Our study showed that 57% of pharmacy and medical students of Zabol University of Medical Sciences who participated in the study had at least one episode of self-medication during the past six months. The prevalence of self-medication in Iran and other countries highly varies among different demographic groups. For example, a similar study among medical and pharmacy students in Ethiopia reported a prevalence of 38.5% . Also, 44.8% of Bahraini , 78.6% of Indian , and 55.2% of Egyptian  medical students reported episodes of self-medication. In another study, 98% of Palestinian students  reported self-treatment. Among studies in European countries, two studies performed on Slovenian  and Serbian  students reported frequencies of 92.3% and 79.9%, respectively. A study on a Spanish adult population also reported 45% prevalence for self-treatment for cold . A study on German adolescents showed a self-medication prevalence of 8% . In another study on patients with gastro-esophageal reflux disease in France, self-medication was reported by 17% of the participants . Overall, the results of the present study showed a much higher prevalence of self-treatment compared with developed countries and similar to that of developing countries. It has been shown that the prevalence of self-medication is generally higher in developing than developed countries . This difference could be due to differences in the levels of welfare and income per capita and therefore the ability to pay for health cares, the quality of health care services, as well as the efficiency of monitoring programs on prescription of drugs by supply centers .
Among the studies conducted in other parts of Iran, self-medication was reported in 91% of Kerman students , 83% of Yazd University of Medical Sciences students , and 80% of Ardabil students . A review study conducted in 2015 by Azami et al. reported frequencies of 53% and 67% for self-medication in Iranian general population and students, respectively  which were close to the prevalence reported in the present study. Self-medication seems to be typically higher among students than the general population. This could be due to a variety of reasons such as students' higher pharmaceutical and clinical knowledge, their better access to the Internet and mass media advertising pharmaceutical products, and the cost-effectiveness and time-saving nature of self-medication . Nevertheless, populations under the study, and research and data analysis methods are different in various studies making difficult to compare the prevalence of self-medication among different societies.
The results of the present study showed that there was no significant difference in the frequency of self-medication between the medicine and pharmacy students. The presence or absence of chronic diseases also had no significant impact on the rate of self-treatment among the students. However, male students had more frequently used self-medication than females. This observation was different from that of two other studies in which females have self-medicated more commonly than males [22, 23]. In a number of studies; however, there were no significant differences between males and females in this regard [21, 25].
Regarding the knowledge, only 12.9% of our students were able to correctly name three OTC drugs. The ratio of students who could recall 2 or more OTC drugs was 39.4%, and the rest of the students knew either one or none of the OTC drugs. In a study on pharmacy students in Addis Ababa, Ethiopia, 47.3% of students did not know the OTC drugs as well. In the next part of the knowledge survey, the participants' knowledge was assessed using the Isacson's and Bingforse method . Overall, 26.5% of the students had poor scores, while 43.5% and 30% attained average and good scores respectively. In line, a similar study on Palestinian students using the same grading method reported that one-third of students had poor scores while others acquired average and good scores . In general, medical and pharmaceutical students seem to need more effective educations in this area.
According to our results, students with higher drug information were more likely to self-medicate. In a review study, Isacson et al. showed an association between drug knowledge and a positive attitude toward self-medication  which was consistent with our observation. Gender had no significant impact on drug information, but the field of study significantly overshadowed the students’ drug information. Pharmacy students had higher levels of pharmacological information than medical students. Overall, 16% and 35% of our medical and pharmacy students achieved good scores regarding drug information. This indicates the difference in the number of drug courses between the two groups and deeper integration of pharmacy students with pharmaceutical products. Also, senior students (two-year and higher) had superior levels of drug information than juniors (one-year) indicating the impact of educational courses on their drug knowledge.
In the attitude section, each student was given an attitude score based on the answers provided to multiple statements. A higher score indicated a more negative attitude towards self-treatment. The only variable that had a significant impact on attitude score was the field of study as pharmacy students had more negative attitude than medical students which may be related to their higher pharmaceutical knowledge. A study by James et al. in 2005 also noted that higher levels of medical and pharmaceutical knowledge make people more cautious about taking and recommending medications .
Regarding the students' performance, cough and cold along with headache were the most common self-treated ailments. These results were consistent with those of most similar studies [23, 37, 38]. Antibiotics (74.4%) and painkillers (60%) were the most commonly drugs used for self-medication among our students. In a study on first-year medical students in Bahrain, only 6% of participants used antibiotics for self-treatment . In other studies, this rate reached 17.2% in Ethiopia , 38.9% in Serbia , 19.9% in Palestine , and 34% in India . These rates of antibiotic usage for self-treatment are much lower than those of European and developed countries . In a study by Aljinovicet al. in Croatia, they found that using antibiotics for self-treatment was higher among people working in healthcare systems than the general population  supporting our observation in this study. The rate of self-administrated antibiotic use observed here was similar to most other studies conducted in Iran and higher than rates reported in other parts of the world. According to this, the risk of antibiotic resistance may be a serious threat to our society in future.
The most important reason for self-medication was noted as the non-acute nature of the disease, and the most common information sources were previous prescriptions among our students. These observations were consistent with previous reports in this field . Our participants reported their academic knowledge (40%) and confidence in the knowledge (31%) as the most common information source and cause of self-medication, respectively. This evidence may reflect the fact that our students were aware of the dangers of self-medication; but at the same time, they believed that they were equipped with sufficient knowledge to stay safe. Nevertheless, our results showed that only 16% of medical students and 35% of pharmacy students had good drug information levels. An important point in our study was the students’ low tendency to consult with a pharmacist as one of the most accessible sources of ensuring safe self-treatment. Only 13.7% of the students mentioned consulting with a pharmacist as one of their information sources for self-treatment. Medical students seem to need more education about the dangers of irresponsible self-treatment.