Interpretation of imaging findings may also be clouded by the ages of the children in the samples. Normal developmental changes in brain maturation could be confused with effects of prenatal drug exposure when children are studied in a cross-sectional manner across a wide age range, especially when the age ranges span periods of major changes in brain development such as early childhood and adolescence. Among the alcohol studies, for example, the ages of the children ranged from 8-22145, 18-37152 and 3-13 years161. Among the tobacco studies the children were 12-18 years. This means that some of the children in these cohorts will be using substances themselves. Thus, the effects of prenatal drug exposure on the brain development may be confounded with effects of current substance abuse.
