THE OTTAWA PRENATAL PROSPECTIVE-STUDY (OPPS) - METHODOLOGICAL ISSUES AND FINDINGS - ITS EASY TO THROW THE BABY OUT WITH THE BATH WATER

In the OPPS we have been studying the effects of marihuana used during pregnancy since 1978. The subjects are primarily middle-class, low ri sk women who entered the study early in their pregnancy. Extensive dem ographic and life-style information was gathered several times during pregnancy and postnatally. The offspring have been assessed repeatedly during the neonatal period, at least annually until the age of 6 and less frequently thereafter. The outcome measures include a variety of age appropriate standardized global measures as well as a large batter y of neuropsychological tests attempting to assess discrete functionin g within particular domains including language development, memory, vi sual/perceptual functioning, components of reading and sustained atten tion. The results suggest that in the neonate, state alterations and a ltered visual responsiveness may be associated with in utero exposure to marihuana. Global measures, particularly between the ages of 1 and 3 years, did not reveal an association with prenatal marihuana exposur e. However, this initial, apparent absence of effect during early chil dhood should not be interpreted as in utero marihuana exposure having only transient effects for, as the children became older, aspects of n europsychological functioning did discriminate between marihuana and c ontrol children. Domains associated with prenatal marihuana exposure a t four years of age and older included increased behavioral problems a nd decreased performance on visual perceptual tasks, language comprehe nsion, sustained attention and memory. The nature and the timing of th e appearance of these deficits is congruent with the notion of prenata l marihuana exposure affecting 'executive functioning' - goal directed behavior that includes planning, organized search, and impulse contro l. Such an interpretation would be consistent with the extant literatu re with animals and non-pregnant adult users suggesting that chronic m arihuana use may impact upon prefrontal lobe functioning.