This post looks at the correlation between the prevalence of cigarettes, marijuana, and alcohol on a student’s grades. More specifically, the Substance Abuse and Mental Health Data Archive (SAMHDA) asked youth respondents, “How many of the students in your grade at school would you say use cigarettes?” They then repeat this question, substituting cigarettes for marijuana and alcohol.

The results are mostly intuitive. Looking first at the correlation between grades and how many students use cigarettes, Figure 1 shows that 81.31% of students who report they know no one who smokes cigarettes received an A or B average in grades. Only 18.69% received a C or D average in grades.

In contrast, of those who reported that every one they knew smoked cigarettes, only 49.36% received an A or B average in grades. 50.64% of those who reported that every one they knew smoked received a C or D average. This figure shows that those youths who say everyone they know smokes are 2.71 times as likely to receive a C or D average, compared with those who report no one they know smokes.

Next, Figure 2 shows the correlation between grades and the prevalence of marijuana. Students were asked how many students they knew who used marijuana. The correlation, again, is intuitive. Of those who said that no one they knew used marijuana, 80.24% received an A or B average grade. Only 19.76% received a C or D grade average.

In contrast, of those who reported that everyone they knew used marijuana, only 50.43% received an A or B average. 49.57% received a C or D average grade. Again, those who reported that everyone they knew used marijuana were 2.51 times as likely to receive a C or D average grade than those who reported no one they knew used marijuana.

On the topic of alcohol, students were asked how many students they knew who drank alcohol. Of those who reported no one they knew drank alcohol, 79.68% received an A or B average grade. Only 20.32% received a C or D grade average.

On the flip side, those students who reported that everyone they knew drank alcohol, 62.31% received an A or B average grade. 37.69% received a C or D average. Those who reported that everyone they knew drank alcohol were 1.5 times as likely to received a C or D grade average that those who reported that no one they knew drank alcohol. The percentages tell us that the impact of alcohol on receiving a poor grade average is not as pronounced as in the case of cigarettes and marijuana.

Finally, I look at the impact of getting drunk weekly on grade averages. Students were asked how many students they knew who got drunk weekly. For those who reported that no one they knew got drunk weekly, 79.05% received an A or B average grade. 20.95% received a C or D average grade.

On the other hand, those who reported that every one they knew got drunk weekly, 56.64% received an A or B average. 43.36% received a C or D average. Therefore, those who reported that every one they knew got drunk weekly were 2.07 times as likely to receive a low grade average–C or D–as those who reported that no one they knew got drunk weekly.

The results show that grades and the prevalence of cigarettes, marijuana, and alcohol are correlated. In fact, the prevalence of cigarette use seems to have the greatest impact on receiving a bad grade average. The negative impact on grades correlated with the prevalence of cigarette use is followed by the prevalence of marijuana use, getting drunk weekly, and general alcohol use.

Source: https://rdas.samhsa.gov/#/survey/NSDUH-2006-2013-RD08YR?column=YESTSDNK&results_received=true&row=YELSTGRD&run_chisq=false&weight=DASWT_3