Thus far, to the best of our knowledge, this is the first study that determined the epidemiology of misdiagnosis as well as detection rates of severe psychiatric disorders including schizophrenia, schizoaffective, bipolar, and depressive disorders in a specialized psychiatric setting. The results of our evaluation revealed that a remarkable proportion of people with severe psychiatric disorders were misdiagnosed and the detection rates of the distinct categories of severe psychiatric disorders were relatively low. This study shows that roughly three out of four and one out of two patients with schizoaffective and major depressive disorders respectively were misdiagnosed. We also found that roughly one in four and one in five of patients with schizophrenia and bipolar disorder respectively were misdiagnosed. In addition, the current study demonstrated remarkably low detection rates of schizoaffective disorder (25%), depressive disorder (42.40%), bipolar disorder (72.22%) as well as schizophrenia (76.29%). Having a diagnosis of schizoaffective and depressive disorders as well as suicidal ideation were found to be significant predictors of misdiagnosis.
The possible reasons for the misdiagnosis
There are so many explanations for the observed considerable level of misdiagnosis of severe psychiatric disorders. First, failure to appreciate the significance of extensive and expert psychiatric history is among the important factors for the misdiagnosis. In support of this view, evidences indicated that psychiatric history taking is the most important component in the evaluation and care of patients with mental disorder [35, 36]. Additionally, psychiatric history taking is considered as a part of the treatment process (first stage of treatment process) where we collect important information for final psychiatric diagnosis. So, it is strongly recommended that adequate time must be given in taking a history from the patients with average length time roughly up to 45 minutes but the length of time varies depending on the setting, the complexity of the presentation, the purpose of the interview and other factors (including additional assessment tools for the quality or other purposes of services) [10, 35, 36]. However, according to the unpublished study report that assessed the length of time for psychiatric assessment in the same setting in Ethiopia found that the average length of time for psychiatric evaluation was only five minutes. Secondly, the severity and complexity of the presentation might be the other reasons for the misdiagnosis. This is because as the study was conducted in a tertiary hospital, the patients were more likely to serve and referred from the different areas of the country, and the more severe the disorder the more likely to be the overlapping presentation leading to misdiagnosis [37, 38]. In support of the above explanation, the current study found that a remarkably higher proportion of people with bipolar (88.89%) and depressive (69.56%) disorders had overlapping psychotic symptoms and nearly one in five of patients with schizophrenia had depressive symptoms during evaluation. Thirdly, the higher rates of misdiagnosis could be attributed to the low level of clinical experience, knowledge about the psychiatric disorders and diagnostic criteria’s, as well as the subjective nature of the diagnosis due to the absence of any supporting laboratory evidence in diagnosis of psychiatric disorders [5, 39, 40]. This is because in Ethiopia professionals without psychiatry specialty as well as diploma and degree level trained psychiatry nurses were involved in care, diagnosis, and treatment of patients with mental disorders because of the scarcity of specialized manpower . Finally, the diagnostic instability and the change from one disorder to the other disorder over time might be the other possible attributing factor for the misdiagnosis. Because in the current study the average duration of the disorder was 10 years and epidemiologic evidence indicates that as many as 50% of patients with bipolar disorder had a shift to non-bipolar disorder at least once over ten years .
Comparing with the existing literature
In the present study, the commonly misdiagnosed disorder was found to be schizoaffective disorders (75%) followed by major depressive disorder (54.72%), schizophrenia (23.71%), and bipolar disorder (17.78%). Of those patients who were missed by the professionals and diagnosed as a schizoaffective disorder by SCID criteria by assessors, most frequent of them were received schizophrenia diagnosis 15 (53.57%) in the chart. The remaining diagnosed as bipolar 5 (17.86%) and depressive 1 (3.57%) disorders in the medical record. The possible reason for higher misdiagnoses of schizoaffective disorder could be the clinical presentation and the required criteria to diagnose schizoaffective disorders are more complex containing similar symptoms to schizophrenia and mood disorder episodes (manic or depressive episodes) . Additionally, the criteria to diagnose schizoaffective disorder are more strict requiring the presence of psychotic symptoms occurring for at least two weeks without prominent mood episodes . Our findings are supported by previous epidemiology study that found the least interrater reliability and low diagnostic congruence for schizoaffective disorders as compared with schizophrenia, bipolar, and major depressive disorders .
