In a cohort of urban African Americans and Puerto Ricans, high levels of self-control at age 14 were associated with low levels of both marijuana use and depressive mood up to age 29. The findings suggest that bolstering ethnic and racial minority children's and early adolescents' self-control might shield them from the burdens of drug use and depression during adolescence and young adulthood.
Dr. Kerstin Pahl and colleagues at the New York University (NYU) School of Medicine extended previous research showing that, in white populations, low self-control heightens the risks for substance abuse and depressive mood, taken singly. The new study is the first to replicate those results in an ethnic/racial minority population and the first to examine how self-control affects the likelihood that a young person will develop both marijuana use and depression.
In 1990, when the Harlem Longitudinal Development Study began, the NYU team assessed the self-control of students from 11 schools in East Harlem, New York. The students, average age 14 years, told the researchers whether they agreed or disagreed that a set of eight statements, which characterize poor self-control, applied to themselves, including:
- “You feel like losing your temper at people.”
- “You’ll do anything on a dare.”
- “When rules get in the way, you ignore them.”
The researchers also asked the students how much marijuana they used and whether they felt unhappy, sad or depressed, and hopeless about the future. The researchers re-interviewed the participants about their drug use and mood every 5 years until they were 29 years of age.
Altogether, 838 participants completed at least 3 of the 4 interviews. About one-quarter of them consistently reported that they never or seldom used marijuana and experienced minimal or no depressive mood. However, nearly 1 in 7 followed a trajectory characterized by both increasing marijuana use and high levels of depressive mood, over the 15 years of study (see Figure). The remaining 60 percent of participants reported mixed trajectories of minimal or increasing marijuana use with low or intermediate depressive mood.
The participants’ levels of self-control in early adolescence strongly predicted which trajectory group they belonged to. Those whose responses at age 14 indicated high levels of self-control were significantly more likely to consistently report slight or no use of marijuana and minimal depressive mood than adolescents in any other trajectory group. They were more than 4 times more likely to be in this relatively problem-free group than to be in the group that had experienced increasing marijuana use and high levels of depressive mood over time.
Text Description of Graphic
Importance of Ethnic/Racial Identity
“When this study began,” says Dr. Pahl, “most of what we knew about human development from childhood into adulthood in general, and about substance use in particular, was based only on samples of white Americans. This motivated us to include ethnic and racial minority youth in the United States into the body of research, to get a more comprehensive picture of this development.”
Dr. Pahl stresses that the findings in this study cannot be used to draw general conclusions about the role of self-control in marijuana use and depressive mood in adolescents nationwide. However, by studying this particular urban population, her team has been able to assess another important factor: How a group’s ethnic or racial identity changes over time, and how that identity influences substance abuse and other psychosocial phenomena.
Dr. Pahl notes, “We’ve found in our previous research with this group that high levels of ethnic identity seem to have a protective effect against substance use and depressive mood.”
The reasons individuals differ in levels of self-control are multi-determined. Genetic predispositions—expressed, for example, in temperament—likely play a role in the development of self-control, but so do parental childrearing practices, a person’s socioeconomic status, cultural background, and potential exposure to traumatic and stressful life experiences, Dr. Pahl says.
Maturity is an important factor: In the East Harlem study, depressive mood became less prevalent in each of the 4 groups by the time participants reached the age of 29. Dr. Pahl and colleagues speculate that this decrease over time may reflect increasing levels of self-control that come with age.
The malleable nature of self-control suggests that interventions can shift it in a positive direction. “The good news is that self-control can be improved over time, and that early interventions can make a difference,” says Dr. Pahl.
Studies have reported that people can gain greater self-control through cognitive-behavioral therapy and mindfulness techniques. These techniques enable individuals to identify the triggers of unwanted behaviors so that they can regulate their emotions and make rational, healthy choices.
Emerging evidence suggests that activities, such as martial arts, yoga, or playing a musical instrument, may also have positive effects on self-control, Dr. Pahl says. “They seem to exercise the executive functions, associated with the prefrontal cortex of the brain, which regulate cognitive processes, including attention, working memory, and impulse control,” she explains.
The researchers conclude that early interventions along with improved understanding of the early causes of low self-control may help reduce adolescents’ vulnerability to drug use and depression.
This study was supported by NIH grants DA000244 and DA005702.
Pahl, K.; Brook, J.S.; Lee, J.Y. Adolescent self-control predicts joint trajectories of marijuana use and depressive mood into young adulthood among urban African Americans and Puerto Ricans. Journal of Behavioral Medicine. 37(4):675-682, 2014. Abstract