IntroductionCommon mental disorders include depression, anxiety and somatoform disorders are a public health problem in developed as well as developing countries. It represents a psychiatric morbidity with significant prevalence, affecting all stages of life and cause suffering to the individuals, their family and communities. Despite this fact, little information about the prevalence of common mental illness is available from low and middle-income countries including Ethiopia. The aim of this study was to determine the magnitude of common mental disorders and its associated factors among adult residents of Harari Region.MethodsComparative cross-sectional, quantitative community-based survey was conducted From February 1, 2016 to March 30, 2016 in Harari Regional State using multi-stage sampling technique. A total of 968 residents was selected using two stage sampling technique. Of this 901 were participated in the study. Validated and Pretested Self reported questionnaire (SQR_20) was used to determine the maginitude of common mental disorders. Data was entered and analyzed using Epi-info version 3.5.1 and SPSS-17 for windows statistical packages. Univirate, Bi-variate and multivariate logistic regression analysis with 95% CI was employed in order to infer associations.ResultsThe prevalence of common mental illnesses among adults in our study area was 14.9%. The most common neurotic symptoms in this study were often head ache (23.2%), sleep badly (16%) and poor appetite (13.8%). Substance use like Khat chewing (48.2%), tobacco use (38.2%) and alcohol use (10.5%) was highly prevalent health problem among study participant. In multivariate logistic regression analysis, respondents age between 25-34 years, 35-44 years, 45-54 years and above 55years were 6.4 times (AOR 6.377; 95% CI: 2.280-17.835), 5.9 times (AOR 5.900; 95% CI: 2.243-14.859), 5.6 times (AOR 5.648; 95% CI: 2.200-14.50) and 4.1 times (AOR 4.110; 95% CI: 1.363-12.393) more likely having common mental illnesses than those age between 15-24 years, respectively. The occurrence of common mental illness was twice (AOR: 2.162; 95% CI 1.254-3.728) higher among respondents earn less than the average monthly income than those earn more than average monthly income. The odds of developing common mental illnesses were 6.6 times (AOR 6.653; 95% CI: 1.640-6.992) higher among adults with medically confirmed physical disability than those without physical disability. Similarly, adults who chewed Khat were 2.3 times (AOR 2.305; 95% CI: 1.484-3.579) more likely having common mental illnesses than those who did not chew Khat. Adults with emotional stress were twice (AOR 2.063; 95% CI: 1.176-3.619) higher chance to have common mental illnesses than adults without emotional stress.ConclusionThis study had reveals that common mental disorders are major public health problems. Advancing age, low average family monthly income, Khat chewing and emotional stress were independent predictors of common mental illnesses. Whereas sex, place of residence, educational status, marital ...