drug abuse or dependence is derived from a set of factors including social and family issues , availability , and individual s disposition ( 1 , 2 ) . personality is another factor that may play an important role in preparation , acceleration , or maintenance of drug abuse or dependence behaviors . personality disorders are highly observed among drug abusers both in clinical population ( 3 , 4 ) and non - clinical population ( 5 - 7 ) . moreover , personality is a significant clinical feature that also affects smoking patterns and may influence the nicotine withdrawal syndrome expressions ( 8) . the influential role of a number of personality traits in drug abuse and dependence is proved . transferring from regular smoking stage to dependence stage numerous studies recognized that in addition to personality traits , onset age of smoking is also one of the important predictor variables in future dependence to other illegal substances . many studies concluded that smoking is a risk factor among teenagers to be addicted to other drugs . kandel et al . reported a significant relation between smoking cigarettes and use of other illegal drugs among high school students ; the use of illegal drugs in smokers who smoked daily was much higher than non - smokers ( 10 ) . findings of several studies indicate that 98% of hashish users , before starting to use hashish , had used to smoke tobacco , and onset age of using hashish in these individuals was lower than the starting age of hashish consumption ( 11 ) . individual traits such as genetic preparedness and personality traits , or environmental factors such as drug availability or peer influence , and lower age of smoking onset are among the strong predicting factors in future dependence that can explain the sequence of starting from one drug to another ( 12 ) . the current research aimed to investigate the personality traits and onset age of smoking cigarettes as predicting variables in future use of illegal drugs . the present research was a causal - comparative study performed on 45 male nicotine addicts and 45 male opiate dependent individuals . using random sampling , the researchers attended a smoking cession center in qazvin , iran , and then , individuals who had been recognized to be nicotine dependent , according to the fagstrome questionnaire and diagnosis of the physician in that center , were selected . these individuals had passed six months of their treatments in this center and did not display smoking withdrawal symptoms . the inclusion criteria were lack of severe psychiatric disorders and non - dependence on different types of drugs . additionally , the researchers randomly attended four treatment centers for drug abuse and dependence in qazvin and individuals recognized to be drug dependents , according to the maudsley addiction profile and physicians diagnosis , were selected . these individuals had passed six months of their treatments and they did not display any drug withdrawal symptoms . the inclusion criteria were smoking , lack of severe psychiatric disorders and non - dependence on different types of drugs . moreover , the onset age of smoking cigarettes in these individuals was recorded . at the beginning of the sampling process , in both groups , individuals who were qualified to participate in the groups data were analyzed by spss software version 16 , using anova and multivariate regression tests . temperament includes novelty seeking , harm avoidance , reward dependence , and persistence ; and character dimension includes self - directedness , cooperativeness , and self - transcendence . the internal reliability of the revised version , translated by ayati , chemikar , and pourshahbaz is 0.82 ( 14 ) . this 60-item questionnaire was applied to find the therapeutic results including four areas : 1 ) drug use , 2 ) physical health , 3 ) mental health , and 4 ) high - risk behaviors . the internal correlation coefficient of this questionnaire is higher than 0.75 and its reliability is reported 0.65 - 0.74 ( 15 ) . temperament includes novelty seeking , harm avoidance , reward dependence , and persistence ; and character dimension includes self - directedness , cooperativeness , and self - transcendence . the internal reliability of the revised version , translated by ayati , chemikar , and pourshahbaz is 0.82 ( 14 ) . this 60-item questionnaire was applied to find the therapeutic results including four areas : 1 ) drug use , 2 ) physical health , 3 ) mental health , and 4 ) high - risk behaviors . the internal correlation coefficient of this questionnaire is higher than 0.75 and its reliability is reported 0.65 - 0.74 ( 15 ) . both groups were homogeneous in terms of their variables . in the education variable , a significant inter - group difference was observed . table 2 indicates the statistics related to the comparison of seven personality dimensions between the two groups . as indicated , there was a significant difference between the two groups . it means that novelty seeking in dependents of opiate drugs was higher than those of dependents of nicotine ( p = 0.000 ) . cooperativeness of opiate addicts was lower than that of nicotine addicts ( p = 0.000 ) . the obtained results indicated that the mean of smoking onset in dependents of opiate drugs was lower than that of the dependents of nicotine . table 3 demonstrates the t - test results for the variable of onset age of smoking . the obtained results indicated the significance of logistic regression in variables of onset age of smoking cigarettes , education , and personality traits in predicting the dependence on opiate substances ( table 4 ) . according to table 4 , low onset age of smoking cigarettes , lower education level , along with lower scores in self - directedness and cooperativeness traits , predict future dependence on opiate substances . the obtained results indicated a significance difference between the two groups in the dimensions of novelty seeking and cooperativeness . novelty seeking reflected a hereditary orientation in onset or activation of novelty seeking response , approach to reward cues , active avoidance of conditioned punishment cues , and unconditioned punishment escape . this dimension is observed as an exploratory activity in responding to novelty , impulsivity , exaggeration in approaching to reward cues , indulgence and disorder , fatigue and quick fed up , and active avoidance of failure . behavioral responses sent after novelty seeking includes exploratory pursuit , voracity , active avoidance , and escape . therefore , opiate addicts have traits such as indulgence in approach to reward cues , impulsivity , novelty seeking and pursuit of reward cues that distinguish