This study found:
- Children’s risk of marijuana and alcohol use and attitudes toward marijuana were influenced by their parents’ marijuana use pattern over time.
- Children whose parents used marijuana primarily during adolescence/early adulthood and those whose parents continued to use marijuana from adolescence through adulthood were at highest risk.
When parents use drugs such as marijuana, their children may also be affected. Numerous studies have shown that current parental marijuana use increases the children’s risk of substance use and other psychiatric problems. A recent NIDA-sponsored study demonstrates that the parents’ history of marijuana use throughout their lifetime may also affect their children’s outcomes and that some lifetime use patterns are more harmful than others.
Parents Fall Into Four Lifetime Marijuana Use Patterns
To identify associations between parents’ marijuana use over time and their children’s outcomes, Dr. Marina Epstein and colleagues at the University of Washington and University of Colorado Boulder followed 426 families from 2002 to 2018. During this time, the families—which included one parent, their oldest biological child, and (where available) another caregiver—were interviewed 10 times. The study evaluated information obtained from 380 families who completed interview rounds 5 to 10, when the children were 6 to 21 years old.
In earlier analyses, the researchers classified the participating parents into four categories based on their lifetime marijuana use (see Figure 1):
- Nonusers, who had never, or almost never, used marijuana in their lifetime.
- People with an adolescence-limited pattern, whose marijuana use began in early adolescence, peaked in their late teens/early 20s, and typically stopped by their mid-20s.
- Chronic users, whose marijuana use began in early adolescence, escalated until approximately the mid-20s, and then persisted into their 30s.
- Late-onset marijuana users, who initiated drug use in their late teens/early 20s and maintained infrequent but consistent use into adulthood.
Past Parental Marijuana Use Puts Children at Increased Risk
The research team next investigated how these use patterns related to a variety of child outcomes, including marijuana, alcohol, and cigarette use; attitudes towards marijuana use; internalizing, externalizing, and attention problems; and school grades when the children were 6 to 21 years old. The analyses found that, compared with children of nonusers, children of parents with adolescent-limited or chronic marijuana use were 2.5 to 4.4 times more likely to use marijuana themselves and 1.8 to 2.75 times more likely to use alcohol (see Figure 2). In contrast, children of late-onset marijuana users had no increased risk of marijuana use. Children of chronic marijuana users also were somewhat more likely to use cigarettes, report more favorable views on marijuana, or exhibit externalizing behavior and lower grades.
The increased risk for children of chronic users resulted mainly from the parents’ ongoing marijuana use. For children of parents with adolescent-limited marijuana use, however, the increased risk remained even after the researchers accounted for current parental marijuana use. Additionally, these children expressed significantly more favorable attitudes toward marijuana use. This indicates that parents’ marijuana use during adolescence, regardless of whether it continues into adulthood, can affect the children’s outcomes. “Over and above ever using marijuana, results from this study show that past patterns of use can have ongoing effects on child outcomes, in particular child marijuana use and pro-marijuana norms,” says Dr. Epstein.
With the number of adults who use marijuana rising following the drug’s legalization in several states, the effect of prior and current parental marijuana use on their children is an increasingly significant public health concern. This study suggests that efforts to reduce children’s risk of drug use must take into consideration not only the parent’s ongoing marijuana use but also their use history. “The field needs to become more nuanced in how marijuana use is handled in research and clinical settings,” adds Dr. Epstein.
This research was supported by NIDA grants DA023089, DA012138, DA033956, and DA009679.
- Text Description of Figure 1
The figure shows four curves illustrating parental marijuana use patterns throughout their adolescence and early adulthood. The horizontal x-axis shows the parents’ age on a scale from 14 years to 30 years. The vertical y-axis represents the level of marijuana use from no use, through infrequent use, to frequent use. A green line with triangles that runs parallel to the x-axis represents nonusers who reported no marijuana use at all timepoints assessed. A purple line with circles represents parents with adolescent-limited marijuana use. These parents had low levels of use beginning around age 14, which increased to almost infrequent use by age 18 and then declined again to reach no use by age 24. A blue line with diamonds indicates parents with a chronic marijuana pattern. Marijuana use begins at low levels at age 14, increases steadily to reach a peak about midway between infrequent and frequent use by age 24, and then declines again to infrequent use by age 30. A red line with squares represents parents with a late-onset use pattern. These parents begin to show low levels of marijuana use by age 18, which increases to halfway between no use and infrequent use by age 24, before declining again to almost no use by age 30.
- Text Description of Figure 2
The two graphs show the probability of marijuana use (top) and alcohol use (bottom) of children of parents with different marijuana use patterns throughout their adolescence and young adulthood. Blue curves with diamonds represent children of chronic marijuana users, red curves with squares represent children of late-onset users, green curves with triangles represent children of nonusers, and purple curves with circles represent children of adolescent-limited users.
(Top) The horizontal x-axis shows the children’s age on a scale from 10 years to 21 years and the vertical y-axis shows the probability of marijuana use on a scale of 0 to 1.0. For children of nonusers (green curve) and late-onset users (red curve), the probability of marijuana use was about 0 at ages 10 to 14, about 0.1 at age 16, about 0.2 at age 18, about 0.3 at age 20, and about 0.25 at age 21. For children of adolescent-limited marijuana users (purple curve), the probability of marijuana use was 0 at ages 10 to 12, about 0.05 at age 14, about 0.2 at age 16, about 0.4 at age 18, about 0.5 at age 20, and about 0.4 at age 21. For children of chronic marijuana users (blue curve), the probability of marijuana use was about 0 at ages 10 to 12, about 0.1 at age 14, about 0.3 at age 16, about 0.55 at age 18, about 0.65 at age 20, and about 0.6 at age 21.
(Bottom) The horizontal x-axis shows the children’s age on a scale from 6 years to 21 years and the vertical y-axis shows the probability of alcohol use on a scale of 0 to 1.0. For children of nonusers (green curve), the probability of alcohol use was 0 at ages 6 to 14, about 0.15 at age 16, about 0.25 at age 17, about 0.3 at age 18, about 0.4 at age 20, and about 0.45 at age 21. For children of and late-onset users (red curve) and adolescent-limited marijuana users (purple curve), the probability of alcohol use was 0 at ages 6 to 12, about 0.1 at age 14, about 0.2 at age 16, about 0.45 at age 18, about 0.6 at age 20, and about 0.6 for children of late-onset users and 0.65 for children of adolescent-limited users at age 21. For children of chronic marijuana users (blue curve), the probability of alcohol use was about 0 at ages 6 to 12, about 0.1 at age 14, about 0.3 at age 16, about 0.55 at age 18, about 0.7 at age 20, and about 0.75 at age 21.
- Epstein, M., Bailey, J.A., Furlong, M., et al. An intergenerational investigation of the associations between parental marijuana use trajectories and child functioning. Psychol Addict Behav 2019 Sept 9 [Online ahead of print]