Author
SINGER George H. S.;
Title
Meta-analysis of comparative studies of depression in mothers of children with and without developmental disabilities.
Journal citation/publication details
American Journal on Mental Retardation, 111(3), May 2006, pp.155-169.
Summary
This meta-analysis is confined to 18 studies carried out in the USA and Canada between 1984 and 2003, and shows a weighted effect size of .39 (in the small-to-moderate range) that indicates higher levels of depression in the mothers of children with developmental disabilities compared to mothers of children without disabilities. A parallel comparison of the percentages in each group that qualify as clinically depressed yields figures of 29% and 19% respectively. Although the former figure is cause for concern, the fact that over 70% of mothers of developmentally disabled children are not depressed both serves as a caution against blanket assumptions about the effects of parenting such a child, and suggests that preventive and treatment interventions could be of value.
Context
The existing research evidence on maternal depression provides mixed, and seemingly contradictory, findings on whether mothers of children with developmental disabilities are at higher risk. It is important to clarify matters because of the adverse effects of depression, to better understand the aetiology of depression in women in general, and to identify whether targeted services are needed for mothers of children with developmental disabilities.
Methods
What sources were used?
PsycINFO, PubMed, ERIC ( Education Resources Information Center ) and Dissertation Abstracts were searched for all available years using sets of subject terms. In addition, when journal titles were found with relevant papers, all issues appear to have been subsequently checked in the databases. Reference lists from reviews and selected papers were checked, and authors who had published two or more studies in the field were contacted. Authors of selected studies were also contacted for further data where necessary.
What search terms/strategies were used?
'All possible combinations' of the following sets of subject terms were used: 1) disability, developmental disability, handicap, autism, mental retardation. cerebral palsy, traumatic brain injury, spina bifida; 2) stress, depression, distress; 3) parents, mothers, families. Searches were limited to studies in the USA and Canada in case effect sizes might be influenced by the increase in early intervention and family support services in these two countries over the previous 20 years.
What criteria were used to decide on which studies to include?
Eligible studies covered mothers of children with developmental disabilities and a comparison group of mothers of children without disabilities. They also had to include data on depressive symptoms or general psychological distress, collected using published, standardised self-report measures. Studies were excluded if the comparisons were with population norms, if they provided insufficient data to calculate effect sizes, if the samples did not disaggregate data from mothers and fathers, and if they were later determined to be outliers because of unusually high effect sizes.
Who decided on their relevance and quality?
The searches delivered 358 papers, primarily from PsycINFO. No details of the filtering process are given but all procedures seem to have been carried out solely by the author except for coding and quality assessment of the finally selected studies, where a second researcher independently coded the entire set. Disagreements were resolved by discussion.
How many studies were included and where were they from?
Nineteen studies met the inclusion criteria, but one was subsequently excluded as an outlier because it reported an effect size eight time higher than the largest effect size in the others. Eighteen studies were thus analysed and, according to the inclusion criteria, all were from Canada or the USA . They comprised an overall sample of 6,641 mothers of children with developmental disabilities, and 26,438 mothers of children without disabilities. Table 1 summarises sample sizes, effect sizes, quality weightings and confidence intervals, while Table 2 presents descriptive information about the mothers and children with disabilities.
How were the study findings combined?
The author describes the statistical procedures used in some detail. Essentially, he conducted a form of meta-analysis known as fixed effect modelling.
Findings of the review
The overall weighted effect size produced by the meta-analysis was .39, considered to be in the small-to-moderate range, and this finding was 'relatively consistent' over the period from 1982 to 2003. It indicates that mothers of children with developmental disabilities are at higher risk of depression than their peers with non-disabled children, and that changes to service provision in North America between 1982-2003 had little effect, 'although they are likely to have had other benefits'.
A 'common sense, albeit, crude indicator' of the differences between these two groups of mothers is provided by comparing the percentages that fell on or above the cut-off point for clinical depression on two of the most commonly used diagnostic instruments. According to this analysis, 29% of mothers of children with developmental disabilities had elevated symptoms of depression, compared to 19% in the comparison group.
Investigation of potential moderating variables found that child age had a significant impact on effect size, with the mothers of disabled children more likely to have elevated depression levels than mothers of disabled adults. This indicates that maternal stress gradually declines over time, although the meta-analysis included only one study of adult children and none of adolescents. Further research is needed to establish more fully whether there is an age-related trend in depression among mothers. Autism proved to be a second moderating variable, with higher levels of depression associated with this condition than with mental retardation or spina bifida.
The quality of studies in the analysis was 'highly variable', with an average rating of 8.9 (range 3-12) on a scoring system (apparently not referenced) where 13 was the maximum. Future studies should try, if possible, to avoid the use of convenience samples and report demographic data more explicitly. Most of the studies relate to white, middle-class women, and more investigation is needed of minority ethnic and linguistic groups.
Authors' conclusions
Although it is a 'cause for further concern' that 29% of mothers of developmentally disabled children experience depression, promising preventive and treatment interventions, especially those using cognitive-behavioural approaches, do exist. Greater attention should be given to replication of these interventions, combined with rigorous evaluation, to build up a reliable evidence base on their effectiveness.
The author also notes that 'it is remarkable how little is known about the large majority of mothers of children with developmental disabilities who are faring as well, on average, as the rest of the women of child-bearing age in the United States'. While there is clearly a serious problem to be addressed, the fact that 71% of mothers of disabled children in the studies analysed did not experience depression 'should serve as a caution against blanket assumptions about negative impacts of parenting a child with disabilities'.
Implications for policy or practice
None are discussed.