them from the other groups . many of these traits cause an individual to go towards activities in which the person looks for reward cues , seeks novelty , and acts impulsively . also , novelty seeking dimension in drug addicts was higher than that of the ordinary population , and in some studies , it was higher than that of the alcohol addicts ( 16 , 17 ) . thus , findings of the current research can be explained as follows : opiate dependent individuals have traits such as indulgence in approach to reward cues , impulsivity , novelty seeking , and pursuit of reward cues that distinguishes them from the other groups . drug , itself , is a very strong incentive reward and affects the reward system of the brain . drug dependent individuals use drugs to supply the dopamine for their limbic system which is the reward system of brain , ( 18 ) . also , these people display behaviors such as exploratory pursuits of drugs , active avoidance of withdrawal cues ( including pain , and unpleasant physical and mental states ) and voracity . voracity is one of the important factors in drug abuse , staying in withdrawal , and failure to return . voracity is high in drug addicts and high voracity has a negative correlation with successful withdrawal . this dimension of personality traits in the current research was compatible with many of the previous studies in this area such as results gained by ball et al . ( 22 ) . also , cooperativeness dimension in opiate dependent inpatients was significantly lower than those of the other groups . individuals with higher degrees of this dimension consider themselves as an inseparable member of the human society and are , generally , sympathetic , patient , compassionate , merciful , and supportive , and adhere to the principles and rules . people with low cooperativeness are self - attracted , impatient and intolerant , critical , avenger , and opportunistic . these individuals do not usually assist others , and in every situation , first think about themselves . also , they intend to be inattentive about other people s emotions and rights . these people are intolerant , do not adhere to the principles and rules , and are inattentive to others emotions and rights . the difference of nicotine addicts and ordinary population with opiate dependent individuals in this dimension relates to supportiveness , adherence to the rules and principles , participation in group works , compassion , kindness , and patience . this finding is in agreement with the findings of many previous studies such as those of evren et al . evren et al . ( 21 ) argued that high novelty seeking is one of the distinguished features in category b of personality disorders , namely , the same category in which anti - social personality disorder is placed ; therefore , drug dependent individuals with higher novelty seeking may have symptoms of anti - social personality disorder . le bon et al . ( 8) found that heroin abusers ( an opiate substance ) personality profile indicate more anti - social personality traits compared to that of alcohol addicts . evren et al . ( 21 ) also pointed out that reward dependence is one of the characteristics of category a , high reward novelty seeking is one of the characteristics of category b , and high harm avoidance is one of the characteristics related to category c of personality disorders ( 21 ) . moreover , results showed that low onset age of smoking cigarettes , lower education , and low cooperativeness and self - directedness dimensions predicted future use of opiate drugs after onset of smoking cigarettes . in a research performed on the onset age of drug use , chen et al . ( 23 ) identified that low onset age of smoking is one of the predisposing factors for future drug use . this implies that the lower the onset age of smoking , the more probable that the person refers to using other illegal drugs ( 23 ) . ( 12 ) reported that the average onset age of smoking in their research samples was 13.4 ( 13.3 for boys , 13.5 for girls ) , and the mean ( average ) onset age of using alcohol was 15.1 ( 15.0 for boys , 15.2 for girls ) . it implies the lower age mean in smokers . experiencing tobacco before starting to use hashish occurred in 98% of hashish users ( 12 ) . guxens et al . ( 11 ) indicated that tobacco and alcohol use preceded the use of hashish and the performed meta - analyses showed that it is 1.7 to 2.6 times more likely that tobacco and alcohol consumers use hashish . therefore , the current research results are in accordance with those of other studies , indicating that lower onset age of smoking is a predisposing factor for future use of other drugs . also , it is natural that when self - directedness traits are cases such as responsibility , purposefulness , trouble - shooting , self - acceptance , and adapting to society s norms , then this dimension can play an effective role to predict drug dependence . self - directedness is , to some extent , a component of a coherent ego that enables individuals to delay satisfying their needs , be self - accepted , purposeful , and responsible . low cooperativeness dimension in the present research is another predicting factor of drug dependence . as mentioned in the previous sections , cases such as empathy , sympathy , usefulness , and having a clean heart therefore , cooperativeness can be another component of a coherent ego , it means that individuals can consider norms of the society , be socially useful , and have empathy and a clean heart . in general , three dimensions of self - directedness , cooperativeness , and self - transcendence can , to some extent , reflect an individual s coherent ego and degree of sophistication . then , it can be explained that low character dimensions in opiate addicts , that were low in all three dimensions in this research , can indicate ego incoherence and non - sophistication . 21 ) in their research concluded that high novelty seeking and low cooperativeness along with low onset age of smoking cigarettes predict drug dependence . in their study , subscales predicting drug dependence were more reasonable than low age , lower scores in subscales of sympathy and compassion vs. malice and usefulness , and higher scores in subscale of spiritual acceptance vs. materialism . therefore , low self - directedness and cooperativeness , low onset age of smoking cigarettes and low education can predict drug dependence . according to the current and prior studies , it is clarified that many of the people using illegal substances have some personality characteristics such as novelty seeking , and antisocial traits that cause to start smoking in lower ages , and then approach to use any kind of substances .