Table 1.

Comparison of characteristics of 3 important prospective longitudinal studies

CHARACTERISTICOPPS9MHPCD2,10GENERATION R1,11
Year study began197819822001
PopulationCaucasian, primarily middle classLargely African American (57%) and single (71%), with low SESMultiethnic cohort; slightly higher SES compared with nonresponders or incomplete responders
RecruitmentSelf-referral for study participation based on posters in prenatal clinics and information from prenatal providersActively recruited from an inner-city prenatal clinic in the 4th or 5th mo of pregnancyEnrolled based on residence in the study area with a due date during recruitment. Recruited from early pregnancy until birth
Cannabis-exposed population and total sample size, n/N78/698307/763220/7531
Polysubstance useYes: tobacco (21%) and alcohol (76%)Yes: alcohol (65%), tobacco (53%), cocaine (3.6%), and other illicit drugs (8.6%)Yes: alcohol (31%), tobacco (39%), and other substances (4.5%)
Method of data collection to determine cannabis useRepeated interviews largely within each woman’s home by the same trained, female interviewer for each interviewStandardized interviewsSelf-reported questionnaires
Categorization of cannabis exposureNonuser, light user (≤ 1 joints/wk), moderate user (2–5 joints/wk), or heavy user (> 5 joints/wk)Based on ADJ: light (0–0.4 ADJ), moderate (0.5–1 ADJ), or heavy (> 1 ADJ) useNonuse, occasional (monthly), moderate (weekly), or heavy (daily) use
Cannabis use measuredEach trimesterFirst, second, and third trimester, and 8 mo, 18 mo, and 36 mo postpartumPrepregnancy, early pregnancy, and late pregnancy
Retention rateAt 22 y only 49 (63%) of the group exposed to cannabis remainedOf the total sample, 636 (83%) followed up at 10 y, 580 (76%) at 14 y, and 608 (80%) at 22 yFollow-up rates for the total sample at 6 y exceed 80% for most measures
Limitations
  • Small sample with small number of heavy (n = 25) and moderate (n = 37) users

  • Low-risk sample

  • Self-reported use, although used the same interviewer for all interviews in an effort to build rapport

  • Large, high-risk sample with potential for multiple confounding variables

  • Substantial polysubstance use with alcohol, tobacco, cocaine, and other illicit substances

  • Self-reported use of cannabis

  • Likely highest-potency THC products owing to increasing potency over time and increased potency of Dutch cannabis products

  • Self-reported use of cannabis

  • Use of self-report questionnaires skewed the sample to a higher SES and more educated sample compared with nonresponders or incomplete responders

  • ADJ—average daily joints, MHPCD—Maternal Health Practices and Child Development, OPPS—Ottawa Prenatal Prospective Study, SES—socioeconomic status, THC—tetrahydrocannabinol.