Neuropsychopharmacology: The Fifth Generation of Progress
for some subtypes of ADHD. Mick et al. found no evidence favoring the idea that putative viral exposure led to a nonfa- milial form of ADHD. In contrast, they found a weak trend toward an increase in winter births for children with ADHD who have a positive family history of ADHD. If replicated, this finding suggests that a seasonally mediated infection at birth may be an environmental ‘‘trigger’’ for the genetic predisposition to the disorder.
The delineation of psychosocial features in the child’s envi- ronment associated with more impaired outcome in chil- dren with ADHD has potentially important clinical, scien- tific, and public health implications. Such efforts can help to identify etiologic risk factors associated with more impaired outcome in ADHD and can characterize early predictors of persistence and morbidity of this disorder. Moreover, find- ing environmental risk factors for ADHD could help to design improved preventive and therapeutic intervention programs.
The classic studies by Rutter et al. of the Isle of Wight and the inner borough of London provide a compelling example of how psychosocial risk factors influence child psychopathology (186). Compelling examples of how psy- chosocial risk factors affect child psychopathology, these studies examined the prevalence of mental disorders in chil- dren living in two very different geographic areas. This re- search revealed six risk factors within the family environ- ment that correlated significantly with childhood mental disturbances: (a) severe marital discord, (b) low social class, (c) large family size, (d) paternal criminality, (e) maternal mental disorder, and (f) foster placement. This work found that it was the aggregate of adversity factors, rather than the presence of any single one, that impaired development. Other studies also found that as the number of adverse conditions accumulated, the risk of impaired outcome in the child increased proportionally (187). Biederman et al. found a positive association between Rutter’s index of adver- sity and ADHD, measures of ADHD-associated psycho- pathology, impaired cognition, and psychosocial dysfunc- tion (188).
Other cross-sectional and longitudinal studies have iden- tified variables such as marital distress, family dysfunction, and low social class as risk factors for psychopathology and dysfunction in children. For example, the Ontario Child Health Study in Canada showed that family dysfunction and low income predicted persistence and onset of one or more psychiatric disorders over a 4-year follow-up period (189). Other work implicated low maternal education, low social class, and single parenthood as important adversity factors for ADHD (171,190). These studies suggested that the mothers of children with ADHD had more negative communication patterns, more conflict with their children, and a greater intensity of anger than did control mothers.
Biederman et al. showed that long-term conflict, de- creased family cohesion, and exposure to parental psycho- pathology, particularly maternal psychopathology, were more common in ADHD-affected families compared with control families (191). The differences between children with ADHD and control children could not be accounted for by either socioeconomic status or parental history of major psychopathology. Moreover, increased levels of fam- ily-environment adversity predicted impaired psychosocial functioning. Measures indexing long-term family conflict showed a more pernicious impact on the exposed child than those indexing exposure to parental psychopathology. In- deed, marital discord in families has consistently predicted disruptive behaviors in boys (192). This research shows that the extent of discord and overt conflict, regardless of whether the parents are separated, predicts the child’s risks of psychopathology and dysfunction (193).
Thus, dysfunctional family environments appear to be a nonspecific risk factor for psychiatric disorders and psycho- logical distress. Reid and Crisafulli reported a metaanalysis of the impact of marital discord on the psychological adjust- ment of children and found that parental conflict signifi- cantly predicted a variety of child behavior problems (194). The Ontario Child Health Study provided a prospective example of the impact of parental conflict on children’s mental health: family dysfunction (and low income) pre- dicted persistence and onset of one or more psychiatric dis- orders over a 4-year period (189).
Low maternal warmth and high maternal malaise and criticism were previously associated with ADHD in children (195), and an epidemiologic study examining family attri- butes in children who had undergone stressful experiences found that children’s perceptions of mothers, but not fa- thers, differentiated stress-resilient and stress-affected chil- dren (196).
An extensive literature documents maternal depression as a risk factor for psychological maladjustment and psychi- atric disorder in children (197). This is consistent with the known familial link between ADHD and depression (79). Some investigators have suggested that depressed mood may lead mothers to perceive their children as more deviant than warranted by the child’s behavior. Richters, however, re- viewed 22 studies of this issue and concluded that, owing to methodologic problems with research in the area, there was no empiric foundation for this claim (198).
Other data revealed a link between maternal depression and child functioning that was independent of the mother’s perceptions. These data suggested that depressed mothers accurately perceive symptomatic behavior but react to it in a negative manner that worsens the condition of the child. This conclusion was echoed by Gelfand and Teti (197). Their comprehensive review of relevant literature found many studies to document the assertion that depressed mothers have attitudes of insensitivity, disengagement, dis- approval, and hostility toward their children. They also