Brain Development: Normal Processes and the Effects of Alcohol ...

124 ETHANOL-AFFECTE D DEVELOPMENT
FIGURE 8- 1 Rang e o f effects o f prenatal alcohol exposure o n th e centra l ner -
vous system.
behavior hav e becom e salient . Fo r instance , socia l
and adaptiv e function s hav e bee n identifie d a s im -
paired i n individual s with FA S (Kell y e t al. , 2001) ,
and patient s fro m clinica l sample s ar e reporte d t o
have a hig h frequenc y o f lega l an d menta l healt h
problems (Streissgut h et al, 1996 ; Fam y et al, 1998 ,
Fast an d Conroy , 2004) . Thes e issue s are discusse d
below, in addition to recent researc h o n neurodevel -
opmental outcomes in affected individuals.
METHODOLOGICAL CONSIDERATIONS
Despite 3 0 year s o f study , ther e remai n significan t
disagreements i n the literatur e and among th e pub -
lic and man y professionals about the effect s o f prenatal
alcohol exposure . Some of these discrepancies can
be accounte d fo r b y difference s i n methodologie s
used to study this phenomenon. Before undertaking a
review of the researc h literatur e i n thi s area, i t is important
t o understan d ho w methodolog y affect s out -
comes an d t o acknowledg e tha t thes e issue s are no t
specific to this field.
It i s obviousl y impossible , ethicall y an d practi -
cally, to carry out tru e experimental studie s of the effects
o f prenatal alcohol exposur e on human growth ,
behavior, and cognition. For those aspects of development
tha t cannot b e modele d i n animal studies , research
mus t b e don e i n eithe r clinica l sample s o f
already affected individual s or i n cohort s of offsprin g
of wome n wh o drin k durin g pregnancy . Eithe r ap -
proach ha s rea l value and rea l difficulties . A s experimental
contro l o f the "independent " variable i s no t
possible, suc h studie s mus t b e correlationa l an d de -
scriptive. In addition, it is usually not possible to con -
trol completely the confounders or effect modifier s in
such situations . When conductin g studie s with sam -
ples o f individual s drawn fro m clinica l settings , re -
searchers mus t tak e int o accoun t systemati c biase s
and confounders . Childre n diagnose d wit h FA S or
other effect s o f prenatal alcohol exposur e come to the
attention o f professionals because o f problems i n be -
havior or development. Thus, it is inappropriate to use
such sample s to evaluate the relationshi p between alcohol
exposure and these particular outcomes. Nevertheless,
stud y o f suc h childre n ma y b e valuabl e fo r
other research purposes . Also, many clinically identified
alcohol-affecte d childre n hav e negativ e earl y
caregiving histories resulting from materna l substanc e
abuse, out-of-hom e placement , and othe r caregiving
failures, and researc h wit h suc h group s must include
similar contrast group s to avoid confusing the effect s
of pre- and postnata l environment s on the outcome s
of interest.
In addition to being very expensive and time con -
suming, exposur e samples also have methodological
limitations. Wome n wh o drin k durin g pregnancy
usually also smoke tobacco and ma y use other drugs
(Day e t al , 1993 ) (se e Chapte r 19) , introducin g
other confounders into the research. They may have