Background Mental disorders are always remained a neglected public health problems in low and middle-income countries (LMICs), most people with mental disorders never receive effective care and there is a large treatment gap. In order to solve the problem integration of mental health into primary health care is recommended and in Ethiopia implementation of the scale of mental health services at primary health care level was started in 2014. For the success of the integration of mental health into primary health care, primary care health professionals are the key personnel who are responsible for the management of mental, neurologic and substance use disorders. However, proper training and education of primary care health professionals is mandatory for an optimal performance and success of integration. This interventional study was conducted to assess the effectiveness of mental health training course for scale up of mental health services at primary health care level in Ethiopia. Methods This quasi-experimental pre- and post-study design was conducted in Ethiopia from October to December 2016 using quantitative data collection methods. A total of 94 primary health care professionals were included in the study. The intervention was conducted by psychiatry professionals using standardized World Health Organization (WHO) Mental Health Gap Action Programme (mhGAP) guide prepared for scaling up of mental health care through integration into primary health care (PHC) and general medical services. Pre- and post intervention assessment was done for knowledge, attitude and practice (KAP); and statistically analyzed. A paired sample t test with p values was performed to test the differences between the pre- and post-test. In additions mean and standard deviation of the responses were calculated. Overall the response rate was 100% at the end of the intervention. Results The study resulted in a significant improvement in knowledge, attitude and practice (KAP) of PHC workers about all the four mental, neurologic and substance use disorders during the post intervention survey (p < 0.05). Post intervention the knowledge of health professionals increased by 53.19% for psychosis, 42.56% for depression, 19.25% for epilepsy and 54.22% for alcohol use disorders. Similarly, post intervention attitude increased by 55.32% for psychosis, 40.42% for depression, 36.17% for epilepsy and 43.6% for alcohol use disorders. In addition, post intervention case identification rate increased by 62.78% for psychosis, 55.46% for depression, 21.35% for epilepsy and 41.49% for alcohol use disorders with significant p value (p < 0.05). Conclusions The study results suggest that mental health training could be an effective intervention for improving knowledge, attitudes, and practices among primary health care professionals regarding mental, neurologic and substance use disorders. Training is a prerequisite and vital to enhance the knowledge, attitude, and practice of primary care professionals which plays a significant role for the easy success of integrated care and treatment of mental, neurologic and substance use disorders into the existing general health care services.
