The aim of this study was to investigate the factors affecting AAS use among bodybuilders in Hamadan using PWM.The importance of the method in the present study is the use of random forest data mining model to investigate the effect of different factors on AAS use. One of the important features of the random forest model is the determination of the functional form of the relationship between the predictors and the response through the data itself. In other words, the functional form of the relationship between different factors and AAS use is not selected by the analyst, but the data determine this functional form. Therefore, this model is able to take into account the complex relationships between different factors with response and provide more accurate predictions. But based on our search in different databases, so far no study has been performed in which PWM and random forest model have been used to predict the factors affecting AAS use.
According to the results of the univariate analysis (Table 1), history of sport club, alcohol use, use by coaches ,use by the best athlete friend and nutritional supplement use in AAS users were more likely than other subject, so this difference was statistically significant (P-value < 0.05). However, the two groups did not differ significantly in terms of demographic variables such as age, degree of education and marital status (P-value > 0.05). In this study, 27.1% of bodybuilders reported a history of anabolic steroid use, which is consistent with a similar study (26). However, the rate of steroid use in the present study is higher than 4.3% that reported by Ghobain et al (27) and it was less than 64% that was result from the study by Bijeh et al. (28).This discrepancy can be due to differences in the target community as well as differences in the geographic areas studied. For example, the target community of Ghobain's study was all Saudi athletes, but if these studies were performed only on professional bodybuilders, the prevalence of anabolic steroid use would increase (29). In general, it seems that the prevalence of anabolic steroids among Iranian bodybuilders is higher than other countries, which shows the importance of paying attention to prevention in this field.
Based on the results, the highest correlation was obtained between behavioral intention with behavioral willingness (r = 0.574) and attitude (r = 0.514). Thus, people with higher behavioral willingness scores also had higher behavioral intention and attitude scores. The results of the random forest analysis confirm the above mentioned result (Fig. 2), behavioral willingness and attitude had the greatest impact on predicting behavioral intention. In the study of Patiro et al., there was a direct relationship between attitude and behavioral intention of AAS use, which is consistent with the results of the present study (30). Also in the study of Abedini et al. attitude, subjective norms and behavioral willingness were reported as predictors of intention to use hookah among students (14).
Analysis of the social reaction path in PWM showed that subjective norms, attitude and positive prototypes about AAS users are associated with willingness to AAS use. This result is consistent with the results of a study in which the attitude and prototypes, were strong predictors for predicting of willingness to doping (31). The results of a similar study showed that attitude, subjective norms and prototypes were factors that predicted willingness to smoking among adolescents in Hamadan city .These factors predicted 43% of willingness variation that in the meantime, the role of subjective norms was more prominent than attitude and prototypes (32). Various studies on substance abuse prevention show that training of life skills such as problem solving and decision making skills increase cognitive-coping skills, which this reduces the tendency of individuals to use a variety of illicit substances. In this regard, other studies have pointed to the training of resistance skills against insistence of peer, such as the skill of saying "no"(33).
The results of the present study showed that reasoned action path is a better predictor for substance use in compare with social reaction path. By comparing the order of importance of intention and willingness in prediction of AAS use, the results showed that behavioral intention is a better predictor for AAS use (Fig. 4). In other words, the decision-making process for anabolic steroids use is based on people's previous intentions. In this regard, various studies have confirmed the effect of behavioral intention on predicting and occurring high-risk behaviors (34–36). However, the results of a study by Barati et al. showed that behavioral willingness in compare with behavioral intention was a better predictor of smoking behavior and these two structures predict a total of 43% of behavior variation (32). In other studies related to the PWM, the behavioral willingness structure has a higher predictive ability in compared with behavioral intention that is not consistent with the findings of the present study (37, 38). Age and previous experiences of individuals, may be explain the inconsistency of the results of the present study with other studies. Usually, as age increase, their life experiences increase, so they make more rational decisions (39). The mean age of the participants in the present study was 25.21 years, while in other studies, participants were mostly adolescents. Evidence suggests that the relationship between intention and behavior in adolescents is weaker than in other individuals (12). On the other hand, some similar studies have described experience as the reason for this problem and have pointed to the weakness of the relationship between intention and behavior in less experienced people (40). As can be seen from the results of random forest (Fig. 4), age is one of the most important factors for predicting AAS use.
One of the limitations of this study was the poor cooperation of some bodybuilders in filling the questionnaire. Also this study was performed only on male bodybuilders, therefore it is suggested that in future studies comprehensive comparison conduct between male and female bodybuilders as well as athletes of other sporting disciplines such as wrestling, weightlifting, and gymnastics.