Maternal lifestyle factors in pregnancy risk of attention deficit hyperactivity disorder and associated behaviors: review of the current evidence.

OBJECTIVE: The purpose of this review was to examine the literature assessing the relationship between prenatal exposure to nicotine, alcohol, caffeine, and psychosocial stress during pregnancy to the risk of developing behavioral problems related to attention deficit hyperactivity disorder (ADHD) in childhood.
METHOD: PubMed, MEDLINE, EMBASE, and PsycINFO were searched systematically. Studies using DSM diagnostic criteria and other validated diagnostic or screening instruments for ADHD and those examining ADHD symptoms were included. A narrative approach was used because the studies differed too much in methods and data sources to permit a quantitative meta-analysis.
RESULTS: Twenty-four studies on nicotine (tobacco smoking), nine on alcohol, one on caffeine, and five on psychosocial stress were identified. All were published between 1973 and 2002. In spite of inconsistencies, the studies on nicotine indicated a greater risk of ADHD-related disorders among children whose mothers smoked during pregnancy. Contradictory findings were reported in the alcohol studies, and no conclusion could be reached on the basis of the caffeine study. Results from studies on psychological stress during pregnancy were inconsistent but indicated a possible modest contribution to ADHD symptoms in the offspring. Many studies suffered from methodological shortcomings, such as recall bias, crude or inaccurate exposure assessments, low statistical power, and lack of or insufficient control of confounders. A general lack of information on familial psychopathology also limited the interpretations.
CONCLUSIONS: Exposure to tobacco smoke in utero is suspected to be associated with ADHD and ADHD symptoms in children. Other maternal lifestyle factors during pregnancy may also be associated with these disorders. Further studies are needed to reach conclusions.