The findings of the current study indicating bipolar disorder as the least misdiagnosed disorders as compared to the other severe psychiatric disorders are supported by the validation study that identified bipolar disorder as the disorder with the highest degree in both diagnostic congruence and interrater reliability as compared with schizophrenia, schizoaffective, and depressive disorders . However, the rate of bipolar disorder misdiagnosis was remarkably lower than the results of the previous studies conducted in chine 76.8% . The possible reasons for this difference might be due to the variations in the episodes, presenting symptoms as well as the difference in the characteristics the professionals used to evaluate the disorders.
The current study also demonstrated that bipolar disorder patients are more likely to be diagnosed as schizophrenia (60%) whereas schizophrenia was most likely diagnosed as bipolar disorder (56.25%). The possible reasons might be due to the severity of the bipolar disorder in the current study where 88.89% of bipolar disorders had psychotic features. Supporting this view a study found that the presence of psychotic symptoms in bipolar patients was associated with misdiagnosis  and the majority of patients with bipolar with psychotic features were misdiagnosed as psychotic disorders including schizophrenia [46, 47]. These findings are different from the previous scientific evidence which resulted in depression (70.6%) as the most likely missed diagnosed disorder instead of bipolar disorders . The other possible reason for the difference is that in the present study nearly half of bipolar patients had only manic episode in their lifetime which more resembles schizophrenic symptoms than depressive symptoms.
We also found that depressive disorder was most likely diagnosed as schizophrenia (54.72%). The possible reasons for this might be the presence of psychotic symptoms (66.67%) in addition to the depressive symptoms in patients with major depressive disorders detected by SCID criteria.
Moreover, having a diagnosis of schizoaffective [AOR=12.39 (95%CI 4.50-34.16)], and depressive disorders [AOD=4.22 (95%CI 1.69-10.56)], as well as suicidal ideation [AOR=2.19 (95%CI1 1.24-3.87)] were found to be significant predictors of misdiagnosis. These findings were in agreement with similar previous studies [21, 27].
Consistent with previous epidemiologic studies , this study revealed that the detection rates were highest for schizophrenia, followed by bipolar, depressive, and schizoaffective disorders.
Implications for future research and clinical practice
The current study had some implications for future research as well as clinical practice. First, this study shows that the misdiagnosis and poor detection rates were remarkably higher in patients with severe psychiatric disorders especially for schizoaffective and depressive disorders which need future robust longitudinal research confirming the magnitude and evaluating the possible reasons for the highest magnitude. Second, in the current studies, we included specific categories of mental disorders by distributing the overall sample size calculated for severe psychiatric disorders. This shows that the sample for each disorder may below the estimate the magnitude for distinct categories of the disorders. So future studies addressing this issue are warranted. Thirdly, attention needs to be given to possibly reduce the extensive level of misdiagnoses by the concerned body with the possibilities of implementing continues medical education (CME) so that the patients will be safe from suffering related to persistence symptoms as well as unnecessary and inappropriate drug uses leading to an increased level of severity of the disorders due to misdiagnosis and side effects of drugs.
Strengths and limitations
This study had several strengths: (1) being the first study to estimate and compare the level of misdiagnosis and detection rates across the severe psychiatric disorders such as schizophrenia, schizoaffective, bipolar, and depressive disorders. (2) the use of standard and diagnostic instruments (SCID) to examine severe psychiatric disorders. (3) inclusion of the participants from a well-defined catchment area and assessing the indicators of severity such as psychosis in bipolar and depressive disorders which are the possible reasons for a remarkably high magnitude of misdiagnosis.
However, the current study had also some limitations: first, due to the cross-sectional nature of the study factors associated with misdiagnosis may not imply causality. Second, the possibilities of recall bias due to the retrospective nature of the might impact the magnitude of misdiagnosis.