BACKGROUND:
The aim of this systemic review and meta-analysis was to estimate the rates at which
oppositional defiant disorder (ODD) and conduct disorder (CD) occur in children and adolescents
with a diagnosis of autism spectrum disorder (ASD). Furthermore, the study aimed to explore
moderating factors which might influence prevalence rates of these co-occurring conditions
between studies.
METHODS:
A systematic search was conducted on August 10, 2020 using the PsycInfo and Medline
databases to identify relevant literature using key words and MeSH terms. Only studies of children
and adolescents aged between 3-25 were included in the meta-analysis. A modified Hoy’s risk of
bias tool was used to assess the bias of the included studies. Following the identification and
selection of relevant articles, a meta-analysis was conducted using R-studio software. Moderator
analysis was performed to explore whether participant characteristics and methodological design
of studies were associated with differences in reported ODD and CD prevalence rates. Potential
moderators included age, gender, intellectual ability, ethnicity, nationality, sample type, detection
bias, and sampling bias.
RESULTS:
Nineteen eligible studies were identified including a total sample of 6,085 individuals
with a diagnosis of ASD. The diagnostic rates of comorbid ODD and CD within the pooled sample
were 14.03% [95% CI 9.0-21.22] and 3.13% [95% CI 1.4-5.4] respectively. There was significant
heterogeneity in the rates of diagnosis between studies. Greater study bias was associated with
increased rates of co-occurring diagnoses. Recruitment bias moderated the prevalence of CD but
not ODD diagnoses. Detection bias moderated the number of ODD but not CD diagnoses. Study
demographics, sample type, and intelligence were not associated with the prevalence rate of
comorbidity found in the pooled sample.
DISCUSSION:
Study bias played a significant role over the rates of co-occurring CD and ODD
reported in the ASD population, yet the findings should be interpreted with some caution. The
meta-analysis was based on a predominantly Caucasian male sample and studies which used
DSM-IV criteria to assign diagnoses. This lack of participant heterogeneity limits the
generalizability of the study and underscores the importance of studying both population
characteristic and methodology in meta-analyses. Future research should explore the impact that
the updated DSM-5 have over co-occurring ODD and CD and focus on including more
minoritized populations
