Prevalence and incidence of drug use among college students: an 8-year longitudinal analysis

Abstract

Background: Drug use among college students is associated with adverse academic and health outcomes and risks to personal safety.

Objectives: This study utilized data from a longitudinal study to estimate annual prevalence, cumulative lifetime prevalence, and incidence of ten types of drug use during the eight years after college entry and the average age of onset of each drug used.

Methods: Participants (N = 1,253; 52% female) were young adults who were originally enrolled as first-time, first-year students at a university in the mid-Atlantic US. Annual personal interviews gathered data about the use of seven illicit drugs and three prescription drugs used nonmedically. Annual follow-up rates ranged from 76 to 91%.

Results: Marijuana was the most commonly used drug in every year of the study, with the highest annual prevalence estimates in Year 3 (47%_wt). In Year 8, when the modal age of participants was 25, 29%_wt used marijuana during the past year. Nonmedical use of prescription drugs was more prevalent during college than in the later years of the study. Although the prevalence of cocaine and ecstasy use was low (cumulative prevalence estimates of 17%_wt and 13%_wt, respectively), incidence for these drugs was particularly high in the later years of the study.

Conclusion: Drug use is prevalent among college students, and drug use persists among young adults, even after many have graduated college. More attention should be directed at identifying and intervening with students at risk for drug use to mitigate possible academic, health, and safety consequences.

Keywords: College students; drug use; longitudinal studies; nonmedical prescription drug use; substance use.

Figure 1

Annual prevalence of drug use by year among the College Life Study sample (N_wt=3,285). Note. Weighted for sampling and attrition. Data on prescription drugs reflect nonmedical use only. Data on amphetamines and methamphetamines were combined due to low prevalence.

Figure 2

Cumulative lifetime prevalence of drug use, by study year and type of drug (N_wt=3,285). Note. Data labels represent %_wt (SE). Data were statistically weighted to adjust for sampling design and attrition at each wave. Squares denote lifetime prevalence in Year 1 (i.e., first year of college, ages 17 to 20). Circles denote lifetime prevalence in Year 8. Data on prescription drugs reflect nonmedical use only. Data on amphetamines and methamphetamines were combined due to low prevalence.

Figure 3

Cumulative lifetime prevalence of drug use by age 24, by type of drug and age at onset of use (N_wt=3,285). Open circles denote the median age of onset for a given drug. Note. Data labels represent %_wt (SE). Weighted for sampling. Prevalence is estimated based on all 1,253 individuals in the original baseline sample through age 24, which was the maximum age that all participants had attained by Year 8, and therefore is not comparable to the results in Figure 1. Weighted cumulative lifetime prevalence by age 24 is reported in the label for each drug. Drug use onset that occurred at older ages is not shown in this figure because it was not assessed for every participant. Missing data were treated as non-use, and therefore results represent minimum estimates. Data on prescription drugs reflect nonmedical use only. Data on amphetamines and methamphetamines were combined due to low prevalence.

Figure 4

Frequency of drug use during the past year in Years 4 and 8, among users of each drug. Note. Data on prescription drugs reflect nonmedical use only. Data for Inhalant use in Year 8 was not included due to an overall n<20. Data for Amphetamines/Methamphetamine and Heroin are not included due to overall n<5.