In the present study, we analyzed data from 12th KYRBS to examine the influence of the parental smoking status on the risk of tobacco, alcohol, and illegal drug use by adolescents. The effects of parental smoking or maternal/paternal smoking as well as of maternal smoking and paternal smoking were analyzed separately. Sex differences in the risk of substance use as a result of parental smoking were also determined. Additionally, the unique effect of parental smoking on substance use by adolescents was determined by analyzing the onset age, current use, as well as amount and frequency of substance use.
The results showed that smoking by both parents constitutes a significant risk factor for substance use by adolescents compared with smoking by one parent or no smoking by both parents. First, the smoking behavior of both parents increased the smoking rate and degree among adolescents. Evidence clearly shows that parental smoking is a risk factor for smoking by adolescents. Loureiro et al. reported that parental smoking increased the smoking rate among both boys and girls , whereas Powell and Chaloupka found that the smoking rate of adolescents increased significantly even when only one parent smoked . Importantly, the results from the present study showed that parental smoking increased smoking risk in children more than maternal/paternal smoking. This suggests that smoking by adolescents is affected not only by the parental smoking status but also by the number of smokers at home.
The identified risk remained significant even when the analysis was adjusted for the effect of second-hand smoking at home. As reported in previous studies, parental attitudes and educational policies toward smoking have a marked impact on adolescent smoking, indicating that parental smoking serves as a role model for adolescent smoking [3, 13, 14]. Okuda et al. showed that adolescents whose both parents smoke show a stronger tendency to smoke and a greater difficulty to quit than those whose only one or no parent smokes . Therefore, parental smoking is more dangerous than maternal/paternal smoking because it increases second-hand exposure to smoking at home, thus allowing children to develop a positive attitude toward smoking.
In the present study, we found that parental smoking affected children of both sexes differently and that the sex of the smoking parent constitutes a different risk factor for the smoking behavior of children. Parental smoking constitutes a significant risk factor for the smoking rate among girls and for the degree of smoking among boys. Maternal smoking produced unique results compared with parental smoking or paternal smoking because it affected the smoking rate of boys and girls differently, significantly increasing the rate of current smoking among boys but decreasing it among girls. Interestingly, girls whose mothers smoked had a higher smoking degree than others.
Previous studies have referred to the differential effects of parental smoking according to the sex of the smoking parent and children. In fact, several studies have found that the effects of both parental and peer smoking on adolescents vary with their sex [12, 13, 16] and that the effects of parental smoking vary with the sex of the smoking parent [11, 17]. According to Loureiro et al., parents of the same sex as their children act as a stronger role model for smoking , with smoking fathers increasing the smoking rate among boys and smoking mothers increasing this rate among girls. On the other hand, Resen pointed out that irrespective of the sex of children, maternal smoking constitutes a greater risk factor than paternal smoking . Therefore, the available evidence is not fully consistent, suggesting that the effects of parental smoking on the onset and duration of smoking by adolescents are a result of a complex interplay between the sex of parents and that of children [18, 19]. In addition, previous studies conducted in Korea have shown that the school environment and mental health issues such as depression have a significant impact on smoking by adolescents [20–22]. Therefore, further longitudinal studies are needed to closely observe such causal relationships.
Regarding the use of alcohol, the results showed that parental smoking increased the rate and degree of alcohol drinking by adolescents compared with parental nonsmoking or maternal/paternal smoking even after the adjustment for second-hand smoking at home. Currently, there are only few evidences regarding the relationship between parental smoking and alcohol drinking by adolescents, although it is well known that smoking and alcohol drinking are closely related . Some studies have found evidence on a relationship between parental substance use other than alcohol drinking, such as tobacco use, and alcohol drinking by children [24, 25]. Based on large-scale surveys on Korean adolescents, the present study provides convincing evidence that parental smoking can promote alcohol drinking by adolescents and that parental smoking constitutes a higher risk for smoking by adolescents than maternal/paternal smoking.
We also examined the effects exerted by maternal smoking on substance use other than nicotine use by adolescents. We found that while maternal smoking constitutes a risk factor for alcohol drinking behavior in children, paternal smoking exerts a relatively smaller effect. These results are consistent with those of a study by Capaldi et al., who found that among the parental use of various substances, the most robust predictor of alcohol drinking by adolescents is maternal smoking . We also revealed that maternal smoking markedly increased the use of illegal substances by boys. Previous studies have reported that a favorable attitude of parents toward the use of various substances, including nicotine, constitutes a risk factor for the use of illegal substances by adolescents . Smoking and alcohol drinking or other substance use by mothers can greatly increase the risk of use of illegal drugs, including marijuana, by adolescents [27, 28].
Several potential causes may underlie the negative effects exerted by maternal smoking on substance use by children. First, mothers may have a greater contribution to the attitude of children toward substance use than fathers. Usually, mothers spend more time with their children and tend to develop a more intimate relationship with them than fathers [29, 30]. Consequently, maternal attitudes may have a greater impact on a child’s attitude and value formation . Accordingly, it is assumed that maternal smoking is more likely to lead children to form a permissive attitude toward substance use than paternal smoking.
Second, maternal smoking may lead children to develop antisocial attitudes. Substance use by adolescents is closely related to antisociality . In Asia, including in Korea, smoking by females is considered contrary to social customs because it is considered a masculine trait [33, 34]. Therefore, smoking mothers may serve as antisocial role models within Asian cultures, potentially leading to more antisocial behavior (including due to substance use) by adolescents.
The present study has several limitations. First, it was conducted through an online questionnaire, thus reflecting self-reported smoking behavior only. Because the smoking behavior of adolescents can be masked by various reasons, the reliability of self-reported smoking is relatively limited. Therefore, further studies using an objective evaluation of smoking, such as physiological indicators, are required. Second, there may have been confounding variables that were not accounted for. In the present study, the general characteristics of adolescent smokers whose parents were also smokers were easy to determine based on the panel data. However, other psychosocial factors affecting parent–child relationships, such as adolescents’ perceived parental attitudes toward substance use and parenting characteristics, were difficult to assess. We suggest the construction of a sophisticated model aiming at a more accurate evaluation of these characteristics in subsequent studies. Finally, the present study was based on cross-sectional panel data; therefore, it was difficult to perform a longitudinal observation due to the nature of data. Future studies may provide a causal understanding of the parent–child interaction or sex differences of parent and children on adolescents’ smoking behavior through longitudinal observations.