were considerably lower in Mexico (20.2%) and Turkey (12.2%) [12
]. The current study shows that psychiatric disorders are not infrequent in Iran. As many as 10.81% of the subjects reported having experienced one or more psychiatric disorder at some time in their lives. However, it is lower than the rate reported in the study that used GHQ-28 [4
]. The difference may be due to the method and tool used for screening and diagnosis of the disorders. The SADS included 16 groups of psychiatric disorders whereas the GHQ-28 questionnaire only studies the symptoms of anxiety, depression, somatisization and social dysfunctions.
The present study shows that the rate of psychiatric disorders in women is higher than men (14.34% versus 7.34%) which are consistent to the results of some studies conducted in Iran and other countries [4
]. However, a study in Netherlands, reported that more than four out of ten respondents (41.2%) reported a lifetime prevalence of at least one DSM-III-R disorder. The most common psychiatric disorders were major depression, alcohol abuse and phobias with no significant difference between men and women (42.5% versus 39.9%). More than 15% of the respondents had major depression in their history. Though they did not find gender differences in the overall prevalence of mental disorders, differences did emerge when the disorders were examined separately. Obsessive-compulsive disorder was the only exception among the anxiety disorders [15
] that was more prevalent among men. In the current study, all types of the psychiatric disorders were more common in females than males except BMD, acute brief psychotic disorder, somatoform disorder, and amnestic disorder.
In a study in Brazil based on ICD-10, it showed that nearly 46% of the sample had at least one lifetime mental disorder, i.e., almost one in two respondents reported a given disorder at some time in their lives [5
]. They reported that women were more likely than men to have mood disorders (with the exception of bipolar disorder, for which there were no gender differences), and anxiety disorders (except for obsessive-compulsive disorder, social phobia, and generalized anxiety disorder). There were no gender differences in the rates of somatoform disorders.
The results of the some previous studies showed a different pattern, with the highest prevalence typically occurring among the youngest age groups [[12
], and [17
]]. The current study shows that the prevalence of psychiatric disorders in the ages of 41 and over is more than the age group 18–40. A study in Norway showed that the most common age group was 30–39 [9
]. The rate in the USA was more in the age group 25–34 [10
The highest estimated prevalence was found among respondents at the lowest level of educational attainment. This is in accordance with results of six of the seven surveys of the cross national study (Canada, USA, Brazil, Mexico, Germany, Netherlands, and Turkey). Germany was the exception (with an insignificant relationship) [12
]. Also, it was consistence with the study in Norway [9
Some studies have found an occupational gradient in the prevalence of common psychiatric disorders [18
]; others have failed to find such association [19
]. Our result is similar to the later study. A study in Brazil using ICD-I0 classification showed that except for anxiety disorders, unemployed respondents were more likely to have any lifetime disorder. Students, homemakers, and retired persons were all less likely to have any psychiatric morbidity [5
] when compared with the employed.
The rates of most types of psychiatric disorders in urban areas are higher, when compared to rural areas. These findings are reinforced by the previous study [3
]. Recently, a study showed that the difference was not statistically meaningful [20
]. It is possible that other factors that are related to location of residence are more important, such as: poverty, unemployment, lower socioeconomic status, and sex.
The differences in the methods of selecting the samples, operational definition of variables, data gathering methods, and tools are considered as important factors in inconsistencies with the results. In particular, the validity and reliability of the tool should be considered. The validity and reliability of SADS was well reflected in the previous studies [21
]. However, the validity and reliability of western societies does not confirm its validity in countries with deep cultural difference. The effects of cultural factors on estimating the prevalence of psychiatric disorders through diagnostic interviews has been shown in previous studies [23
]. The present study shows that the prevalence rate of bipolar mood disorder (BMD) was 0.96%, the results of the other studies showed a different pattern. Findings reported by the recent multi-center European study prevalence rate of BMD reveal even lower frequencies under 1%. Data from surveys of large samples showed the lifetime prevalence rates of BMD around 1.5%. A main question is whether the low prevalence rates of BMD are not an artifact of the over diagnosis of depression [24