The findings of this study indicate that the prevalence of 24.8% of preparatory students in Addis Ababa were abuse substances. This high prevalence was remained slightly higher as compared with 20.2% prevalence of substance abused obtained from national findings . But it is much lower than a study conducted by students from public Midwestern University (48.1%) .
The investigation of this study showed that the commonly abused substances were alcohol 30.8%, kchat 15.4%, and 11% cigarette. 3.5% of students abuse Cannabis, heroin, and hashish and 2.1% of respondents were abuse sleeping pills. As compared with the prevalence, reports from Kenyan secondary school showed that alcohol 42.9% khat 20.8% cigarette 19.8% cannabis 14.3% and sleeping pills 3.8% were the most commonly abused substances and this study also support and indicated that alcohol was the most commonly abused substance than others, which was similar to this finding .
The prevalence of alcohol, kchat and cigarette abuse was higher than other substances due to cultural, social and legal acceptability. Among the social substance, alcohol does not affect health when moderately consumed. It is also widely available, easily accessible (especially home remedies), high exposure to alcohol advertising and has market coverage. These are the reasons why alcohol is the most commonly abused substance, unlike other substances.
According to this study, Male students were more likely to abuse substances than female students. This is also similar to the study conducted in Mekelle university students . Students who started to use substances through the influence of peer pressure were positively associated with abuse of substances. This is similar to a study conducted in Kenyan secondary school  and Mekelle University students; peer pressure into initiation factors for substance use was positively associated with substance abuse . One of the psychosocial factors which were strongly associated with substance abuse is the curiosity of the students to explore new experiences.
Various studies highlight that the role of curiosity also has a strong positive association with the initiation and continuation of substance abuse among Hungarian secondary high school students . Similarly, respondents in this who started to use substances due to poor family relationships were positively associated with substance abuse. This is in agreement with studies conducted and investigated by Paul  more importantly; young people with a poor relationship with their parents are likely to abuse substances than those who have healthy relationships . Stress found to have a strong association with substance abuse among schools where this study was conducted. The findings of this study reveal the prevalence of ever users of substances among students was found to be 73.4%, 70% and 42.8% in Radical, Lazarist and Menelik respectively. This is lower than findings from Mekelle University students (82.7%) and students in Nigerian medical university (78%) (Igwe, 2009). And higher than Nigerian secondary school students, 63.3% .
The prevalence of substances among ever users of students were, 35% Lazarist 29.4% Radical and 20.8% Menelik had taken only one drug that is alcohol, whereas 10%, 7.6%, and 2.9% were used two substances from Lazarist, Menelik, and radical preparatory schools respectively in their lifetime. And the percentage of ever use of three substances among students was 11.8% in Radical, 5% in Menelik and 3.8% in Lazarist. There were also poly-drug users in Menelik 3.4% and Radical 2.9% but not in Lazarist. In contrast with findings reported from Mekelle University Among the ever users of substances, were 58.1% of students consumed only one drug whereas 42% were poly-drug users.
Substance abuse was significantly high among students of the private preparatory school compared to that of government school students in Addis Ababa. The difference in the educational program in Addis Ababa could be contributing factors to this varying rate of substance consumption.
Other findings in this survey were the time of initiation for substance use was reported to be 57% of the ever users began at secondary school. This is different from reports taken from students of Debre Markos Poly Technique College 36% during their secondary school life. The reason for this should be the different participants' study area, Addis Ababa and that what has been reported from the Debre Markos.
The survey further showed that 42.8% of the study participants were introduced and initiated to use substances by peers or friends. 29.2%, 17.9%, and 10.1% were by curiosity, poor family relationship and stress respectively. As I have already indicated that peer pressure was the prominent psychosocial factor reason for the initiation and continuation of substance abuse among students in private and government preparatory schools. These factors occur sequentially but independently of each other. This result is much lower than 75.1% of students introduced to use substances by peers in Nigeria secondary school. Similar to this, a study conducted in Kenya secondary school stated that peer pressure is the prominent reason for substance abuse.
The present study revealed that students whose friends were substance users or abusers had more likely to use a substance in their life (72.1%). Similarly, studies conducted by Pedersen & Skrondal found that students who have friends’ use of substances had more likely to use substances than those who did not .
Participants who had a strong desire (curiosity) to try substances were more likely to use substances than those who do not and 83.9% of participants were answered agree and 81.8% strongly agreed. In agreement with other findings, 75.8% of the respondents said they first tried illegal substances were due to curiosity . The difference is due to the method difference between the present study and the referred one.
Respondents whose mother and or father dead, divorced and separated had a higher prevalence of substance use 64.9%, 50%, and 48.3% respectively than those who did not. Similar reports also found by Yip et al  and support that students those who had very poor parent’s marital relationship, bad relationship with parents, would have a higher prevalence of drug use.
Other findings from this study also that symptoms or feelings of stress likely to use substances than those who had no feeling of stress. This result also supported by Kaplow et al and he noted that the number of symptoms related to stress at baseline predicted who would start/initiate and continue to use the substance .
In general, the difference showed in the above discussion may be due to the population size difference in the study, and the differences in school policies and advertisement of publicity. The difference in the educational system in private and government schools between countries could also be contributing factors for this varying rate of use and abuse of substances. Institutional property variables of schools, physical and behavioral property variables of schools, including the type of residence, institution size, location, and schools community property variables, including availability and outlet density could also be reasons for the variations.